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3 Introduction from the Director

5 LIFE SCIENCES

11 CHEMISTRY

19 MAGNET SCIENCE & TECHNOLOGY

27 CONDENSED MATTER PHYSICS

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2007YearinReview

Welcometoourannuallaboroflove.Attheendofeachyear,weaskMagnetLabusers

andourresearchfacultyattheFloridaStateUniversity,UniversityofFloridaandLosAlamos

NationalLabtosubmitone-pageabstractsoftheirMagLabresearchendeavors.AndI’msure

that a spontaneous hue and cry arises from a thousand voices:“We love doing this again

thisyear!”Surely,it’safairexchange:Magnettimeandexperton-sitecounsel,guidanceand

interpretation…inexchangeforaweeabstract.

Althoughyourpureloveofthisannualchorewouldbereasonenough,wealsocompile

thisinformationtogetasnapshotsummaryofresearchexperimentsunderway…ameasure

ofactivitythat isdifferent(andinmanywaysa leadingindicator)offuturepublicationsin

refereedjournals.

Wedoinfactappreciatethatalotofworkfromourusersandscientistsgoesintothis

issue.AfterwereceivethereportstheyarereviewedbytheMagLabScienceCouncil,which

hasthedifficultjobofdecidingwhichonestoforwardtomeforconsiderationashighlights.

Of the 407 reports submitted, 43 were recommended by the council. Of that number, I

picked32:fiveinlifesciences;seveninchemistry;seveninmagnetsandmaterials;and13in

condensedmatterscience.

SincerethanksgoestomembersoftheScienceCouncilfortheirthoughtfulconsideration.

They are: Albert Migliori (chair), Rafael Bruschweiler, Mark Emmett, Lev Gor’kov, David

Larbalestier,DenisMarkiewicz,DraganaPopovicandGlennWalter.

ThanksalsogotoKathyHedickforcat-herdingallofthereports–andus

–throughtheprocess.

The selection criteria emphasizes research that is

published, features new techniques for users, and showcases

outstandingresearchthattogetherspansallthreeMagLabsites

and seven user facilities. As such, these reports represent the

broadresearchportfoliooftheMagLabinaconciseformatfora

scientific,butnon-specialist,audience.

Many reports containing preliminary results

havebeenrecognizedaspromisingworktobe

followedcloselyin2008.

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Trying to reduce your

carbon footprint?

Signupforanonlinesubscriptionathttp://www.magnet.fsu.edu/mediacenter/publications/subscribe.aspx

Publishedby:National High Magnetic Field Laboratory1800EastPaulDiracDriveTallahassee,Florida32310-3706

Tel:850644-0311Fax:850644-8350

Mag Lab Director:GregBoebingerDirector of Public Affairs:SusanRayEditing and Writing: AmyMast,SusanRayGraphic Design: SavoyBrownThisdocumentisavailableinalternateformatsuponrequest.ContactAmyMastforassistance.Ifyouwouldliketobeaddedtoourmailinglist,pleasewriteusattheaddressshownatleft,call850644-1933,oremailwinters@magnet.fsu.edu

Greg Boebinger

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HerearethevitalstatisticsfortheResearchReports:

• In2007,407researchreportswerereceivedin17categories,

representing condensed matter physics, the life sciences,

chemistryandmagnetscienceandtechnology.

• 16% of the research activities in 2007 (64 reports) were

alreadypublishedin2007,manyinprominentjournals.

• An additional 6% of the reports were accepted for

publication;11%weresubmittedforpublication;and40%

havemanuscriptsinpreparation.

• ThemajorityofresearchprojectswerefundedbytheNational

Science Foundation, the Department of Energy, and the

NationalInstitutesofHealth.Otherfundingorganizations

included:theAmericanChemicalSociety;AmericanHeart

Association, Engineering and Physical Sciences Research

Council(UK),HumanFrontiersScienceProgram,IBM,Japan

SocietyforthePromotionofScience,MuscularDystrophy

Association, NASA, National Sciences and Engineering

Research Council (Canada), Russian Academy of Science,

U.S. Air Force Office of Scientific Research, U.S. Army, U.S.

GeologicalSurvey,U.S.EnvironmentalAgency,andtheU.S.

DepartmentofVeteransAffairs.

• The Magnet Lab’s User Collaboration Grants Program

(formerly and confusedly named the In-House Research

Program)supported48ofthe407researchactivitiesand

wastheprimarysupportfor24projects.Thisgrantprogram

promotes collaborations between internal and external

investigators,promotesboldbutriskyresearcheffortsand

providesinitialseedmoneyfornewfaculty,researchstaff

andfacilityenhancements.

Finally,eachofthe407userreportsandresultingpublications

is available on our Web site (magnet.fsu.edu/usershub/

publications).Youcansearchbyuserfacility,journal,firstauthor

orprincipalinvestigator.Inadditiontothe2006and2007user

reports and publications, you can pull up all MagLab user

reportssince2004andallpublicationsdatingbackto2000.

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N Internationalresearchersfromsuchdiversefieldsasecologytoneuroscienceareexploitingtheextremelyhigh mass specific sensitivity of the Magnet Lab’s 1-mm HTS cryogenic probe to characterize rare samplesfoundinecosystemsrangingfromtropicalrainforeststotheFloridaKeys.Oftentheseactivecompoundscanonlybeisolatedinsubmilligramquantitieshamperingstructureelucidation.InthereportbyMatthewet al.,thesensitivityofthisprobewasexploitedtoidentifynovelactivechemotypesandpharmacophoresproducedbycyanobacteria.TheyfoundthatextractsofLyngbya confervoidescollectedfromFt.LauderdaleandtheFloridaKeysyieldednovelproteaseinhibitorsthatarepotentinhibitorsofelastase.TheuseofthisHTS1-mmprobeisexpectedtoplayanincreasingroleindrugsdiscoveredfromraresamples. This work was published in the Journal of Natural Products (2007).

Exploiting Floridian MarinE CyanobaCtEria For drug disCovEryS. Matthew (UF, Medicinal Chemistry); K. Taori (UF, Medicinal Chemistry); J.C. Kwan (UF, Medicinal Chemistry); V.J. Paul (Smithsonian Marine Station); H. Luesch (UF, Medicinal Chemistry)

INTrODUCTIONThereisanurgentneedtoidentifynovelactivechemotypesandpharmacophoresasleadsforeffectivedrugdevelopmentinmanytherapeuticareas.Ourresearchisbasedonthehypothesisthatmarinecyanobacteriaareapotentialsourceofnovelbioactivecompounds.Thereissubstantialevidenceforthelargebiosyntheticcapacityofcyanobacteriatoproducechemicallydiversesecondarymetabolitesofbiomedicalutility.Floridaharbors possibly the most marine biodiversity in the continental United States, and therefore there is ahigh probability of discovering novel and intriguing structures. One major problem is that oftentimes onlysubmilligramquantitiesofactivecomponentscanbeisolated,hamperingstructureelucidation.

ExPErIMENTAL1H,13C,and2DNMRspectraforcyanobacterialmetaboliteswererecordedonBrukerAvanceNMRspectrometers(500MHz ,2.5mmprobe;600MHzwarmbore,5mmprobe;750MHz,2.5mmprobe)orBrukerAvance II600MHzspectrometerequippedwithNationalHighMagneticFieldLaboratory’s1mmtriple-resonancehigh-temperaturesuperconducting(HTS)cryogenicprobe.

rESULTS AND DISCUSSIONMarinecyanobacteriaofthegeneraSymplocaandLyngbyawerecollectedoffthecoastofFlorida,extractedandscrutinizedforcompoundswithbiomedicalutility.SeveralextractsofLyngbya confervoidescollectionsfromFt.LauderdaleandtheFloridaKeysyieldednovelproteaseinhibitors, lyngbyastatins4–7(Figure1),1,2whichdisplayedexceptionalpotencyininhibitingelastase. Activeextractcomponentswereisolatedbybioassay-guidedfractionationandanalyzedbyNMR(Figure1).Lyngbyastatins5and6wereisolatedinextremelylowyield(0.47and0.17mg,respectively),yetstructuredeterminationcouldbeachievedthankstothe1-mmHTScryogenicprobe.2

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Figure 1. 1H NMR and structure of lyngbyastatin 4 (left) and structures of all related metabolites, lyngbyastatins 4–7 (right).1,2

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CONCLUSIONSCyanobacteriacontinuetoyieldnewbioactivemetabolites.The1-mmprobewasessentialforthesuccessfulNMRanalysis.

ACkNOwLEDgEMENTSFloridaSeaGrantCollegeProgramNA06OAR4170014,ExternalUserProgramofNHMFLatAMRIS(NSF),andJ.Rocca.

rEfErENCES[1] Matthew,S.et al.,JournalofNaturalProducts,70,124-127(2007).[2] Taori,K.et al.,JournalofNaturalProducts,70,1593-1600(2007).

Multiply-labeled piscidin and HETCOR spectroscopy were successfully used to characterize themembrane-boundstructureandtiltofpiscidin1athighresolution.Accesstohighmagneticfieldsandlow-EprobesattheNHMFLenabledthiswork.

HigH-rEsolution nMr struCturE and tilt oF aMpHipatHiC pisCidin at tHE WatEr-bilayEr intErFaCEriqiang Fu (NHMFL), Eric Gordon (Pacific Lutheran University, Chemistry), Milton Truong (NHMFL), Mallorie Taylor (PLU), Jeff Ditto (PLU) and Myriam Cotten (PLU)

INTrODUCTIONThis research combines several solid-state NMRtechniques to obtain the high-resolution structureof membrane-bound piscidin 1 (p1)1 and helpestablish relationships between its structural motif,interactions with biological membranes, potency,andmechanismsofaction.Piscidin1,anamphipathiccationic antimicrobial peptide from fish, belongs toa large familyofhost-defensepeptides that interact,at least initially, with cell membranes in order toperform their function. A bottleneck in this area ofresearch is the lack of atomic level information onpeptide-lipid interactions due to the challenges ofperforming traditional methods on physiologicallyrelevantsamples.Usingsolid-stateNMR,wepreviouslydemonstrated that piscidin adopts an in-plane -helical conformation in the presence of hydratedphospholipidbilayers.2

Here,weused2DHETCOR(Heteronuclearcorrelation)spectroscopy3 to obtain the structure of membrane-bound piscidin. HETCOR correlates not only theorientation-dependent 15N chemical shifts and 1H-15N heteronuclear dipolar couplings as in PISEMA(Polarization inversion spin exchange at the magicangle)4,butalsothe1Hchemicalshiftrestraintsfrompeptideplanes.SimilarlytoPISEMA,HETCORdatacanbedirectlyanalyzedtoobtaintilt,polarity,andhigh-resolutionstructuresof-helices.

ExPErIMENTALHETCORexperimentswerecarriedoutontheultra-widebore900MHzandBrukerAvance600MHZWBNMRspectrometers.

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Figure 1.Molecular model and 15N NMR spectra of uniformly aligned DMPC/DHPC bicelles containing U-15N-labeled cytb5 (black) and U-15N-labeled cyt b5 with cyt P450 complex (red) at 37°C. The model (A) shows cyt b5-cyt P450 complex and the model (B) shows cyt b5 in the context of a DMPC bilayer; the transmembrane, linker, and heme-carrying soluble domains are evident. 15N NMR spectra are absence (C-F, black) and presence (C-F, red) of cyt P450. Different spectral shapes are observed in (C) RINEPT experiments and cross-polarization (CP) experiments at contact times of (D) 3.0 ms, (E) 0.8 ms, and (F) 0.1 ms report on the different mobilities of the three domains of the cyt b5 molecule. The 15N RINEPT shows spectral intensity only in the 100-130 ppm region, consistent with a high mobility of the soluble domain. In the RINEPT sequence, 2.6 and 1.3 ms were used in the first (before the pair of 90o pulses) and second (after the pair of 90o pulses) delays, respectively.

rESULTS AND DISCUSSIONHigh-resolutionHETCORspectrawereobtainedfrommultiply15N-backbonelabeledamidatedp1(p1-NH2)inthepresenceofaligned3:1phosphocholine/phosphoglyceratebilayers5.AsshowninFigure 1,analysisofdatafrom18sitesofthis22-merrevealsthepresenceoftwohelicalsegments(tilts=88and82º)separatedbyakink(~6º)atGly13.Thiskinkmayhelponeportionofthepeptideinsertmoredeeplyinthehydrophobiclipidbilayerandthismayberelatedtothemechanismofmembranedisruption.

CONCLUSIONSMultiply-labeled piscidin and HETCOR spectroscopy were successfully used to characterize the membrane-boundstructureandtiltofpiscidin1athighresolution.Accesstohighmagneticfieldsandlow-EprobesattheNHMFLfacilitatedthiswork.

ACkNOwLEDgEMENTSWeacknowledgesupportfromtheDreyfusFoundation,ResearchCorporation,andCambridgeIsotopeLaboratories.

rEfErENCES[1]a)Silphaduang,U.;Noga,E.J.Nature.2001,414,268.b)Lauth,Xet al.J.Biol.Chem.2002,277,5030.[2]a)Chekmenev,E.Y.,et. al.J.Am.Chem.Soc.2006,128,5308.b)Chekmenev,E.Y., et. al.Biochim.Biophys.Acta.2006,1758,1359.[3]Fu,R.;Truong,M.;Saager,R.J.;Cotten,M.;Cross,T.A.J.Magn.Reson.2007,188,41.[4]Wu,C.H.;Ramamoorthy,A.;Opella,S.J.J.Magn.Reson.A.1994,109,270.

2D HIMSELF spectra were recorded on bicelles containing uniformly 15N-labeled cytochrome b5 at900MHzwithandwithoutunlabeledcytP450.SpectraareremarkablyresolvedandPISAwheelsfromthetransmembraneregionarewellidentifiable.Structuralanddynamicschangesintherigidtransmembraneregionofcytb5inthepresenceofcytP450areobserved.Theseresultswillopennewapproachestostudythestructureanddynamicsofcytb5aswellasthecytb5-cytP450complex.

tHE struCturE and dynaMiCs oF MEMbranE-bound CytoCHroME b5 – CytoCHroME p450 CoMplEx by MEans oF solid-statE nMr spECtrosCopyKazutoshi Yamamoto, Jiadi Xu, Sang-Choul im, Lucy Waskell, and Ayyalusamy ramamoorthy (University of Michigan)

INTrODUCTIONProtein science in the post-genomic era is beginning todirect its course towards theelucidation of protein-proteininteractions. Many biologicallyimportant protein-proteininteractions, such as signaltransduction,electrontransportchainandphotosynthesis,takeplace on the surface or acrossthe lipid membrane of livingcells. Despite their importanceand ongoing investigativeefforts,therehavebeenveryfewreportsontheproteinstructuredeterminationofthecomplexescomposed of protein-protein interactions and lipidbilayers. Practicable methodswere deemed necessary tocharacterize the structure of complex protein systems due to the difficulties associated with membraneproteins in general and membrane protein-protein complexes in particular.We carried out the first studies

Figure 1.Plots of experimental 15N chemical shifts (top), 15N-1H dipolar couplings (middle), and 1H chemical shifts (bottom) vs. residue number for p1-NH2. Simulated waves are provided in red and blue.

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on an intact mammalian membraneprotein complex, rabbit cytochromeb5(cytb5)andcytochromeP4502B4(cyt P450), in a membrane bilayerenvironmentbymeansofsolid-stateNMR at the atomic-level.1 Cyt b5activates the enzymatic function ofcytP450tooxidizeawidevarietyofpharmaceutical compounds.2,2 Sincethe oxidation of pharmaceuticalcompoundsisofgreatimportancetounderstandingtheirin vivoefficiency,there is considerable interestin understanding the interaction and function of the cyt b5-cyt P450 complex. Cyt b5 is a 16.7 kDa proteinconsistingofthreedomains:aglobularcytosolicdomainconsistingofahemedomain,ashortlinkerregionandatransmembranedomain.Thetransmembranedomainand linker region,whichhavebeenpreviouslyinaccessibletostructuralstudies,areabsolutelyessentialtoactivatecytP450.

ExPErIMENTAL15NNMRwasperformedonaUWB900MHzNMRspectrometer(atNHMFL)equippedwithanNHMFLLow-Eprobe.TheLow-EprobeandhighermagneticfieldwereusefulforthisstudybecausetheintactcytP450proteinisheatsensitive.Spectralacquisitiontimewas18hoursfortwo-dimensionalstatic15N-HIMSELF3experimentsat30oC.

rESULTS AND DISCUSSION:2D HIMSELF spectra were recorded on bicelles containing uniformly 15N-labeled cyt b5 with and withoutunlabeledcytP450(Figure2).SpectraareremarkablyresolvedandPISAwheels4fromtheTMregionareclearlyseen. Here, we found structural and dynamics changes in the rigid transmembrane region of cyt b5 in thepresenceofcytP450.Weexpecttheseresultswillopennewapproachestostudythestructureanddynamicsofcytb5aswellasthecytb5-cytP450complex.

rEfErENCES[1]U.H.N.Dürr,L.Waskell,A.Ramamoorthy,Biochim.Biophys.Acta.Biomembranes,doi:10.1016.[2]U.H.N.Dürr,K.Yamamoto,S.-C.Im,L.Waskell,A.Ramamoorthy,J.Am.Chem.Soc.129(2007)6670-6671.[3]K.Yamamoto,S.V.Dvinskih,A.Ramamoorthy,Chem.Phys.Lett.419(2006)533-536.S.V.Dvinskikh,K.Yamamoto,A.Ramamoorthy,

J.Chem.Phys.125(2006)034507.[4]J.Wang,J.Denny,C.Tian,S.Kim,Y.Mo,F.Kovacs,Z.Song,K.Nishimura,Z.Gan,R.Fu,J.R.Quine,T.A.Cross,J.Magn.Reson.

144(2000)162-167

Itmightcomeasahugesurprisethatinsectsecretionscouldbethesourceofthenextanti-canceragent.InareportbytheUniversityofFloridaEdisonlab,thatisexactlywhattheyfound.UsingahighlysensitiveHTS1mmprobe,theydeterminedthatthedefensivesecretionofParectatosoma mocquerysi,awalkingstickinsect from Madagascar, contains glucose, water, and a new monoterpene, parectadial, (4S)-(3-oxoprop-1-en-2-yl)cyclohex-1-enecarbaldehyde.Parectadialwasalsofoundtobehavesimilararlytoananti-canceragent,inthatatasingleconcentrationitinhibitsthegrowthofseveraldifferentestablishedcancercelllines.ThisstudywasmadepossibleusingtheNHMFL’s1-mmHTSprobe.Thisprobehasproventobecomeanextremelyefficientinstrumentfornaturalproductdiscoveryduetoitshighsensitivitywhenusingextremelysmallamountsofmaterialcomparedtoconventionalprobes. This work was published in the Journal of Natural Products (2007).

parECtadial: a novEl MonotErpEnE FroM Parectatosoma mocquerysiA. T. Dossey (UF, Biochemistry); S. S. Walse (USDA Laboratory); o. Conle (Bolsterlang, Germany); A. S. Edison (UF, Biochemistry)

iNTroDUCTioNTheNHMFL1-mmHTSprobeinAMRIShasbeenagreatassetfornaturalproductstudies.1Usingthisprobe,

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the defensive secretion of Parectatosoma mocquerysi Finot 1897, a walkingstick insect from Madagascar,wasdeterminedtocontainglucose,water,andanewmonoterpene,parectadial,(4S)-(3-oxoprop-1-en-2-yl)cyclohex-1-enecarbaldehyde. This work demonstrates the utilityof the 1-mm HTS probe and the value of walkingstick insects assourcesofnewbioactivecompounds,andprovidesananalyticalframeworkforidentifyingsuchsubstances.2

ExPErIMENTAL, rESULTS AND DISCUSSIONP. mocquerysi was kept in culture by O. Conle (Figure 1), and thesprayfrom5insectswascollectedandsenttotheAMRISfacilityforanalysis.Weusedavarietyofmassspectrometry,chromatography,and NMR techniques to show that the spray consists of glucoseand a novel monoterpene that we named parectadial (Figure 2).Weshowedbychemicalsynthesisandenantioselectivegaschromatographyandcirculardichroismthatinsectproducesonlythe“S”isomerthatisshowninFigure2.Anisomorpha buprestoides,awalkingstickfoundinFlorida,producesavariablemixtureofmonoterpenesthathavea5memberedring2,3 ratherthanthe6memberedringofparectadial.4

Basedonsimilaritiestootherchemicalsthathavebeenshowntokillcancercells,wehavetestedparectadialforanti-canceractivity.AtasingleconcentrationitinhibitsthegrowthofseveraldifferentcancercelllinesattheNationalCancerInstitute’s60celllinescreenandiscurrentlyinthesecondroundoftestingtoevaluateadoseresponse.

CONCLUSIONSTheNHMFL1-mmHTSprobeisanextremelyefficientinstrumentfornaturalproductdiscovery,becausemuchlessmaterialisneededthanforconventionalprobes.

ACkNOwLEDgEMENTSBillBrey(NHMFL),SaikatSaha(NHMFL,nowGE)RichWithers(Bruker,nowVarian),andRobNast(Bruker,nowVarian)madethe1-mmHTSprobe.FundingwasfromtheHFSP,NIH,andNHMFL.

rEfErENCES[1] Brey,W.W.,Edison,A.S.,Nast,R.E.,Rocca,J.R.,Saha,S.,andWithers,R.S.(2006)Design,construction,andvalidationofa1-mm

triple-resonancehigh-temperature-superconductingprobeforNMR.JMagnReson179,290-3.[2] Dossey,A.T.,Walse,S.S.,Rocca,J.R.,andEdison,A.S.(2006)SingleInsectNMR:ANewTooltoProbeChemicalBiodiversity.

ACSChemicalBiology1,511-514.[3] Zhang,F.,Dossey,A.T.,Zachariah,C.,Edison,A.S.,andBruschweiler,R.(2007)Strategyforautomatedanalysisofdynamic

metabolicmixturesbyNMR.Applicationtoaninsectvenom.AnalyticalChemistry79,7748-7752.[4] Dossey,A.T.,Walse,S.S.,Conle,O.V.,andEdison,A.S.(2007)Parectadial,aMonoterpenoidfromtheDefensiveSprayof

Parectatosomamocquerysi.JNatProd70,1335-1338.

By utilizing two low energy fragmentation techniques on peptides, it is now possible to assign thepeptidefragmentsasoriginatingfromeithertheN-terminusorC-terminusofthepeptideparent,whichwillgreatlyfacilitatethesequencingofpeptides/proteinsinthegasphase. This work was published in analytical chemistry (2007).

burning tHE CandlE at botH Ends: protEin sEquEnCing FroM tHE n- and C-tErMiniYury o. Tsybin (NHMFL Tallahassee), Mark r. Emmett (NHMFL Tallahassee; FSU Chemistry & Biochemistry), Christopher L. Hendrickson (NHMFL Tallahassee; FSU Chemistry & Biochemistry), and Alan G. Marshall (NHMFL Tallahassee; FSU Chemistry & Biochemistry)

INTrODUCTIONThe most sensitive and informative way to determine the amino acid sequence of a protein is to slice itinto segments with a suitable enzyme in solution, then“electrospray” it into the gas phase (i.e., remove all

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Figure 2Two-dimensional static 15N-HIMSELF spectra of TM region of a free U-15N-cytb5 (black) and the protein-protein complex U-15N-cyt b5 with cyt P450 (red) in bicelles.

Figure 2.Parectadial: (4S)- (3-oxoprop-1-en- 2-yl)cyclohex-1-enecarbaldehyde.

Figure 1.Adult male Parectatosoma mocquerysi.

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Figure 1.HFEPR spectrum of 1 at 846 GHz and 5 K (black trace) with its powder-pattern simulation (red trace). Simulation parameters: S = 1, D = +26.9 cm–1, E = +0.095 cm–1; gx,y = 2.1; gz = 2.04.

surroundingwatermoleculesandaddpositivechargesintheformofprotons),andfinallybreakitatvariousbackbonepositionsandweightheproductpeptideswithamassspectrometer.Themassdifferencebetweenproductpeptidesresultingfromcleavageatconsecutivelinkagesthenidentifiestheaminoacidbywhichtheydiffer.Untilnow,ithasnotbeenpossibletodeterminewhichendoftheoriginalpeptideiscontainedinthechargedfragment,leadingtoambiguousidentification.

rESULTS AND DISCUSSIONNHMFLscientistshavesolvedthatproblembyshowingthatapeptidebreaksintotwotypesoffragments,withrelativeabundancesthatdependontheenergyoftheelectron“bullets”causingthefragmentation.Thus,byperformingthefragmentationateachoftwodifferentelectronenergies,itispossibletodeterminewhetherthefragmentionisN-(amino-)terminalorC-(carboxyl-)terminal(“c”or“z”intheFigure).Proteinidentificationisthusnowtwiceaseasyasbefore.

ACkNOwLEDgEMENTSThisworkwassupportedbytheNSFNationalHigh-FieldFT-ICRMassSpectrometryFacility(DMR00-84173),FloridaStateU.,andNHMFL.

rEfErENCES[1]Tsybin,Y.O.;et al.,Anal.Chem.79,7596-7602(2007).

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Iron (Fe) is the most important transition metal in biology. Oxygen molecules (O2) bind to Fe inhemoglobintobetransportedthroughoutthebodyviathebloodstream.Oxygenalsoisstoredinmuscletissuebybeingboundtoironinmyoglobin,anotherhemeprotein.Inthesecases,ironitselfisnotinvolvedinchemicalreactions.However,therealsoexistbiomolecules,onlyrecentlydiscovered,knownasnon-hemeironenzymes.Intheseenzymes,oxygenmoleculesareactivatedbyirontocreateahighlyreactive“ferryl”species,[FeO]2+,whichthenreactswithvarioussubstratestoproducebiologicallyimportantmolecules.Veryrecently,stablesmallmoleculeanalogsofthisenzymeactivespecieshavebeensynthesized.Wehavenowstudiedtwoofthesemoleculesbyhigh-frequencyandhigh-fieldEPR(HFEPR)atNHMFL.HFEPRisuniquelysuitedforthestudyofthesesystems,duetotheirunusualelectronicspinstructure,andthebestdescriptiontodateofthisaspectoftheferrylunitisnowavailable.Thisinformationisofgreatimportancetosyntheticchemistsintermsofhelpingthemdesignbetterfunctionalanalogstotheenzymes.ItisimportantalsotobiochemistsindemonstratingtheapplicabilityofexperimentalmethodspresentatNHMFLtotheenzymesthemselves. Lastly, the specific electronic structure information provided is important to computationalchemistswhoaretryingtounderstandthecorrelationbetweenelectronicstructureandreactivityinbothsmallmoleculesandinnon-hemeironenzymes.Thusfar,theenzymesaremuchmorereactivethantheirsyntheticanalogs,butthebasisforthisisnotwellunderstood. The work was supported by the user collaboration Grants Program and is currently in press in inorganic chemistry (2008).

HFEpr studiEs on FErryl CoMplExEs rElEvant to HEME and non-HEME iron EnzyMEsK. ray, J. England, L. Que, Jr. (U. of Minnesota, Chemistry); A. ozarowski, D. Smirnov, J. Krzystek (NHMFL); J. Telser (roosevelt U., Chemistry)

INTrODUCTIONNon-heme iron enzymes are widely found inbiologyandperformabroadrangeoffunctions,particularlyactivationofdioxygenandsubsequentoxidativechemistry.1Considerableefforthasbeendevoted to their spectroscopic characterization,by a variety of techniques including MCD andMössbauerspectroscopies,aswellasconventionalEPR. In parallel, synthetic efforts have led to theisolationandcharacterizationofmodelcomplexesfornon-hemeenzymes.2

The currently accepted model for the action ofnon-heme iron enzymes is via a ferryl ([FeIVO]2+)intermediate.1,2TheelectronicspingroundstateofferrylspeciescanbeeitherS=2,orintermediatespinS=1.ModelcomplexeshavethusfarexhibitedS=1groundstates;2however,surprisinglyaS=2groundstatehasbeenobserved for the reactiveferryl intermediate in a non-heme iron enzyme.1Thebasisforthisdifferencebetweenenzymeandmodel compounds is of great interest. As a steptoward understanding this difference, we haveappliedHighFrequencyEPRtostudytwostableferrylcomplexesinthesolidstate:[FeO(tmc)(CH3

CN)](CF3SO3)2(1)and[FeO(N4py)(CH3CN)](CF3SO3)2(2),wheretmcistetramethylcyclam(1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane)andN4pyisbis(2-pyridylmethyl)bis(2-pyridyl)methylamine).2

ExPErIMENTALTheNHMFLMm-andSub-mmWaveFacilitywiththeresistive(“Keck”)25-Tmagnet,andtheEMRFacilitywiththesuperconducting17-Tmagnetwereusedtostudypolycrystallinesamplesof1and2.

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rESULTS AND DISCUSSIONAnHFEPRspectrumof1isshowninFigure1.Thefieldvs.frequencydependenceoftheobservedresonancesconfirmthetriplet(S=1)groundspinstatecharacterizedbyazfsparameter|D|of~27cm–1andsmallrhombicity(E~0).AcomputerfitofthisentiredatasetprovidedcompletespinHamiltonianparametersasgiveninFig.1caption.Similarresultswereobtainedfor2,althoughthezfswassignificantlysmaller(D=+22.0cm-1).

CONCLUSIONSThisstudyisthefirstapplicationofHFEPRtotheferryl([FeIVO]2+)ion,whichisofgreatrelevancetobiologicaloxidationprocessesbyiron-containingenzymes.Fromatechnologicalandmethodologicalpointofview,thestudyissignificantinthatanewhighvalueforzero-fieldsplittingofthetripletspinstate(nearly30cm-1)hasbeendirectlymeasuredbyHFEPR.

ACkNOwLEDgEMENTSWethanktheNHMFL-IHRPProgram,RooseveltUniversity,andNIH(GM-33162toLQ)forsupport.

rEfErENCES[1]Krebs,C.,et al.,Acc.Chem.Res.40,484-492(2007).[2]Costas,M.,et al.,Chem.Rev.104,939-986(2004).

Polymeric heterometallic compounds with properties potentially useful in the areas of magnetism,catalysisandelectricalconductivityhavebeenextensivelystudiedinrecentyears.Whileimportantfromatheoretialviewpoint,theymayalsogiveinsightintothemetal-metalinteractionsinbiologicalsystemslikemetalloenzymesthatcontainexchange-coupledparamagneticmetal ions. Inthiswork,asupramolecularsystemcontaininginfinitechainsofbinuclearanions[Mn2(succ)2Cl2]2-(succisthedianionofsuccinicacid)wassynthesized.Thesechainsarelinkedtogetherby[Cu(en)2]2+cations(en=ethylenediamine)toformanextendedtwo-dimensionalnetwork.Spectra expected for the anions and cations above were observed in high-field and –frequency EPR.However,additionalweaksignalswerealsoseenthatallowedtoprovethepresenceof8%ofa‘swapped’systemcontaining[MnCu(succ)2Cl2]2-anionsand[Mn(en)2]2+cations.Thesespecieseludeddetectionbyx-raycrystallography.Ontheotherhand,largezero-fieldsplittinginbinuclearMn-CuandMn-Mnfragmentsrendered classical EPR useless. High-field and –frequency EPR is thus the only method indicating thisinterestingimperfectnessofthesyntheticmethodapplied. This work is currently in press in inorganic chemistry (2008).

dirECt syntHEsis, Crystal struCturEs, HigH-FiEld Epr and MagnEtiC studiEs oF HEtEroMEtalliC polyMErs Containing Mn(ii) CarboxylatEs intErConnECtEd by [Cu(en)2]2+

V. G. Makhankova, A. o. Beznischenko, V. N. Kokozay (Kiev U., Chemistry); r. i. zubatyuk, o. V. Shishkin (National Academy of Sciences, Kharkiv, Ukraine); J. Jezierska (Wroclaw U., Poland, Chemistry); A. ozarowski (NHMFL)

INTrODUCTIONA novel synthetic strategy has been developed to directly obtain heterometallic polymeric coordinationcomplexes in a‘one-pot’ reaction. In this work the magnetic properties and High-Field EPR spectra of thecompound[Cu(en)2][Mn2(succ)2Cl2]containingchainsofdimeric[Mn2(succ)2Cl2]2+anionslinkedby[Cu(en)2]2+cations,(en=ethylenediamine),werestudied.

ExPErIMENTALHigh-frequencyEPRspectraupto413GHzwererecordedonthetransmissionspectrometerattheEMRfacilityoftheNHMFL.MagneticsusceptibilitydataofapowderedsampleweremeasuredwithaSQUIDmagnetometer(QuantumDesignMPMSXL-5)overthetemperaturerange1.8–300Katthemagneticinductionof0.5T.

rESULTS AND DISCUSSIONThedominantfeatureofthelow-temperaturehigh-fieldEPRspectrawasanaxially-symmetricspin-triplet(S=1)signalcharacterizedbyisotropicgfactorequalto2andthezero-fieldsplittingparameterDof-3.046cm-1.ADMnvalueforseparateMn(II)ions(S=5/2)of+0.38cm-1wasdeductedfromthesedataandsatisfactorilyreproduced

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TRY byusingaDensityFunctionalTheorycalculation1thatresultedinDMn=+0.32cm-1.Additionalsignalsseenin

EPRspectraaswellasmagneticsusceptibilitydataallowedtoconcludethatthe‘one-pot’syntheticmethodproduced92%oftheintendedcomplex[Cu(en)2][Mn2(succ)2Cl2],whileintheremaining8%theMn(II)andCu(II)ions were‘swapped’ to form a [Mn(en)2][MnCu (succ)2Cl2] system.The magnetic susceptibilities of the maincomplex()andthatofthe‘swapped’system(sw)wereexpressedas

andtheexchangeintegralJMn-Mnmagnitudeof32cm-1wasfoundfromfittingprocedures.TheDFTcalculation(‘broken-symmetry’approach)resultedinJMn-Mn=44cm-1,inareasonableagreementwithexperiment.

CONCLUSIONSMagnetic susceptibility measurements and high-frequency EPR studies proved the absence of exchangeinteractionsbetween[Cu(en)2]2+unitsandMnII-carboxylateanions,whilethemanganeseionsinthedimericanionwerefoundtobeexchange-coupled.Thesingle-ionDMnwassatisfactorilyreproducedbyaDFTcalculationusing the ORCA software package,1 as was the exchange integral magnitude JMn-Mn.The magnetic and EPRresultsindicatethatthe‘one-pot’synthesiswashighly,butnotperfectlyefficientinputtingmanganeseandcopperionsindesiredlocations.

ACkNOwLEDgEMENTSThisworkwassupportedinpartbyINTAS(projectYS05-109-4488)andbytheNHMFL.TheNHMFLisfundedbytheNSFthroughtheCooperativeAgreementNo.DMR-0084173andtheStateofFlorida.

rEfErENCES[1]Neese,F.ORCA–anabinitio,DFTandSemiempiricalProgramPackage,Version2.6-04,2007;UniversitätBonn:Bonn,Germany

Instrumentation at the Magnet Lab is allowing for the study of diffusion on the nanoscale in modelsystems.SandersandVasenkovhaveperformednon-invasivestudiesoflipidself-diffusioninmembranesonthenanoscaleusingNMRspectroscopycombinedwithpulsedfieldgradientsupto35T/mgradientamplitudes(see Report #123, http://www.magnet.fsu.edu/usershub/publications/researchreportsonline.aspx). Theirstudiesdemonstratethatitispossibletomonitoranomalousdiffusioninlipidbilayersdepositedonorientedglassstacksat750MHzandoverlengthscalesassmallas100nm.Usinganotherapproach,theBowerslabhasdevelopednovelapproachestofollowdiffusionofhyperpolarizedXeatomsastheyneartheopeningsofself-assembledL-Alanyl-L-Valinedipeptidenanotubes.Inthecurrentreport,ChengandBowerreportanewmethod to provide greater accuracy in rate constant determination, and facilitate measurement of smallerexchangerateconstants.Thisallowsforthedeterminationofslowerexchangeprocessesorlongerdiffusiontime/lengthscalesforinthedepthcharacterizationofnanotubesornanoporousmaterialsingeneral.• This work was supported by the Magnet Lab’s user collaboration Grants Program and published in the Journal of the american chemical society (2007).

intErruptEd gas FloW to EnHanCE Cross-pEak nMr signals in HypErpolarizEd xEnon gas: a nEW tECHniquE For studying nanosCalE diFFusionC.-Y. Cheng, J.P. Pfeilsticker and C.r. Bowers, Department of Chemistry, University of Florida

INTrODUCTIONInourrecentJACSarticle1wepresentedastudyoftheexchangekineticsofXeatomslocalizedneartheopeningsofself-assembledL-Alanyl-L-Valine(AV)dipeptidenanotubes2,3utilizingcontinuous-flowhyperpolarized2D-EXSYNMR.InCFHP2D-EXSY,hyperpolarizedgasistransportedfromtheopticalpumpingcelltothesamplespaceataconstantflowrate,enablingtherapidacquisitionof2Dspectrawithenhancedsensitivity.Inderivingtheexpressionsforthecross-peaksignalsunderflowconditions,wenotedthatthefiniteresidencetimeofthehyperpolarizedgasinsidethesamplespacemaysuppressdiagonal-andcross-peaksignals,andwesuggestedthattheundesiredsignalsuppressioncouldbemitigatedsimplybyinterruptingthegasflowduringthemixingtimeofthe2D-EXSYpulsesequence.1HerewepresentthedramaticexperimentalconfirmationofthiseffectinAV.

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Figure 1.Low E probe showing stator and tuning network.

Figure 1.Gas-flow attenvation intensifies NMR exchange signals (GAINES). Hyperpolarized xenon-129 EXSY spectra in AV nanotubes acquired under continuous (right) and interrupted gas flow conditions using a mixing time of 1s. Spectra were acquired at -10ºC at 9.4T.

ExPErIMENTALA15mgAVsamplewasevacuatedin-situto~10-5torrat100ºCfor2-3hourspriortoexperiments.Thegasmixtureconsistedof2%129Xe,2%N2and96%4Heatatotalpressureof4600mbar.Afractionalnanotubeoccupancyof=0.047wasinferredfromtheXeshifttensor.Thecontinuous-flowhyperpolarized129XeNMRsetupisthesameasthatdescribedinRef.1,exceptforonemodification:theoutletofthesamplespacewasconnectedtoatwo-waysolenoidvalve.AnauxiliaryTTLgateontheBrukerspectrometerwasusedtoswitchthesolenoidvalvefromthepulseprogramtostoptheflowofgas.

rESULTS AND DISCUSSIONTheCFandIFmodehyperpolarized129Xe2D-EXSYspectraacquiredinAVnanotubesatm=1sarepresentedbelow. The continuous-flow sequence barely yielded any cross-peaks. In contrast, the IF mode spectrumexhibits intensegasphasediagonal and exchangecross-peak signals. Thus,by interrupting the gasflowduringtheEXSYpulsesequence, the cross-peaksignals were enhanced byafactorof~60.4

CONCLUSIONSOur new methodwill provide greateraccuracy in rate constantdetermination, andfacilitate measurementof smaller exchangerate constants. It may also be applicable to other hyperpolarized species such as 1H or 13C generated fromparahydrogenorDNP.Theabilitytoprobelongermixingtimeswillfacilitateextensionofhyperpolarized2D-EXSYtoslowerexchangeprocessesorlongerdiffusiontime/lengthscalesforcharacterizationofnanotubesornanoporousmaterialsingeneral.

ACkNOwLEDgEMENTSConstructionoftheXenon-129polarizerwassupportedbytheNHMFLIn-HouseResearchProgramandUF.

rEfErENCES[1]C.-Y.ChengandC.R.Bowers,J.Am.Chem.Soc.129,13997-14002(2007).[2]I.Moudrakovskiet al.Proc.Natl.Acad.Sci.U.S.A.101,17924-17929(2004).[3]C.-Y.ChengandC.R.Bowers,ChemphysChem,82077–2081(2007).[4]C.-Y.Cheng,J.P.PfeilstickerandC.R.Bowers,J.AmChem.Soc.130,2390-2391(2008)

AsignificantandcleveradvanceinMASNMR,“Theprobecurrentlyoutperformscommercialprobeswehavetestedaswellasresultspublishedforotherdesigns.”Addscapabilitytotheuserprogramandthefieldaswell.Ithasalreadybeenusedfornewmeasurementsdescribedbytheauthorsinanotherreport.• This work was supported by the User collaboration Grants Program and was published in magnetic resonance in chemistry (2007).

loW-E MagiC anglE spinning probE For biologiCal solid statE nMr at 750 MHzP.L. Gor’kov, W.W. Brey (NHMFL/FSU); S. McNeill (UF Electrical and Computer Engineering); J.r. Long (UF Biochemistry and Molecular Biology)

INTrODUCTIONCrossed-coilNMRprobesareauseful tool for reducingsampleheatingforbiologicalmagicanglespinning(MAS) NMR. In a crossed-coil probe, the higher frequency 1H field, which is the primary source of sampleheatinginconventionalprobes,isproducedbyaseparatelow-inductanceresonator.Becauseasmallerdrivingvoltageisrequired,theelectricfieldacrossthesampleandtheresultantheatingisreduced.Inacommercial

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aMASprobebasedonthealternativeapproachofplacingthe1Hresonatoroutsidethesolenoid(Figure1).Becausethesolenoidcanthenbesmallerandbetterseparatedfromthe1Hresonator,weexpectthatthisapproachwillgiveimprovedsensitivityandallowhigherB1fieldswithoutarcingbetweenthetwocoils.Thisdualresonatorapproach,named“Low-E,”wasoriginallydevelopedtoreduceheatinginsamplesofmechanicallyalignedmembranes2,whereitallowedtheuseoflargersamplesthatwererequiredtoobtainsufficientNMRsignal.Thestudyofinherentlydilutesystems,suchasproteinsinlipidbilayers,viaMAStechniquesalsorequireslargesamplevolumesathighfieldtoobtainspectrawithasufficientsignalto noise ratio under physiologically relevant conditions.Thisyear we tested the probe under a variety of conditions, finetuningdesignelementstoimproveprotondecouplingfields.The probe currently outperforms commercial probes wehavetestedaswellas resultspublished forotherdesigns. Inparticular,duetothe largervolumeoftherotor,weareableto examine structures in membrane associated peptides atphysiologicallyrelevantconcentrations.

METhODSTheprobewasthoroughlycharacterizedinordertodeterminemaximumachievableB1fields,homogeneityoftheB1fields,RFefficiencies,RFheating,frictionalheatingunderMAS,spectrallinewidths,andsignal/noiseonstandardcompounds.WorkingwithRevolutionNMR(Ft.Collins,CO),wewereabletoobtainrotors which have thinner walls and spin stably at 12 kHz,allowingustopackmoresample intotherotors.To increaserobustnessontheprotonchannel,capacitorswereadded inparalleltoreducevoltagesatindividualpoints.ThiscausedasmalldecreaseinRFefficiencybutallowsustooperateforlongperiodsoftimewithhighprotondecoupling.

rESULTS AND DISCUSSIONUndernormaloperatingconditions,a1HB1fieldof93kHzandhomogeneity(810°/90°)of93%canbeobtainedwithasamplelengthof8.4mmcorrespondingtoavolumeof80µl.Withahigherpoweramplifier,weshouldbeabletoreach110kHzbasedonbenchmeasurements.13CB1fieldsof>71kHzhomogeneity(810°/90°)of89%areroutinelyobserved.Underfull1Hdecouplingforlongperiodsoftime,sampleheatingduetothehighRFfieldisminimalevenforsamplecontainingphysiologicallevelsofsalt.Thepowerhandlingcharacteristics,B1fields,andhomogeneitiesmakethisanidealprobeforthefullrangeofsolidstateNMRexperiments,includingsequenceswhichuseextendedperiodsofcontinuousRFpulsingonbothchannels.Werecentlypublishedapaperdescribingdesignconsiderationsaswellassomeinitialresults3.Amoredetailedmanuscriptdemonstratingtheprobe’scapabilitieswithavarietyofsamplesandpulsesequencesisnearingcompletion.

rEfErENCES[1]Doty,F.D.,et al.,J.Magn.Reson.182(2006)239-253.[2]Gor’kov,P.L.,et al.,J.Magn.Reson.185(2007)77-93.[3]McNeill,S.A.,Gor’kov,P.L.,Struppe,J.,Brey,W.W.,andLong,J.R.,Magn.Reson.Chem.45(2007)S209–S220.

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This report identifies the components of crude oil that readily dissolve in water (both fresh and saltwater).Thisinformationisimportantintracingthesourceandremediationofoilspillsintheenvironment.Thiscouldbeofgreatimportanceinspillsthatoccurinthewatertable.• This work was published in environmental science & technology (2007).

WHiCH CoMponEnts oF CrudE oil dissolvE in WatEr?Lateefah Stanford (FSU Chemistry & Biochemistry), Sunghwan Kim (Korean Basic Science institute, Korea), Geoffrey C. Klein (FSU Chemistry & Biochemistry), Donald F. Smith (FSU Chemistry & Biochemistry), ryan P. rodgers (NHMFL Tallahassee; FSU Chemistry & Biochemistry), and Alan G. Marshall (NHMFL Tallahassee; FSU Chemistry & Biochemistry)

rESULTS AND DISCUSSIONThefirststepinunderstandingpetroleum crude oil spills isto identify which chemicalcomponents dissolve inwater.Here,weuseultrahigh-resolution magnet-basedmassspectrometrytoresolveand identify, for the firsttime, thousands of differentchemical components ofcrude oil and water exposedto that oil.1 Of the 7,000+acidic species identified inSouth American crude oil,surprisingly many are water-soluble, and many more inpure water than in seawater(see Figure. Top: crudeoil. Bottom: water-solublecomponents).Watersolubilitydepends on molecularweight, size, and heteroatom(nitrogen, oxygen, sulfur) content. Acidic oxygen-containing chemicals are most prevalent in the water-solubles,whereasacidicnitrogen-containingchemicalsareleastsoluble.Incontrast,basicnitrogen-containingchemicalsarewater-soluble.(Peaksnotedwithanasteriskinthedistilledwater-solublebasesportionoftheFigurearenitrogen/oxygen/sulfur-containingcompoundstoodilutetobedetectedintheparentoil.)Possiblestructuresareshownfortwoofthechemicalcomponents.

ACkNOwLEDgEMENTSThisworkwassupportedbytheNSFNationalHigh-FieldFT-ICRMassSpectrometryFacility(DMR06-54118),FloridaStateU.,andNHMFL.

rEfErENCES[1]Stanford,L.A.et al.,Environ.Sci.Technol.41,2696-2702(2007).

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TRY TechniquedevelopmenttoimprovebothFT-ICRmassspectralsignal-to-noiseratio(atfixedresolving

power)andresolvingpower(atfixedsignal-to-noiseratio).Thetime-domainsignaldurationincreasesbyuptoafactorof2ormore.Mechanismisunderinvestigation.• This work was published in analytical chemistry (2007).

ModiFiCation oF trapping potEntial by invErtEd sidEkiCk ElECtrodE voltagE during dEtECtion ExtEnds tiME-doMain signal duration For signiFiCantly EnHanCEd FouriEr tranForM ion CyClotron rEsonanCE Mass rEsolutionSunghwan Kim (Korean Basic Science institute, Korea), Myoung Choul Choi (Korean Basic Science institute, Korea), Seungyoung Kim (Korean Basic Science institute, Korea), Manhoi Hu (Korean Basic Science institute, Korea), Jong Shin Yoo (Korean Basic Science institute, Korea), Hyun Sik Kim (Korean Basic Science institute, Korea), Greg T. Blakney (NHMFL Tallahassee), Christopher L. Hendrickson (NHMFL Tallahassee; FSU Chemistry & Biochemistry), and Alan G. Marshall (NHMFL Tallahassee; FSU Chemistry & Biochemistry)

rESULTS AND DISCUSSIONApplyinganinvertedvoltagetothe“sidekick”electrodesduringioncyclotronresonancedetectionimprovesbothFouriertransformioncyclotronresonance(FT-ICR)massspectralsignal-to-noiseratio(atfixedresolvingpower)andresolvingpower(atfixedsignal-to-noiseratio)1.Thetime-domainsignaldurationincreasesbyuptoafactorof2ormore.Themethodhasbeenappliedto7TFT-ICRMSofelectrosprayedpositiveionsfrom

substanceP(seeFigure)andhumangrowthhormoneprotein(~22,000Da,m/Δm50%≈200,000),withouttheneedforpulsedcoolinggasinsidetheICRtrap.ThemodificationcanbeeasilyadaptedtoanyFT-ICRinstrumentequippedwithsidekickelectrodes.Thepresenteffectsareshowntobecomparabletoelectronfieldmodificationby injectionofanelectronbeamduring ICRdetection, reportedbyKaiserandBruce2. Althoughtheexactmechanismisnotfullyunderstood,computersimulationsshowthataflatteningoftheradialpotentialgradientalongthemagneticfielddirectionandformationofaninvertedlocalpotentialgradientwellintheICRtrapmaycontributetotheeffects.ThisstudyprovidesnotonlyawaytoenhancethequalityofFT-ICRmassspectrabutalsooffersinsightintounderstandingofionmotionsinsideanICRiontrap.

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ACkNOwLEDgEMENTSWethankJohnP.QuinnforhelpininterfacingthePredatordatastationtotheBrukerFT-ICRmassspectrometer.WealsothankDrs.Jung-KeunSuhandYoung-LanJungforprovidingproteinstandardsamples.ThisworkwassupportedbytheNSFNationalHigh-FieldFT-ICRMassSpectrometryFacility(DMR06-54118),FloridaStateU.,NHMFL,andtheKoreanBasicScienceInstitute.

rEfErENCES[1]Kim,S.et al.,Anal.Chem.79,3757-3580(2007).[2]Kaiser,N.K.et al.,Anal.Chem.77,5973-5981(2005).

Thecombinationofspecificionizationtechniquesandaccuratemass,highresolutionFouriertransformioncyclotronmassspectrometrypermittheassignmentofchemicalcompositionandstructurepredictionbasedsolelyuponmass.• This work was published in the Journal of the american society of mass spectrometry (2007).

MolECular struCturE FroM MolECular MassJeremiah M. Purcell (NHMFL Tallahassee; FSU Chemistry & Biochemistry), ryan P. rodgers (NHMFL Tallahassee; FSU Chemistry & Biochemistry), Christopher L. Hendrickson (NHMFL Tallahassee; FSU Chemistry & Biochemistry), and Alan G. Marshall (NHMFL Tallahassee; FSU Chemistry & Biochemistry)

rESULTS AND DISCUSSIONThesmallestchemicallydistinctunitofmatterisamolecule.High-resolutionmassspectrometrycandeterminethechemicalformulaofamolecule:i.e.,itsnumberandtypesofconstituentatoms,e.g.,CcHhNnOoSs.However,massalonecannotusuallydeterminehowtheatomsarelinkedtogetherinthemolecularstructure.NHMFL/FSUresearchershaverecentlyshownthatultrahigh-resolutionFouriertransformioncyclotronresonancemass

spectrometry (FT-ICR MS) can differentiate molecules containing a nitrogen atom in a five-member vs. six-memberaromaticring(asincrudeoil).Atmosphericpressurephotoionizationdistinguishesthetwokindsofringsinasinglepositive-ionmassspectrum(afive-memberringyieldsM+•ions,whereasasix-memberringyields(M+H)+ions)1.HighmagneticfieldFT-ICRMSisrequired,becauseitisnecessarytoresolvemoleculesdifferinginmassbylessthan0.005ofthemassofthesmallestatom(hydrogen)--seeFigure.

ACkNOwLEDgEMENTSThisworkwassupportedbytheNSFNationalHigh-FieldFT-ICRMassSpectrometryFacility(DMR06-54118),FloridaStateU.,andNHMFL.

rEfErENCES[1].Purcell,J.M.et al.,J.Am.Soc.MassSpectrom.18,1265-1273(2007).

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MgB2andtogreatlyrefinethegrainsizeoftheMgB2.Evenafterhotisostaticsinteringat1000°C,itispossibletoobtaingrainsizesof20nmor less.ThestrongscatteringproducedbytheCandfinegrainsizemainlyenhancethepropertiesintheinferiorHparalleltothecaxisdirection,whereitismostusefultoapplications.Theirreversibilityfieldhasthusbeenenhancedfromabout11to17Twhiletheveryfinegrainsalsobenefitfluxpinning,generatingthehighestcriticalcurrentdensitiesyetreportedinbulkMgB2.• This work was published in superconductivity science and technology (2008). Another paper published on this work in 2007, “Understanding the route to high critical current density in mechanically alloyed Mg(B1-xCx)10’ was chosen for inclusion in the ‘Superconductor Science and Technology’ (SuST) 2007 highlights.

iMproving pErForManCE in bulk MagnEsiuM diboridE by iMprovEd proCEssingB.J. Senkowicz, J. Jiang, J. zhou, P.J. Lee, E.E. Hellstrom, and D.C. Larbalestier (FSU-NHMFL Applied Superconductivity Center)

INTrODUCTIONBulkformmagnesiumdiboride(MgB2)isapromisingmaterialfor use in constructing superconducting magnets withoperationtemperaturesupto20K,ormid-fieldmagnets(<10T)operatingat4.2K.Theprocessingconditionsleadingtooptimalpropertiesaretheobjectofmuchinvestigation.In this work, we examined the effects of carbon alloying,highenergyballmilling,andheattreatmenttemperatureonperformance (critical current density) and used our resultsto describe a complex interaction between processingparametersandpropertiesfocusingonelectronscattering,grainsize,latticecomposition,andelectricalconnectivity.

ExPErIMENTALThree sample sets (pellets) were synthesized with varyingcarbon content by a process involving mechanical alloying (in high energy ball mill) of pre-reacted MgB2powderwithgraphitepowder(dopant),followedbyhotisostaticpressing.SetAwasunmilledandundoped.SetBwasmilledandundoped.SetCwasbothmilledanddoped.OnesamplefromeachsetwasHIPtreatedat900°C,950°C,1000°C,1150°C,and1500°C.Thesinteredpelletsweresectionedwithadiamondsaw,andtheirpropertiesinvestigated.Thisexperimentusedthefabrication,characterization,andmicroscopyfacilitieslocatedattheAppliedSuperconductivityCenter,aswellasthe33TresistivemagnetintheDCfielduserfacility.

rESULTS AND DISCUSSIONWefoundthatJc(H,T)benefitedstronglyfromfinegrainsizes<50nm,availablebyheattreatingat950°CorlowerT.However,sinteringwaslimitedbelow1000°CcausingJctobelimitedbyelectricalconnectivity.InthisworkwefoundthathighenergyballmillingreducedtheTnecessarytoachieve~50%offullconnectivityfrom>950°Cto~900°Cinundopedsamples.Thisadvanceenabledsuccessfulheattreatmentat900°C,resultinginanunprecedentedcombinationofconnectivityandfinegrainsFigure1.Whenbeneficialcarbonwasaddedtothematerial,wewereabletoachieveextremelyhighJc(8T,4.2K)>5x104A/cm².Furtherinvestigationrevealedthatthebenefitsoffinegrainsizearenotlimitedtofluxpinningimprovement,buttochangesintheelectronscatteringstateofthematerialwhichresultinimprovementofthecriticallyimportantperformance-limitingHc2(H//c-axis)withnosignificantchangetoHc2(H//ab-plane).

CONCLUSIONSThis work simultaneously explored several processing variables and resolved their interrelated effects,resulting in excellent material performance and the knowledge necessary to tailor performance to thetemperature and magnetic fields of applications by manipulating heat treatment schedules, mechano-chemicalprocessing,andcomposition.

ACkNOwLEDgEMENTSThisworkwasfinanciallysupportedbytheUSDepartmentofEnergythroughtheDivisionofHighEnergyPhysics(DE-FG02-07ER41451)andOfficeofFusionEnergyScience(DE-FG02-06ER54881)andalsoourNSFfocusedresearchgroupDMR-0514592.

rEfErENCES[1] Senkowicz,B.J.,et al.,SuperconductorSci.Technol,20,650-657(2007).[2] Senkowicz,B.J.,BJ;Mungall,RJ;Zhu,Y,et al.SuperconductorSci.Technol.21(2008) M

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Figure 1.Critical current density as a function of heat treatment temperature and milling status.

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RoundwireBi-2212coiltechnologyemergedduring2007withaseriesof12coilsinwhichmanyoftheobstaclestoimmediateexploitationofthepromiseofBi-2212wereidentified.Alongthepathtoa7TeslainsertcoilaimedatsurpassingthepreviousBi-2212coilrecordof5Tina20Tbackground,thepotentialofRWBi-2212 isnowestablished.The tendencyof theconductor to leak in thepresenceof theusefulandwidelyusedstructuralceramic(Macor)meansrelianceonmorecomplexinsulations,asdoesthetendencytoreactwithbraidedmulliteinsulations.Identificationoftheseissueshasledtobetterperformancewithall-metalcoilformssuchasInconel600.Extensiveconductorevaluationhasshowntheneedtosharpenthesuperconductingtransitionandtoavoiddegradationoftheconnectivityoftheconductorsbyanystepinthereactionprocess.Thisworklaysoutthekeyissuesformakingthisnewmagnettechnologyviable.

bi2212 ConduCtor and Coil tECHnology For HigH FiEld MagnEtsU.P. Trociewitz, Y. Jiang, E.E. Hellstrom, W.D. Markiewicz, J. Schwartz, and D.C. Larbalestier (Applied Superconductivity Center); S. Hong, Y. Huang, H. Miao, M. Meinesz, B. Czabaj (oxford Superconducting Technology inc., NJ); i.H. Mutlu (Harran Üniversitesi, Turkey)

DevelopmentofBi2Sr2CaCu2O8+x(Bi2212)conductorforhigh-fieldmagnettechnologyapplicationsisafocusattheAppliedSuperconductivityCenter(ASC)1.AdesignofahighfieldinsertmagnetmanufacturedusingBi2212roundwireinawindandreact(W&R)approachhasbeendeveloped.Initscurrentconfigurationthemagnetwilldeliver7Tinabackgroundmagneticfieldof18T.Themagnetdesignconsistsoffoursub-shellswithvaryingamountofexternal reinforcementoneachshellandwillhaveaboresizeof30mm.ThewireisBi2212/Ag-alloy,85x7multifilamentwiremanufacturedbyOxfordSuperconductingTechnology(OST).Ithasatotaldiameterof1.3mmincludinga0.15mmthick3Al2O3-2SiO2mullitefiberbraid2.Tounderstandand

solvepotential issueswiththermo-processingof largerwindingpacksandotherbasic technology issues,aseriesofsmall sample-coilshavebeenwoundonmandrelsmade fromMacor,amachinableglass-ceramic.They were heat-treated and studied regarding superconducting, and microstructural properties, as well asregardingchemicalcompatibilitybetweenconductor,electricalinsulationandstructuralmaterials.Thecoilswereheat-treatedapplyingthetypicalthree-stepheat-treatmentprocessinflowingO2includingpartial-melt,recrystallization,phaseformationandphaserefinerysteps.Incompatibilityissueswereevidentbetweentheconductor,insulationbraidandMacor.WithallcoilswoundonMacormandrelsexcessiveleakagewasfoundthat could only be partially alleviated by changing heat treatment parameters and increase of gas flow, asshowninFigure1.Scanningelectronmicroscopy(SEM)andenergydispersivespectroscopy(EDS) revealedthatMacordecomposesasitreactswiththeconductorreleasingMgandF.ItalsorevealedreactionsbetweentheconductorandtheinsulationbraidcausingerosionoftheAg-alloysheathandtransformationofthemulliteintoabrittleglassthatmayalsoreduceO2diffusion intotheconductorthat isneededtocompleteBi2212M

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Y phase formation.After replacingMacorcoil formswith Inconel600coil forms leakagealmostdisappeared,asseeninFigure2.Thisindicatesthatchemicalreactionsplayamuchstrongerroleinthecauseofconductorleakagethanotherpotentialreasonsthathavebeensuggestedpreviouslylikepre-existingdefects,pin-holes,orinternalpressurebuildupcausedbytheformationofCO2insideoftheconductor.ComparisonoftransportdataofshortsamplesandcoilsshowthatthoughtheconductorsuffersfromconnectivityissuesitispossibletomanufactureW&Rcoilswithdecentperformance.Toincreasepackingdensityandhencetheengineeringcriticalcurrentdensity,alternativestothemullitebraidinsulationarebeingconsidered.Sol-gelcoatingwithZrO2hasshownpromisingresultsinshortsamplesandneedstobeevaluatedfurther.

rEfErENCES[1]Weijers,H.W.,Trociewitz,U.P.,Marken,K.,Meinesz,M.,Miao,H.,Schwartz,J.,Supercond.Sci.Technol.17(2004)636-644.[2]MiaoH,MarkenKR,MeineszM,CzabajB,HongS,TwinA,NoonanP,TrociewitzUP,SchwartzJ,IEEE Trans. Appl. Supercond.17(2)

(2007)2262–2265.

Worktowardaconicalborehighfieldmagnetsuitableforneutronscatteringexperimentsmadeasignificantadvancewiththetestoftheconicalmodelcoil.HereisanexampleofthefurtherdevelopmentofacoretechnologyoftheNHMFLallowingresistivemagnetsinnewcoilconfigurations,extendingtherangeofmagnetapplications.TheobjectiveistosupplyaconicalmagnettotheSpallationNeutronsource(SNS)andtherebyusetheexpertiseoftheNHMFLtomeetcriticalinstrumentationrequirementsofcollaboratinginstitutions.

tHE dEsign and tEst oF tHE ConiCal ModEl CoilJ. Chen, M.D. Bird, J. Toth, J.W. o’reilly, S. Bole, Y. L. Viouchkov (FSU, NHMFL MS&T)

INTrODUCTIONIntheautumnof2006agrantwasawardedbytheNSFforaConceptual and Engineering Design (CED) of conical borehybrid magnet suitable for neutron scattering experimentsattheSpallationNeutronSource(SNS) inOakRidge,TN.TheConicalFlorida-Bitter(CFB)technology(pat.pend.)isthenoveltechnology enabling for the design of this magnet.We havebuilt a CFB model coil that has been tested to high current-density,powerdensity,stressandfieldattheMagLab.

ThE DESIgN Of ThE CONICAL MODEL COIL The basic design requirements include: 32mm bore, 15° halfangle,5mmsamplediameteranddcpowerlessthan8MW.Thedisksofa30TmagnetAcoilareusedtobuildthemodelcoil.TheuniquefeatureinCFBtechnologyisthattheinnerradiiofthedisksindifferentzonesaredifferent,asshowninFigure1.Thereforethedistributionofthecurrentdensity,temperatureand stresses are different for each zone and need to becalculatedzonebyzone.Themaindesignparametersandthedetailedzoneparametersarelistedinreference1.

ExPErIMENTALThe conical model coil was installed in the housing, whichwasespeciallydesignedforthetestingofvariedcoils,andthewholeassemblywasinsertedintheexisting20-T200-mmboreresistivemagnet(largeboreincell4).Fourdifferenttestswerecarried out, including high power testing (insert only), highstresstesting(insert+outsert),cyclictestinganddestructivetesting.Watertemperatureatthreedifferentpositions(closetozone2,zone9andcoilouterradiusrespectively)wasmeasuredinordertoevaluatecoolingperformance.

rESULTS AND DISCUSSIONIngeneral,themodelcoilworkedverywell.Itgenerated11.5Tat15kAand14.1Tat18kAcurrent.Thepowerconsumedwasveryclosetothedesignvalue,implyingthatthecoolingeffectsystemperformedasintended. M

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Figure 1.Bi2212 coils on Macor coil forms heat treated with a) 0.5 l/min, and b) with 1 l/min O2 gas flow.

Figure 2.Bi2212 coils wound on Inconel 600 coil forms and in- field transport data.

Figure 1.Section of Conical Florida-Bitter model coil

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Whiledesignedfor15kA,thecoilworkedat18kAcurrent.Inaddition,theclampingforceonthecoilprovedtobelargeenoughtohandletheelectro-magnetictorque.Thewholestructurewasverystable.

CONCLUSIONSThedesignoftheconicalmodelcoiliscomplete.ItwasreviewedbyaninternationalcommitteeinNovember2007.ThemodelcoilwastestedinDec.20,2007.Itgenerated14.1Tinabackgroundfieldof19.4Tforatotalof33.5T.TheCFBtechnology,therefore,isprovedtobesuitableforthehigh-fieldneutronandphotonscatteringexperiments.Itwillenablesuchexperimentsathigherfieldsthanpresentlyavailable.

rEfErENCES[1]Bird,M.D.,et al.submittedtoIEEEappliedsuperconductor,2007

Anessentialstepforwardforultra-highfieldNMRorMRI isthedevelopmentof instrumentationthatallows for the optimization of magnetic field homogeneity in high-field resistive and hybrid magnets.The challenge is to develop shims that can be adjusted to provide corrections throughout a large rangeofavailablebackgroundfieldenablingscientificusers tostudy thefielddependenceofvariousscientificphenomenasuchasnuclearmagneticrelaxation.Withthegoalinmindofobtainingatargetof1x10-6fieldhomogeneityinthefuture36TSeries-ConnectedHybridmagnetsystem,MagLabscientistshavedevelopedanovelshimmingtechniquethatlocatesresistiveshimsontheinnerboreoftheresistivemagnettoallowcoolingoftheshimsfromthepre-existingresistive-magnetcoolingwatersupply.Acompleteworkingshimsethasbeenbuiltandwillbeinstalledinthe25TKeckMagnetin2008.The25TKeckMagnetwillserveasastagingareaforthedevelopmentofshimstobeusedinthe36TSeries-ConnectedHybrid.• This work has been accepted for publication in ieee transactions of applied superconductivity.

rEsistivE sHiMs For HigH-FiEld rEsistivE and Hybrid MagnEtsT. A. Painter, M. D. Bird, S. T. Bole, A. J. Trowell, K. K. Shetty, W. W. Brey (NHMFL), Jingping Chen

INTrODUCTIONTheNationalHighMagneticFieldLaboratory(NHMFL)hasbeenfundedbytheNationalScienceFoundationto construct a Series-ConnectedHybrid (SCH) magnet systemoperated with a single 12 MWpower supply which will produce36teslasand10-6fieldhomogeneityandstabilityovera1cmdiameterspherical volume1. The NHMFLpresently operates a 25T resistivemagnet, referred to as the Keckmagnet,whichemploysferroshimsthat correct the field homogneityto1.2x10-5at25Tovera1cmDSV2.ThetargetedSCHspecificationwillextend the present boundary ofthe high-field, high-homogeneityexperimental environment to10-6homogeneityat36T.Asafirstdemonstration, a new shimmingtechnique will be installed and operated in the Keck magnet to improve its homogeneity from 10-5 usingferroshims (10-4 unshimmed) to 10-6 at 25 T. Resistive shims have been selected for the SCH due to theiroperationalflexibility.Unlikeferroshims,resistiveshimscanbeadjustedtoprovidecorrectionsthroughouttherangeofavailablebackgroundfieldenablingscientificuserstostudythefielddependenceofvariousscientificphenomenasuchasnuclearmagneticrelaxation.Theresistiveshimscanalsobeadjustedasneededtooptimizethefieldcorrectionasresistivemagnetcoilsarereplacedoverthesystemlifetime.M

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Y NOVEL ShIMMINg TEChNIqUEAnovelshimmingtechnique(patentapplicationno.60/854654)isproposedfortheSCHthatlocatesresistiveshimsontheinnerboreoftheresistivemagnettoallowcoolingoftheshimsfromthepre-existingresistive-magnetcoolingwatersupply.Thenoveltechniqueemployssingle-turnscapableofcarrying150Aasopposedto,forexample,150turnsat1amptominimizetheelectricalinsulationthatimpedescoolingfromthewaterchannel.ThetraditionalconductorlocationsandcircuitsforthetransverseshimshavebeenmodifiedtoallowasingleconductorinanovelcircuitryforboththeXandZX(andYandZY)terms.Themodifiedtransverseshimcircuitsincombinationwiththeoptimizedconductoraxiallocationresultedineliminationofanylengthwiseoverlapandtheassociatedincreaseinthermalimpedance.Inaddition,aZ0coilisfabricatedintotheshimsetaspartofthesystemtocorrectfortemporalfieldinstabilitiesinthemagneticfield.Theresultantradialbuildoftheshimassemblyislessthan5.0mm–akeyparameterattheinnerboreofahigh-fieldmagnet.Asanimportantdevelopmentalstep,afullyoperationalshimsetwillbeinstalledintheKeckmagnettoallowthesystemtobedemonstratedandcharacterizedbyregularuseroperationbeforebeingemployedintheSCH.

CONCLUSIONSA novel shimming technique has been conceptualized, designed and built (Figure 1) for correcting spatialinhomogeneitiesinsideahigh-fieldresistiveorhybridmagnetsystem.Theshimmingtechniqueusesresistiveconductorslocatedontheboretubeoftheresistivemagnetwhere(a)theycanbecooledbyapre-existingflowofwaterrequiredfortheresistivemagnetand(b)theyrequireseveralordersofmagnitudelessampereturnsthansuperconductingshimstraditionally locatedontheouterdiameterofthesuperconductingmagnet.Anovelshimcircuitryhasbeenemployedwhichallowsthetransverseshimtermstobedividedandrecombinedtoallowaminimumofturns.Acompleteworkingshimsetwithsixtermshasbeenbuiltandwillbeinstalledinthe25TKeckMagnetattheNHMFLinearly2008todemonstratethefeasibilityofthistechniquetomeetthetargetedobjectiveoftheSCHof1x10-6homogeneityina36Tcentralfieldregion.

ACkNOwLEDgEMENTSManythankstoRainerMeinkeandGerryStelzeratAdvancedMagnetLab,Inc.,Melbourne,FL(www.magnetlab.com)fortheinvaluablecontributionsregardingthefabricationprocessesforthisresistiveshimmingtechnique.

rEfErENCES[1]Miller,J.R.,et al., IEEE Trans. Appl. Supercond.,14(2),1283-1286(2004).[2]Bird,M.,et al., IEEE Trans. Appl. Supercond., 12(1),447-451(2002).

AngulardependentresistivitymeasurementsifYBa2Cu¬3O7(YBCO)films,inpulsedmagneticfields(H)upto50T,havesettlealong-standingdebateonthepresenceofasmecticphasein“loweranisotropy”highTcsuperconductors.WhenHisalignedwiththeCu-Olayers,therapidincreaseofthevortexmeltinglineatlowtemperaturestogetherwiththecriticalexponentvalues,confirmthepresenceofaliquid-smectictransition.Also,upto50T,correlateddefectsstronglyreducethemotionofvorticeswellintotheliquidphase.• This work was published in Physical Review Letters (2008) and was supported by the Magnet Lab’s User Collaboration Grants Program

angular dEpEndEnCE oF tHE MElting linE oF yba2Cu3o7+bazro3 tHin FilMsS. A. Baily, B. Maiorov (NHMFL/STC, LANL); F. F. Balakirev, M. Jaime (NHMFL, LANL); H. zhou, S. r. Foltyn, L. Civale (STC, LANL)

INTrODUCTIONDeep inside the superconducting state when a magnetic field penetrates a superconductor, vortex mattercanexist insolidor liquidphases.Thenatureofthesephases isgivenbythenatureofthepinningcenterspresent.1Pinningcentersmakehightemperaturesuperconductors(HTS)usefulbystabilizingthesolidphaseandenablingfilmstocarrycurrentwithoutdissipation. Whenthemagneticfieldortemperatureincreases,thesolidvortexlatticemeltsandelectricalresistanceincreases.ThemostinterestingcaseoccurswhenfieldisalignedwiththecopperoxideplanesofHTSandmanytypesofpinningcentersarepresent.

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Figure 1.The Keck Shims were produced by Advanced Magnet Lab to demonstrate and characterize performance and operation in a 25 T resistive magnet before integrating into the NHMFL SCH.

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ExPErIMENTALElectrical ac-transport was used to measurethe vortex dissipation in the liquid phase aswell as to determine the melting line (wheredissipationgoestozero),asafunctionofangleforYBa2Cu3O7 (YBCO) films in the 50 T short-pulse magnet using the newly rebuilt rotatorprobe.Theeffectofnaturallygrowndefectsonthemeltinglinewasstudied.

rESULTS AND DISCUSSIONWe find that near 80 K (H>40T), when themagnetic field is aligned with the layers, themelting line turns upward and the criticalexponent that describes the rise in resistivityuponenteringtheliquidstatebecomessimilarto that of a liquid crystal melting transitionas predicted for layered superconductors.2Also, we observe that up to the highest fieldmeasured (50T) correlated defects arrest themotion of vortices well into the liquid phase.At intermediate angles, the complete vortexdissipation can be scaled using the massanisotropymodel.

CONCLUSIONAlong-standingdebateabouttheexistenceofasmecticvortexphasein“lowanisotropy”HTShas been settled, with evidence for a smecticvortexphaseinoptimallydopedYBCOatfieldshigherthan40T.3

ACkNOwLEDgEMENTSThisworkwassupportedbytheNSFthroughtheNHMFLandNHMFLUCGP,theStateofFloridaandtheDOE.

rEfErENCES[1]G.Blatter,et al.,Rev.Mod.Phys.66,1125(1994).

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usingYBCOtapes isprovingveryattractiveforapplications.Thiemeet al.presentdataontapesmadebytheAMSCRaBITStechniqueinaformusefulforveryhighfieldsolenoiduse.Currentdensitiesofalmost500A/mm2at25Tmakeitclearthatthesematerialsaregoingtobeveryattractiveforhighfieldsolenoids.

HigH FiEld stability Exploration oF sECond gEnEration Hts C.L.H. Thieme, K. Gagnon, (American Superconductor - AMSC), Honghai Song, J. Schwartz (NHMFL/FSU)

INTrODUCTION2GHTSwire isbasedonhighperformancethinfilmYBCOsuperconductor.AMSCusesabi-axiallytexturedsubstratewithathinepitaxialoxidebufferlayer(RABiTSTM).TheYBCOlayerisgrownusingasolution-basedcoating process carried out on a 4 cm wide web. After completion of all coatings the conductor is slit tomultiple4mmwidths.Theseare laminatedonbothsides toa4.4mmcopper foil1, resulting inaso-called344superconductor.Foracapplicationsastainlesslaminatecanbeselected2.Icimprovementsareobtainedthroughimprovedchemistryandreactorconditions3.

ThemainobjectiveofthisSTTRProjectistheexplorationofthesuitabilityofSecondGenerationHTSforhighheatload,highradiationenvironmentapplications.ThePhaseIaimedatanextensivecharacterizationofJe(B,T,)(whereistheanglebetweenthefieldandsurfaceoftheconductor)andestablishingthethermallimitinvariousstabilityexperimentsusingsmallcoils.Theoperatingregimeofinterestislowtemperatures(4.2-27K)andfieldsupto25T.PreviousmeasurementsattheNHMFLdemonstratedanengineeringcriticalcurrentof225A/mm2at25T,parallelfield.Wecharacterizedshortlengthsofanew,thickerfilmconductorat4.2Kandfieldsbetween3and25T.Wethencontinuedwiththecharacterizationofmultiple10mlengths.Thesewereusedtobuildvariousinstrumentalpancakecoils,seeFigure1,intendedforstabilitymeasurementat4.2kandfieldsof6-7T.

ExPErIMENTALThe 344 superconductor for this STTR Project was madeusingaso-calleddoublelayergeometry,resultingina1.4m thickYBCO layer with different pinning characteristicsfortopandbottomlayer.The4.4x0.2mmconductor(0.88mm2area)has50%copperstabilizer.Theconductorshowedacriticalcurrentexceeding100Aat77K,SF.Lengthsofthisconductorwereusedformeasurementsathighmagneticfield, with field orientations parallel and perpendicular tothe face of the tape-like conductor. In parallel fields theconductorwasmeasuredusinganadaptedITERprobe.Twopairofvoltagetapswereplacedat40and60cmdistance,with a minimum distance of 15-20 cm between currentleadsandoutervoltagetaps.Thesamplewasalwaysundercompression.This worked well except for very high fields(24-25T)whentheconductorcouldbuckle.

rESULTS AND DISCUSSIONInparallelfieldstheIcreductionwithfieldwasgradual,asanticipatedfromearlierwork.At10,15,20and25teslathecriticalcurrentwas643,557,486and418A(or1600,1390,1215and1045A/cm-width),resultinginanoverallcriticalcurrentJe(includingcopperstabilizer)of670,580,506,and435A/mm2.Thesevaluesareroughlyproportionaltothelayerthicknesscomparedtoearliervaluesin0.8mthickYBCOfilms.Inaperpendicularfieldthecriticalcurrentsweremuchlower,againasexpectedbasedonearliermeasurements,withJevaluesof208(5T),133(10T),101(15T),83(20T)and73A/mm2(25T).Thesevaluestoowereinlinewithwhatcouldbeexpectedfortheincreasedfilmthickness.

CONCLUSIONSThehighdemonstratedengineeringcriticalcurrents(475A/mm2at25T)areofinterestforthosehighfieldapplicationsinwhichtheHTSmagnetsectionisplacedinabackgroundfieldwithfieldparalleltotheconductor.Themeasurementsarethefirstandagoodstartinaseriesforafullcharacterization,beforesmallpancakecoilsmadeofthesameconductorwillbetestedforstabilityinamagneticfield. M

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Figure 1.Epoxy impregnated pancake coil made of YBCO coated conductor. The coil is heavily instrumented for upcoming stability testing.

Figure 1.Top: Normalized resistance vs. scaled field at two temperatures. Bottom: e())H vs. Temperature with the H applied at different orientations

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ACkNOwLEDgEMENTSThisSTTRProgramissupportedbytheU.S.DepartmentofEnergy,OfficeofHighEnergyPhysics.

rEfErENCES[1]M.WRupich,U.Schoop,D.T.Verebelyi,C.L.H.Thieme,X.Li,W.Zhang,T.Kodenkandath,Y.Huang,E.Siegal,D.Buczek,W.Carter,N.

Nguyen,S.Fleshler,J.Lynch,R.Harnois,”DevelopmentofSecondGenerationHTSWireatAmericanSuperconductor”,IEEETrans.onAppl.Supercond.17,3379(2007).

[2]LiXetal,2007IEEETrans.onAppl.Supercond.17,3553(2007).[3]C.L.H.Thieme,K.Gagnon,J.Voccio,D.Aized,andJ.Claassen,”ACapplicationofSecondGenerationHTSwire”,JPhysics:Conf.ser.

(JPCS),EuropeanConferenceonAppliedSuperconductivity,September2007,Brussels.

Controllingfusionenergy,thesourcethatdrivesthesun,istheobjectiveofITER,theInternationalThermonuclearExperimentalReactor.TheNHMFLprovidesuniquefacilitiesforthetestingofNb3SnsuperconductorintendedforuseintheITERmachine.Inearlierwork,theverylargedegradationofcriticalcurrentwithbendingstraininadvancedhighcurrentdensityinternaltinprocessconductorswasrevealed.Thesemeasurementsaremadeonsinglestrandsinpurebending,andarethereforeafundamentalaspectoftheperformanceofcablesundermorecomplexloadpatterns.Intherecentworkreportedhereofanexpandedstudy,thelargedegradationassociatedwithhighcurrentdensityinternaltinwiresisconfirmed,andcomparedwiththemuchlowerdegradationcharacteristicofconventionalbronzeprocesswires.Acleartradeoffbetweenavailablecurrentdensityandstrainsensitivityisshown.ThesemeasurementsareessentialinprovidingtheinformationnecessarytomakedesignselectionsfortheITERconductors.

bEnding EFFECt on nb3sn supErConduCting WirEsMakoto Takayasu, Luisa Chiesa, Joel H. Schultz, Joseph V. Minervini (Massachusetts institute of Technology, Plasma Science and Fusion Center), and John r. Miller (oak ridge National Laboratory)

INTrODUCTIONBendingeffectsonNb3SnwireshavebeeninvestigatedtounderstandthecriticalcurrentdegradationoflargeNb3Snsuperconductingcables,suchastheITERconductors.Avariable-bendingdevicehasbeenconstructedforcharacterizingthecriticalcurrentsofNb3Snsuperconductingstrandunderpurebendingwithoutunaxialtensionorcompression.Thisdevicehasbeensuccessfullydeveloped1andhasbeenusedtotestseveralNb3Snwires:ITERTFUSwiresofLuvataandOxfordinternal-tinwires,andotherITERrelatedNb3Snwires(EuropeanEASbronzeandEM-LMIinternaltin,andJapaneseFurukawabronzewires).

ExPErIMENTALPure bending experiments for various Nb3Sn wires were performedwithourpure-bendingdeviceusingthe20T,195mmBittermagnetat NHMFL. Our bending test device allowed applying pure bendingstrainstoastrandduringtestoperationinliquidhelium1.ThestrandsampleswereplacedonasupportbeamplatemadeofTi-6Al-4Vthatwasdeformedthroughaseriesofpurebendingstates.Thisdevicecanapplya large rangeofbending,upto0.8%of thenominalbendingstrainatthewiresurface.Theactualpeakbendingstrainofthefilamentsin the wires was about 65% of the nominal bending strain values,dependingoncopper/noncopper fraction.Thecriticalcurrentsweremeasuredatevery0.1%incrementofbendingupto0.8%.Irreversibledegradationofthecriticalcurrentduetobendingwasmeasuredbyreleasingbendingaftereach0.1%increment.

rESULTS AND DISCUSSIONWetestedfivedifferentNb3Snwireswhichweredevelopedbythe ITERparties.Threewere internal-tinwiresofrecentlydevelopedITERTFUSOxfordandLuvatawiresandEUEM-LMIwire.TwoofthemwerebronzewiresofEUEASandJapaneseFurukawadesigns.Thecriticalcurrentsdegradedwithincreasingthebendingstrains.At0.8%nominalbendingstrainsthecriticalcurrentsoftheinternaltinwiresweredegradedby47%forOxfordwire,40%forLuvatawireand30%forEM-LMIwires.HighercurrentdensitywiresuchastheOxfordwireseemstodegrademorethanlowercurrentdensitywires.Ontheotherhandwiththesame0.8%nominalbending,bronzewiresmadebyFurukawaandEASbothdegradedbyonly10%.After0.8%bending,OxfordandLuvatawiresshowed13%and1.3%irreversiblepermanentdegradationoftheirinitialcriticalcurrentvalues,respectively.ItisnotedthatsomewiressuchastheFurukawawireshowsmallimprovementsofthecriticalcurrentswithappliedbendinguptoabout0.3%.M

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rEfErENCES[1]D.L.Harris,et al., “PurebendingstrandtestofhighperformanceNb3Snwires,”Adv.Cryo.Eng.,54,Plenum,N.Y.,341-348,(2008).

HalleffectmeasurementsinYBCOat12%dopinghavebeenextendedtohighBupto45T.ItisfoundthattheHallcoefficientRHispositiveathightemperatures,butbecomesstronglynegativebelow~70K(TC=67.5K).ThisisbelievedtorevealthepresenceofelectronpocketsintheFermisurface,whichwouldthengiverisetothepreviouslyobservedquantumoscillationsatlowtemperatures.ItisproposedthatelectronpocketsarisefromareconstructionoftheFermisurface,butthemechanismremainsunidentified.• This work was published in Nature (2007).

nEgativE Hall CoEFFiCiEnt in tHE norMal statE oF HolE-dopEd CupratE supErConduCtorsN. Doiron-Leyraud, D. LeBoeuf, J.-B. Bonnemaison, L. Taillefer (Sherbrooke); C. Proust (LNCMP); r. Liang, D. Bonn, W. Hardy (UBC); L. Balicas (NHMFL)

INTrODUCTIONEarlier thisyear,quantumoscillations in theHall resistanceof thecuprate superconductor YBa2Cu3Oy (YBCO) at 10% doping wereobserved1, convincingly showing that there is a Fermi surface inunderdopedcuprates.Yet,thelargemagnitudeandnegativesignoftheHallresistanceremainedapuzzlingissuegiventhatYBCOisahole-dopedmaterial.Tounderstandthisproblem,wecarriedoutfurtherhigh-fieldmeasurementsoftheHallresistanceofYBCO.

ExPErIMENTALTheHallandlongitudinalresistancesweremeasuredusinga4-pointlock-inmethod.Thesamples,grownatUBC,weredetwinnedchain-orderedYBCOplateletswithdopingsof10and12%.Measurementsweredoneinthe45ThybridmagnetinTallahasseeduringtheweekofMarch26-30,2007.Thecurrentwaslongthea-axisandthemagneticfieldalongthec-axis.

rESULTS AND DISCUSSIONInthefigureontherightweshowtheHallcoefficientRHmeasuredinYBCOat12%dopingasafunctionofmagneticfieldupto45T.WeseethatRHispositiveabove70K,andstronglynegativebelow.Strikingly,at70KRHvanishesatallfields,showingthatthesignchangeisfieldindependentandoccursabovethesuperconductingTC of 67.5 K.While previous studies on cuprates (see, e.g.,2) limited to low field below 25T attributed thissignchangetoanegativefluxflowcontribution,ourhighfielddatademonstratethatanegativeRHat lowtemperature is an intrinsic normal-state property.These results, obtained at the NHMFL, were published inNatureon22November2007.3

CONCLUSIONSInordertounderstandthepronouncedtemperaturedependenceandsignchangeofRH,onemustinvokeascenariowheretwotypesofcarriers-electronsandholes–withdifferentmobilitiesarepresent.BecausethequantumoscillationsareobservedatlowtemperaturewhenRHisnegative,weconcludethattheycomefromsmallelectronpocketsintheFermisurfaceofYBCO.ThisobservationcanbeexplainedbyareconstructionofthelargecylindricalholeFermisurfaceintosmallholeandelectronpockets3,asisbelievedtooccurinelectron-dopedcupratesbecauseofantiferromagneticordering.ThenatureoftheordercausingthereconstructioninYBCOremainstobeidentified.

ACkNOwLEDgEMENTSWeacknowledgesupportfromtheCanadianInstituteforAdvancedResearch,theNHMFL,andfundingfromtheNSERC,theFQRNT,aCanadaResearchChair,theNSF,andtheStateofFlorida.

rEfErENCES[1]Doiron-Leyraud,N.et al.,Nature447,565(2007). [3]LeBoeuf,D.,et al.,Nature450,533(2007).[2]Harris,J.M. et al.,Phys.Rev.Lett.71,1455(1993).

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DeviationfromstandardFermi-liquidbehavior isobservedintheparamagneticstateofNaxCoO2atx=0.75,andasaresultoftheinterplaybetweenitinerancyandlocalizedS=1/2momentsonatriangularsuperlattice.Theupturninthelowtemperaturespecificheatandtheanomalousscatteringintheresistivitybothpoint to theexistenceofanovelkindof lowenergyexcitation.That theseexcitationsappear tobesuppressedbyamagneticfieldsuggeststhatthesearespinfluctuations.Onesuggestionisthatthelocalmomentsformaspinliquidstatewhichco-existswithitinerantelectrons.• This work is published in Physical review Letters and was supported by the Magnet Lab’s user collaboration Grants Program.

loCal MoMEnt, itinEranCy and dEviation FroM FErMi liquid bEHavior in naxCoo2 For 0.71 • x 0.84L. Balicas (NHMFL); Y. J. Jo (NHMFL); G. J. Shu (National Taiwan University); F. C. Chou (National Taiwan University); P. A. Lee (Physics-MiT)

INTrODUCTIONWe report the observation of Fermi surface (FS) pockets via theShubnikov de Haas (SdH) effect in NaxCoO2 for x = 0.71 and 0.84,respectively1.OurobservationsindicatethattheFSexpectedforeachcompoundintersectstheircorrespondingBrillouinzones,asdefinedbythepreviouslyreportedsuperlatticestructures1, leadingtosmallreconstructed FS pockets,but only if a precisenumber of holes per unitcellislocalized.For0.71•x < 0.75 the coexistenceof itinerant carriers andlocalized S = 1/2 spins ona paramagnetic triangularsuperlattice leads at lowtemperatures to theobservationofadeviationfromstandardFermi-liquidbehavior in the electricaltransportandheatcapacityproperties, suggesting theformation of some kindof quantum spin-liquidgroundstate.

ExPErIMENTALWe performed electricaltransportmeasurementsinNa0.71CoO2 and Na0.84CoO2using the hybrid magnetin conjunction with a 3Herefrigerator and a rotatingsampleholderinordertodetectShubnikovdeHaasoscillations.Resultsforx=0.71areshowninFigure1.WhileHeatcapacityandresistivitymeasurementsatlowfieldswereperformedbyusingaPPMS(Figure2).

rESULTS AND DISCUSSIONTheSdHoscillationscanonlybeunderstoodbytheintersectionoftheoriginalFermisurfaceofthesematerialswiththesuperlatticeinducedBrillouinzone,ifforbothconcentrationsatleastoneholepersuperlatticeunitcellislocalized.Thusforx=0.71onehas2.5itinerantholescoexistingwithalocalizedmomentpereach12cobaltswithinthesuperlatticeunitcelland1itinerantholesandonelocalizedmomentper13cobaltswithinthesuperlatticeunitcell.

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Insummary,deviationfromstandardFermi-liquidbehaviorisobservedintheparamagneticstateofNaxCoO2asx=0.75,andasaresultoftheinterplaybetweenitinerancyandlocalizedS=1/2momentsonatriangularsuperlattice.Theupturninthelowtemperaturespecificheatandtheanomalousscatteringintheresistivitybothpointtotheexistenceofanovelkindoflowenergyexcitations.Thattheseexcitationsappeartobesuppressedbyamagneticfieldsuggeststhatthesearespinfluctuations.Onesuggestion1isthatthelocalmomentsformaspinliquidstatewhichco-existswithitinerantelectrons.Whileourdatadoesnotallowustodrawanyfirmconclusionontheoriginoftheanomalousbehavior, it isclearthatthecobaltatesofferanewwindowintopossiblenovelgroundstatesinasystemwithcoupledlocalmomentsanditinerancy.

ACkNOwLEDgEMENTSLBacknowledgessupportfromtheNHMFLin-houseresearchprogram,andYJJfromtheSchullerfellowprogram.

rEfErENCES[1]Localmoment,itinerancyanddeviationfromFermiliquidbehaviorinNaxCoO2for0.71£x£0.84L.Balicas,Y.J.Jo,G.J.Shu,F.C.

Chou,andP.A.Lee,Phys.Rev.Lett100,126405(2008).

[2]WoeiWuPai,et al,Phys.Rev.Lett.100,206404(2008).

The properties of graphene, a single atomic sheet of graphite, are currently a subject of intenseresearch.Muchoftheinterestinthistrulytwo-dimensional(2D)systemstemsfromitsunusual,linearlow-energydispersionrelation,wherethelow-energyelectronicexcitationsaredescribedintermsofmassless,chiral, Dirac fermions.This particular dispersion is thus expected to give rise to many properties that aredifferentfromthoseexhibitedbyother2Dsystems.ThereportbyZ.Jianget al.describesseveralinterestingphenomena that are observed when graphene is subjected to high magnetic fields. They include theobservationoftheintegerquantumHall(QH)effectatroomtemperatureandofthenewQHphasesatlowtemperatures.Furthermore,acyclotronresonance(CR)studyofbothsingleandbilayergraphenerevealsseveraldeparturesfromtheconventionalCRon2Dsemiconductorheterostructures.SomeofthedifferencesareattributedtotheinteractionsbetweenDiracquasiparticles.• This research has been published in Science 315, 1379 (2007), and Physical Review Letters: 98, 197403 (2007); 99, 106802 (2007); 100, 087403 (2008).

landau lEvEl spECtrosCopy oF grapHEnEz. Jiang (Columbia University & NHMFL); E.A. Henriksen (Columbia University); K.i. Bolotin (Columbia University); Y. zhang (Columbia University); L.-C. Tung (NHMFL); M.E. Schwartz (Columbia University); M. Takita (Barnard College); M.Y. Han (Columbia University); Y.-J. Wang (NHMFL); G.S. Boebinger (NHMFL); P. Kim (Columbia University), and H.L. Stormer (Columbia University & Bell Labs)

INTrODUCTIONGraphene,asingleatomicsheetofgraphite,isamonolayerofcarbonatomsarrangedinahexagonallattice.Theuniqueelectronicbandstructureofgrapheneexhibitsanunusuallinear low-energydispersionrelation,quitedifferentfromtheparabolicbandscommontoallprevioustwo-dimensionalsystems.Mostinterestingly,thisdispersionresultsinthechargecarriersthatmimicrelativistic,masslessDiracparticles,leadingtointriguingnewphenomena.Inparticular,averyunusualhalf-integerquantumHalleffectandanon-zeroBerry’sphasehavebeendiscoveredingraphene.

ExPErIMENT AND rESULTSTheQuantumHalleffect(QHE)isoneexampleofaquantumphenomenonthatoccursonatrulymacroscopicscale.ThesignatureofQHEisthequantizationplateausintheHallresistance(Rxy)andavanishingmagnetoresistance(Rxx) inastrongmagneticfield.TheQHE,exclusivetotwo-dimensionalmetals,has ledtotheestablishmentofanewmetrologicalstandard,theresistancequantum,h/e2,thatcontainsonlyfundamentalconstants.Aswithmanyotherquantumphenomena,theobservationoftheQHEusuallyrequires lowtemperatures(thepreviouslyreportedhighesttemperaturewas30K).Ingraphene,however,wehaveobservedawell-definedQHEatroomtemperature(seeFigure1.)owingtotheunusualelectronicbandstructureandtherelativisticnatureofthechargecarriersofgraphene1.Inaddition,wehaveobservednewQHphasesatfillingfactorsv=0,±1,and±4atlowtemperaturesandinhighmagneticfields(seeFigure2.forthev=±1and-4state),arisingfromtheliftingofthespinandsublatticedegeneraciesofgrapheneLandaulevels(LL)2.

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Figure 2.(a) The evolution of the exponent of the resistivity as a function of field H for a Na0.735CoO2 single crystal. (b) Heat capacity normalized by temperature C/T as a function of T for several Na concentrations x in a semi-log scale. Straight line represents a linear fit to the x = 0.735 data over the temperature range 0:35 • T • 7 K. (b) C=T as a function of T for x = 0.735 and for several values of the field H.

Figure 1.(a) Resistance R as a function of field H for a Na0.71CoO2 single crystal at T = 0:6 K. (b) The SdH effect or the oscillatory component of R in (a) as a function of H¡1. (c) Amplitude of the fast Fourier transform normalized by temperature T for several values of T. At least six frequencies are detected: F1 = 125 T, F2 = 400 T, F3 = 475 T, F4 = 725 T, F5 = 800 T, and F6 = 1413 T.

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Thephenomenonofcyclotron resonance(CR) results whenincident infraredradiationisabsorbedby the excitation ofcarriers betweenneighboring LLs,with the absorbedf r e q u e n c i e sc o r r e s p o n d i n gto the LL energyseparation.Sincethe1950s,CRhasbeenafundamental toolfor the investigationofsemiconductorbandstructures,whichgenerallyexhibitresonanceenergiesthatarelinearinthemagneticfield.Recently,wehavemadethefirstmeasurementsofLLtransitionsviainfraredtransmissionmeasurementsinbothsingle(Figure3a,Ref.3)andbilayer(Figure3b,Ref.4)graphenesamples,inmagneticfieldsuptoB=18T.WefindthatbothsystemspresentradicaldeparturesfromtheusualCR,exhibitingLLtransitionenergiesthatarelinearinBforsinglelayergraphene,andthatforbilayersshowashiftfromalinear-in-Bdependenceatlowenergiestolinear-in-Bathigherenergies.InfurtherdeparturesfromtraditionalCR,resonanceenergiesinbothsystemsshowadependenceontheLLindex,whileinsinglelayerswehavealsoobservedinterbandinadditiontointrabandtransitions.DeparturesfromtheexpectedratiosofthetransitionenergiesareinterpretedasindicatingphysicsofinteractingDiracquasiparticles,beyondasimplesingleparticlepicture.

ACkNOwLEDgEMENTS

ThisworkissupportedbytheDOE(DE-AIO2-04ER46133,DE-FG02-05ER46215andDE-FG02-07ER46451),NSF(DMR-03-52738andCHE-0117752),ONR(N000150610138),NYSTAR,theKeckFoundation,andtheMicrosoftProjectQ.

rEfErENCES[1]K.S.Novoselov,et al.,Science315,1379(2007).[2]Z.Jiang,et al.,Phys.Rev.Lett.99,106802(2007).[3]Z.Jiang,et al.,Phys.Rev.Lett.98,197403(2007).[4]E.A.Henriksen,et al.,Phys.Rev.Lett.100,087403(2008).CO

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S ThisdescribesastudyofthethermoelectricresponseofcleanBibeyondthequantumlimittoprobeforhighfieldanomalies.AcceptedbyScience,theauthorsobservednewanomaliesinthefielddependenceoftheNernstcoefficient.Theseanomaliesoccurintheultraquantumlimit.Theyappeartobebeyondtheone-particlepicturethatsuccessfullydescribesthelow-fieldpeaksassociatedwithquantumoscillationsandmayconstitutethefirstdetectedsignaturesofelectronfractionalizationinabulkmetal. This work was published in science (2007) and was supported by the Magnet Lab’s Visiting scientist Program.

nErnst EFFECt in ultraquantuM bisMutHKamran Behnia (ESPCi-France), Luis Balicas (NHFML)

INTrODUCTIONThe aim of this project was to study the thermoelectricresponseofacleanbulkmetalbeyondthequantumlimit.Aprevious study detected giant quantum oscillations of theNernstcoefficientinelementalbismuth1.Thisexperimentwassettoprobeanyfurtheranomalyathigherfields.

ExPErIMENTALWebuiltaminiatureprobetomeasureNernsteffectandusedaHe3refrigeratorinsidearesistivemagnetyielding33T.Thermalconductivity in bismuth is field-independent. Therefore, aconstantheatcurrentyieldedaconstanttemperaturegradientalongthesample.Thesignal-to-noiseratioinourDCvoltagemeasurementwasverysatisfactory.

rESULTS AND DISCUSSIONWe resolved three new anomalies in the field dependenceoftheNernstcoefficientbeyondthequantumlimit (seethefigure).Theseanomaliesoccurintheultraquantumlimit.Theyappeartobebeyondtheone-particlepicturethatsuccessfullydescribes the low-field peaks associated with quantumoscillations.Theymayconstitutethefirstdetectedsignaturesofelectronfractionalizationinabulkmetal.

CONCLUSIONSThe results were published in Science.2We intend to pursuethisinvestigationbystudyingtheNernstresponseofbismuthinthehybridmagnetupto45TnextJanuary.

ACkNOwLEDgEMENTSKBissupportedbyDGA/D4SandANR(ICENETproject)andacknowledgesaNHFML-VSPfellowship.LBissupportedbytheNHMFLin-houseresearchprogram.

rEfErENCES[1] K.Behnia,M.-A.Méasson,Y.Kopelevich,Phys.Rev.Lett.98,166602(2007).[2] K.Behnia,L.Balicas,Y.Kopelevich,Science317,1729(2007)

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Figure. 1.Nernst effect as a function of field below (upper panel) and above (lower panel) the quantum limit. Note the three additional peaks.

Figure 1.Magnetoresistance (Rxx) and Hall resistance (Rxy) as a function of the back gate voltage (Vg) in a magnetic field of B = 45 T at room temperature.

Figure 2 .Rxx vs. Vg in tilted magnetic fields.

Figure 3.(left) LL transitions in single layer graphene. Inset shows normalized transmission for three B fields. Dashed lines are best fit to B. (right) LL transitions among the first nine LLs in bilayer graphene. Dashed lines are fit to B; solid lines are fit to theory based on nearest-neighbor tight-binding approximation.

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AmongthereportsoftheMagnetism&MagneticMaterialscategory,therewereanumberofreportsthat present incremental inputs into further understanding of properties of the specific materials. Twoparticularlyinterestingreportswere:ThereportbyJ.Musfeldtet al.,wherethephasediagramandacmagnetodielectriceffectwerestudiedinthefrustratedKagomelatticeNi2V2O8.• ThisworkwaspublishedinPhysical Review B(2007).Also,theworkofS.Hill,et al.,thatdescribesthenewtechniquetoaddressthespin-dynamicsintheso-calledsingle-moleculemagnet[Mn12O12(CH3COOH)16(H2O)4]2CH3COOH•4H2O.• This work was supported by the Magnet Lab’s user Collaboration grants program and has been accepted by Physical review B.

CHEMiCal tuning oF tHE HigH-EnErgy MagnEto-diElECtriC EFFECt in a FrustratEd kagoME lattiCE MatErialMusfeldt, J.L., rai, r.C., Cao, J., Vergara, L.i., Brown, S. (Tennessee), Kasinathan, D. (Davis), Singh, D.J. (orNL), Lawes, G. (Wayne State), rogado, N., Cava, r.J. (Princeton), and McGill, S. (NHMFL)

INTrODUCTIONMagneticfrustrationandcompetinginteractionsinKagomelatticematerialsgiverisetocomplexmagneticfield- temperaturephasediagrams intheM3V2O8system(M=Ni,Co,Mn). InNi3V2O8, the lowtemperatureincommensuratestatedisplaysbothferromagnetismandafinitepolarization.Onemanifestationofmagneto-electriccouplingisalargestaticmagneto-dielectriccontrast.Sizablemagneto-dielectriceffectscanalsoextendtorelativelyhighenergyincomplexoxidesduetospin-lattice-chargecoupling.Thisworkwasdoneusingacombination of optical spectroscopy, first principles calculations, and energy dependent magneto-opticalmeasurementstoelucidatetheelectronicstructureandtostudythephasediagramofNi3V2O8.ThevariablefieldworkwascarriedoutattheNHMFL.

rESULTS AND DISCUSSIONWerecentlydiscoveredthatsizablemagneto-dielectriccontrastcanextendtorelativelyhighenergyincomplexoxides.Theeffectcanbepositiveornegativedependingontheenergy(Figure1).InNi3V2O8,theintermediategap,localmomentcharacterfavorstheobservedfield-inducedmodificationoflocalstructureandresultinghigh-energydielectriccontrast.Sinceacmagnetodielectriceffectisaspectroscopicratherthancapacitancemeasurement, dead layer contact and “leaky” magneto-resistance issues are avoided. Structure-propertytrendsintheM=Ni,Co,Mnisostructutralseriesareextremelyinteresting.Themagneto-dielectriccontrastistunabledependingonthechemicalidentifyofthetransitionmetalcenter(Figure1),aneffectthatweattributetoacombinationoflatticestiffnessandhybridizationeffects.ComplementaryvibrationalmeasurementsonNi3V2O8singlecrystalsrevealchangesinmagneto-elasticcouplingbetweenthenearlydegeneratemagneticground states and pinpoint the lattice displacements that are important for establishing the state withmagneto-electriccross-coupling.AsofterlatticeintheCoanalogcompoundworkstoreducethehighenergymagneto-dielectriccontrast(becausethelatticerelaxesathightemperaturesanddoesnotcoupletothelowtemperaturemagnetictransitions)andremovetheinterestingmagneto-electricphasefromH-Tphasespace.

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WethanktheU.S.DepartmentofEnergyforsupportofthiswork.

rEfErENCES[1] Rai,R.C.,et al.,Phys.Rev.B,74,235101(2006).[2] Rai,R.C.,et al.,Phys.Rev.B,76,174414(2007).

puMp-probE Epr studiEs oF spin dynaMiCs in singlE-MolECulE MagnEtsJ. Lawrence, S. Hill (UF, Physics); F. Macia, J. Tejada (University of Barcelona, Physics); C. Lampropolous, G. Christou (UF, Chemistry); P. V. Santos (Paul-Drude-institut, Berlin, Germany)

INTrODUCTIONWehavedevelopedanovelexperimental techniquethat integrateshigh frequencysurfaceacousticwaves(SAWs)withhighfrequencyelectronparamagneticresonance(HFEPR)spectroscopy(~300GHz) inordertomeasurespindynamicsonfasttimescalesinsinglemoleculemagnets1.

ExPErIMENTALA single crystal of [Mn12O12(CH3COOH)16(H2O)4] 2CH3COOH•4H2O, hereafter Mn12Ac, was mounted on thesurface of a piezoelectric LiNbO3 substrate containing interdigital transducers (IDTs) for the production ofSAWs.Afterpumpingthesystemoutofequilibrium,bytriggeringmagneticavalancheswithshortSAWpulses,the evolution of the spin population within a fixed energy level is measured using HFEPR spectroscopy incombinationwithfastdataacquisitioninstrumentation. Inadditiontoavalancheignition,theSAWscanbeusedtoperturbthesystembymerelyheatingitwithashortpulse.TheHFEPRissimultaneouslyusedasaprobeofthetimeevolutionofthespinsastheyrelaxbacktoequilibrium.

rESULTS AND DISCUSSION

CONCLUSIONSOurresultsdemonstratehowthisnewtechniquecanbeusedtoobtainenergyresolvedinformationaboutspinrelaxationinsinglemoleculemagnets.Inparticular,wefindthatdynamicsinthestablewellaredominatedbyaphononbottleneckeffect,whereasthedynamicsinthemetastablewellcloselyreflecttheintrinsicspin-latticedrivenmagnetizationdynamics.

ACkNOwLEDgEMENTSThisworkwassupportedbytheNationalScienceFoundation(grantnos.DMR0239481andDMR0414809).

rEfErENCES[1] Macia,F.,et al.,Phys.Rev.B, 77,020403(R)(2008).

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Figure 1. Crystal structure, H-T phase diagram, and high energy magneto-dielectric contrast for Ni3V2O8 compared with that of the Co analog, Refs. 1 and 2. Figure 1.

(left) Double potential well diagram for Mn12Ac illustrating how spins relax during an avalanche. Spins in the right well relax to the ground state by emitting phonons, which result in heating of the system. This heating feeds back into the avalanche by exciting spins in the left well. (right) Evolution of the reflected microwave amplitude during an avalanche triggered via a SAW pulse. In (a), f = 270 GHz, B = 1.1 T & mS = −10 to −9; in (b), f = 237 GHz, B = 0.58 T & mS = −9 to −8; in (c) f = 320 GHz, B = 0.54 T & mS = 10 to 9; and in (d), f = 268 GHz, B = 0.54 T & mS = 9 to 8. In (c) and (d), the red traces correspond to microwave absorption during a SAW pulse after the occurrence of the avalanche.

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The magnetoelectric coupling between a magnetic order and an electric polarization, (a type ofmagnetoelectriccoupling),hasneverbeenobservedbefore inorganicmaterials.Thenecessaryprovisionforthephenomenonisthe lossofthecenterof inversionsymmetry. Inthisreport,theauthorsstudytheorthorhombiccompoundCDC(CuCl2•2(CH3)2SO)intheantiferromagneticstate(TN=0.93K).Thelossoftheinversionsymmetryisoccursatthespin-floptransitioninalowmagneticfieldalongthec-axis.Itisthefirstexampleofcoupledmultiferroticbehaviorinanorganicmaterial.

FiEld-induCEd FErroElECtriCity in an organiC quantuM MagnEtV. S. zapf (NHMFL - LANL), M. Kenzelmann (Paul Scherrer institute, zurich), F. Fabris (NHMFL - LANL), F. Balakirev (NHMFL - LANL), Y. Chen (NiST), C. Broholm (JHU)

INTrODUCTIONMagnetoelectriccouplingisgenerallyrareandhasneverbeenobservedbeforeinanorganicquantummagnet.ThecompoundCDC(CuCl2•2(CH3)2SO)howeverexhibitsthenecessarysymmetryforcertainappliedmagneticfieldsHtoallowanelectricpolarizationPtocoexistwithantiferromagnetic(AFM)order.ThiscompoundcontainschainsofCuS=1/2spins1thatareweaklycoupledviasuperexchangeandexhibitAFMorderbelowTN=0.93K,observedinspecificheatandneutrondiffractionmeasurements2.ForHappliedalongthecrystallographica-andc-axes,theAFMorderissuppressed,mostprobablyduetoacompetitionbetweeninterchaininteractionsandfield-inducedstaggeredfields2.ForHalongtheorthorhombicc-axis,AFMorderissuppressedbyH~4T(seeFigure1).Aspin-floptransitionaboveHsf=0.35Tleadstoamagneticallyorderedstate(AFMB)thatbreaksinversionsymmetryalongtheb-axisfor0.35T<H<4T.

ExPErIMENTALWehavemeasuredthemagnetoelectriccurrentofsinglecrystalsofCDCforH||cwiththepolarizationP||bdownto3Hetemperaturesinthe50TshortpulsemagnetatNHMFL-LANL.Therapidrisetimeofthismagnetwasnecessarytoincreasethesignaltonoiseofthemagnetoelectriccurrentinthissample.

rESULTS AND CONCLUSIONOurmagnetoelectricmeasurements (Figure2) indicate that ferroelectricityoccurs in thesameregionofH-Tspaceas theAFMBphasebetween0.35T<H<4TandbelowT=0.93K.Hysteresis isobserved in thepolarizationdependingonthedirectionoftheprevioustwofieldsweeps.Interestingly,wefindthesameresultswith and without electrically poling the sample.The spin polarization calculated from the magnetoelectriccurrentcloselytracksthemagneticorderparameter.Whilethemagnetically-inducedferroelectricityinCDCisfarfrompracticaltemperaturesandfields,itneverthelessdemonstratesthatthisphenomenoncanoccurinawholenewclassofcompounds.

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ThisworkwassupportedbytheNSF,theDOE,andthestateofFloridathroughtheNHMFLandthroughV.S.Z.’sIHRPgrant.WorkatJHUwassupportedbytheNSFthroughDMR-0086210andDMR-9704257.

rEfErENCES[1]R.D.Willettet al,Inorg.Chim.Act4,447(1970);C.P.Landeeet al,Phys.Rev.B35,228(1987).[2]M.Kenzelmannet al,PhysRev.Lett.93,017204(2004);Y.Chenet al,unpublished(2007).

The experiment is of the fundamental interest:The fully polarized 3He has been discussed since theveryolddays,butthe3HeBohrmagnetonsmallnesswoulddemandhugemagneticfieldsforthecompletepolarization.InRep109thesolutionof3Hein4Heformedthedegenerate“Fermigas”atverylowtemperatures;foradilutegasthes-wavescattering istheprevailing interactionbetween 3He-3Heatoms.Onceastrongenoughmagneticfieldorientsallspinsinonedirection,thes-wavescatteringisexcludedduetothePauliprinciple.Thisisthe“trick”theauthorsuseforthedetectionofthefullypolarizedstateinthesolution--themeanfreepathincreasesandthisisseenasthedrasticincreaseintheviscosity.Fullypolarizedstatedubbedas“thehalf-metallic”phaseisassumedastheferromagneticphaseofthecubicmanganitesandsomeothermaterials.Inthatcasetheproofofthe100%-polarizationisfarfrombeingsostraightforwardandsoelegant.• This work was published in Physical Review Letters (2007) and supported by the Magnet Lab’s User Collaboration Grants Program.

giant visCosity EnHanCEMEnt in a spin-polarizEd FErMi liquidH. Akimoto (riKEN, Japan)), J. S. Xia (UF-Physics), D. Candela (University of Massachusetts, Physics), W. B. Mullin (University of Massachusetts, Physics), E.D. Adams (UF-Physics), N. S. Sullivan (UF-Physics)

INTrODUCTIONAtextremelyhighmagneticfields(B~14T)andlowtemperatures(T~2mK)the separation of the spin levels canbecomegreaterthantheFermienergy,and the nuclear spin polarizationtends to unity. As a consequencethe s-wave scattering is stronglysuppressed because only antiparallelpairs can scatter in s-wave orbitalstates and the number of antiparallelpairs drops with increasing spinpolarization. The viscosity along withother transport properties dependson the quasiparticle-quasiparticlescattering and its measurement canprovideasensitivetestofthepredictedsuppression of s-wave scattering atvery lowtemperatures.OneexpectsastrongenhancementoftheviscosityofFermisystemsforconditionsofhighB/T.Dilute3Heinliquid4Heisanalmostidealsampletotestthispredictionforexperimentallyaccessiblemagneticfieldsandtemperatures.

ExPErIMENTALInapreviousstudy1at theNHMFLHighB/T facility,pulsedNMRwasusedtodemonstratetheexistenceofa novel damping of spin currents in 3He-4He mixtures. In this new study2 a special composite vibrating-wire was used to measure the momentum transport (viscosity) in 3He-4He mixtures under similar high B/Tconditions.Herewesummarizethereportsofresultsformeasurementsoftheviscosityusingavibratingwireatverylowtemperatures(2<T<100mK)2.TherequiredexperimentalconditionsweremetusingthenucleardemagnetizationrefrigeratorsoftheNHMFLHighB/Tfacility.

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Figure 1. Variation of temperature dependence of the viscosity of a dilute 3He-4He sample with applied fields in the range 1 to 14.8T.

Figure 1.Phase diagram of CDC showing regions of AFM with inversion symmetry (AFM A), AFM without inversion symmetry (AFM B) ferroelectric polarization, and paramagnetism (PM). Neutron and specific heat data is from Refs. 3,4.

Figure 2.Magnetoelectric current measured on the upsweep of a 50 T short pulse magnet. Consecutive pulses A – F are shown, where the sign of P depends on whether the field sweep is in the same or opposite direction as the previous sweep.

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Sampleswerepreparedfromgaseousmixturestohave200ppm3Heconcentrations.CarefulNMRcalibrationmeasurements at low temperatures established that the condensed samples in the low temperature cellscontained 150 ppm 3He, the difference with the gas concentration being attributed to surface absorptionduringthecondensationprocess.

rESULTS AND DISCUSSIONTheresultsoftheviscositymeasurementsareshowninFigure1.Thedatashowstheexponentialincreaseoftheviscosityforhighspinpolarizations;i.e.forT<10mKandB>11T.Theresultscanbeusedtotesttheoriesoftransportindegenerate,highlypolarizedFermiliquids,andinparticulartestthecurrentmodelsforquasiparticleinteractionsin3He-4Hemixtureswhicharemediatedbyphononexchange.

CONCLUSIONSThe giant enhancement of the viscosity of a prototype dilute Fermi system has been demonstratedexperimentallyfor150ppm 3Heinliquid4He. Thequantitativedependenceis ingoodagreementwiththeexpecteddependenceonpolarizationestimatedfromcurrentmodelsofquasiparticle-quasiparticlescatteringatlowtemperatures.

rEfErENCES[1]AkimotoH.,et al.,Phys.Rev.Lett.90,105301(2003).[2]AkimotoH.,et al.,Phys.Rev.Lett.99,095301(2007).

In samples of Ge implanted with Mn (concentrations of 3% and 6%) the authors have found hugemagnetoresistanceat temperaturesaround~30K.Theeffect isso largethat,accordingtothereport, itcan be described as a transition from a“metallic” state (below 10T) to an insulator-like state at higherfieldsinthistemperaturerange.InterestingresultswerealsofoundfortheHalleffect.Asitisknown,thelatter in a magnetic substance has two components: the normal Hall coefficient stands in front of thelineardependenceontheappliedmagneticfield;thesecondcomponentcalledastheExtraordinaryHallEffect(EHE)isproportionaltothemagnetization.Measurementsinthebroadenoughrangeofmagneticfieldhaverevealedthatthe largemagneticfieldsuppressesEHE.ThereforetheHall resistivitydisclosesthepronouncednon-monotonicdependenceonthefield.Themechanismsresponsible for thisuniquefeatureremainunknown.• This work was supported by the Magnet Lab’s Visiting scientist Program.

HigH FiEld MagnEtotransport in Mn iMplantEd geA. Gerber, o. riss (School of Physics, Tel Aviv University, israel), and A. Suslov (NHMFL)

Thegiantandcolossalmagnetoresistivity(GMR/CMR)remainsoneofthehottopicsinthecondensedmatterphysicsduringthelasttwodecadesbecauseofthegreatvarietyofpotentialandalreadyrealizedapplications(magnetic recording, magnetic field sensors, etc.) and due to many fundamental problems which arise inthe course of the study of various aspects of this multifaceted phenomenon.There are three main classesofsystems,inwhichtheelectricalresistivitychangesbytheorderofmagnitudeorevenmoreinanexternalmagneticfield:(i)multilayeredsystemscontainingferromagneticlayersseparatedbynon-magneticmetalliclayers(ii)granularnanocompositescontainingmagneticgranules;(iii)transitionmetalandrare-earthoxides,inwhichtheelectrontransportissensibletoexternalmagneticfieldinthevicinityofstructural,metal-insulatorandmagneticfieldinducedtransitionsaswellaschargeandorbitalorderingphenomena.Themechanismsofthefieldenhancementorsuppressionofthemagneticscatteringinthesethreesystemsaredifferent,andonemayanticipatethatothermechanismsof(GMR/CMR)mayactinothertypesofmaterialswithnanoscaleinhomogeneity.

ThisworkisdevotedtomagnetotransportingermaniumheavilydopedbyMn.MagnetoresistanceandHalleffectweremeasuredintwosampleswithMnconcentrationof3%and6%infieldsupto33Tandtemperaturesdownto4.2KattheNationalHighMagneticFieldLaboratory.SelectionofmagnetoresistanceandHallresistanceatseveraltemperaturesispresentedinFigures1aandb.

Magnetoresistancedependsstronglyontemperature.Itisrelativelysmallat4.2K,butgrowstothousandsofpercentsaround30Kwiththefurtherreductionathighertemperatures.Magneticfielddrivenmetal-insulatortransitiontakesplaceatfieldsofabout10Twithmetallicstateatlowerfieldsandinsulator-likestateathighfields.Magnetoresistanceriseisverysharpbelow20Kwerethezerofieldmetal-insulatortransitiontakesplaceasafunctionoftemperature.

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Halleffectdataisnotlesspuzzling.BoththeordinaryandtheExtraordinaryHalleffects(EHE)contributetotheshapeandmagnitudeoftheHallresistance.TheEHEcomponentisusuallygeneratedbyspinorbitscatteringby magnetic impurities and ferromagnetic clusters embedded in a conducting matrix. The remarkablefeatureshowninthefigureissuppressionoftheEHEbymagneticfield,resultinginanon-monotonousfielddependence.Tothebestofourknowledgethisisthefirstobservationofsuchphenomenon.

ACkNOwLEDgEMENTSExperimentsatNHMFLweresupportedinpartbyNHMFLVisitingScientistProgram.

Themanipulationandextendedstudyofthepropertiesofoneofnature’smostinterestingstructures,thecarbonnanotube,israpidlybecomingimportanttomanyareasoftechnology,nottheleastofwhichisenergy.Withmanyimportantenergyrelatedapplicationsofcarbonnanotubesrequiringcontrolled,scalableproductionof largequantities, thisHighlightprovidesanewtool forcontrolof somepropertiesof largequantitiesofcarbonnanotubesbasedonNHMFL-levelmagneticfields.

ElECtriCal and MECHaniCal propErtiEs oF MagnEtiC-FiEld alignEd singlE-WallEd Carbon nanotubE buCkypapErsJ.G. Park, X. Fan, S. Li, r. Liang, C. zhang, B. Wang (FSU, HPMi); J.S. Brooks (FSU, Physics)

INTrODUCTIONCarbon nanotube (CNT) is fascinating lightweight material recognized for its low dimensionality with highelectricalandthermalconductivityandexcellentmechanicalproperties.Sheetsofnanotubesornanofibers,knownasbuckypaper(BP),provideapromisingmediumtocontrolthepropertiesofCNT.Severalmethods,suchasalignmentundermagnetic1orelectricfields,e-beamorionbeamirradiation2,areunderinvestigationtoimprovetheelectricalandmechanicalpropertiesofBPtoproducehigh-performancenanocomposites.Inthisresearch,magneticallyalignedBPsupto10”10”wereproducedandtestedtodeterminetheirelectricalandmechanicalpropertiesasafunctionofmagneticfield.

ExPErIMENTALPurifiedHipcoSWCNT(CarbonNanotechnologiesInc.,TX)wasdispersedinanaqueoussolution.ToaligntheCNTs,BPswereproducedunderdifferentmagneticfieldsup to17.3T.ThealignedBPsampleswerecut inrectangularshapesforelectricalandtensiletests.PolarizedRamanwith785nmexcitation(0.5mW)wasusedto check alignment. Electrical conductivity was measured using a conventional four-probe method.Tensilestrengthandmodulusweremeasuredinadynamicmechanicalanalyzer(DMA2980,TAinstruments).

rESULTS AND DISCUSSIONFigure 1 shows normalized G band intensities of aligned BPs from polarized Raman indicating alignmentincreasedasthemagneticfieldincreased.AsshowninFigure2,electricalconductivitywasenhancedbymorethan four times for BP produced in higher magnetic fields. Conductivity anisotropy, , also increased

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Figure 1. Magnetoresistance (a) and Hall effect (b) of MnGe sample with 3% Mn at different temperatures. Arrows indicate the reduction of temperature.

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alongwithmagneticfieldstrength.Mechanicalpropertiesimprovedasaresultofmagneticalignment.Figure3showstensilemodulusandstrengthofalignedBPsincreasedbymorethanfactoroftwo.

CONCLUSIONSBPproductionundermagneticfieldsenhancestheCNTalignment,whichimprovestheelectricalandmechanicalproperties. CNT alignment improves as a function of the magnetic field strength, enhancing electrical andmechanicalpropertiesofBPbymorethanfactoroftwo-four.Theseimprovementsshouldfacilitateproducinghighperformancecomposites.

rEfErENCES[1]Fischer,J.E.,et al.,J.Appl.Phys.93,2157(2003).[2]Krasheninnikov,A.V.,et al.,NatureMat.,6,723(2007).

Three-terminaldeviceswithconductionchannels formedbyquasi-metalliccarbonnanotubes (CNTs)areshowntooperateasnanotube-basedfield-effecttransistorsunderstrongB(upto30T).Anexponentialdecreaseofthedeviceoff-stateconductanceisobservedunderhighaxialBuptoroomtemperature,anditisattributedtotheopeningofanenergygapintheCNTelectronicspectrum.Remarkably,underhighaxialBthedevicesoperateasCNTFETswiththeon/offconductanceratioexceeding104.The temperature dependent magnetotransport is also shown to be a new tool to determine the quasi-metallicnanotubechirality.• This work was published in Nano Letters (2007) and was supported by the Magnet Lab’s user collaboration Grants Program.

Exploring tHE MagnEtiCally induCEd FiEld EFFECt in Carbon nanotubE basEd dEviCEsG. Fedorov (NHMFL), A. Tselev (Georgetown University), D. Jimenez (University of Barcelona, Spain), S. Latil (University of Namur, Belgium), N. Kalugin (New Mexico Tech), P. Barbara (Georgetown University), D. Smirnov (NHMFL) and S. roche (CEA, France)

Theexceptionallow-dimensionalityandsymmetryofcarbonnanotubes(CNT)areattheoriginoftheirspectacularphysicalpropertiesgovernedbyquantumeffects.AjikiandAndo1predictedthatanaxialmagneticfieldwouldtunethebandstructureofaCNTbetweenametalandasemiconductor,owingtothemodulationoftheAharonov-Bohm(AB)phaseoftheelectronicwavefunctions.HerewereportonahighmagneticfieldstudyoftheAB-effectontransportpropertiesofgated(quasi)-metallicsinglewallcarbonnanotubes(SWCNTs)2.

ThemagnetotransportmeasurementswereconductedusingdevicesmadeintheconfigurationofastandardCNTfield-effecttransistor(CNFET),asshowninFigure1.TheconductancecharacteristicsG(Vg)wererecordedattemperaturesfrom1.5Kto290Kandinmagneticfieldsupto30T.

Figure.2showstheconductanceofaCNFETdevice1madewithaquasi-metallicCNT,measuredatthecoaxialmagnetic field. Perpendicular magnetic fields do not significantly change the conductance. Suppression oftheconductancearoundVg*indicatesthepresenceofthenarrowgapinaquasi-metallicCNTatB=0.Astheaxialmagneticfield increases, thegapdecreases to reachaminimumvalueat B0~6T.Device2behavesas

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atrulymetallicnanotubewithB0~0T.AboveB0,aregionofsuppressedconductancedevelops, indicatingamonotonousincreaseofabandgapinbothsamples.Remarkably,underhighaxialmagneticfieldsthedevicesoperateasCNFETswiththeon/offconductanceratioexceeding104.

Qualitatively,theexperimentalobservationsagreewiththepredictedg (B)dependence,andthereforestronglyfavortheinterpretationofourdataintermsoftheABeffect.AquantitativepictureofCNFETmagnetoconductanceisachievedintheframesofamodelincorporatingboththeABeffectonthebandstructureofthenanotubesandtheABeffectonthebarriersformedatthenanotube/contactinterface

To summarize, we report on observation of a magnetic field induced conversion of initially metallic carbonnanotubedevicesintocarbonnanotubefieldeffecttransistors.Strongexponentialmagnetoresistanceobserveduptoroomtemperature is theultimateconsequenceofthe linear increaseofthebandgapwithamagneticfield.ThemagneticfieldcontrolledSchottkybarrierssignificantlycontributetotheCNTmagnetoconductance,whichmaysuggestnewroutestoengineerCNT-baseddevicescharacteristics.Moreover,thisstudyrevealsthetemperature-dependentCNTmagnetotransportasanewtooltoexplorethesymmetriesofcarbonnanotubes.

ACkNOwLEDgMENTSFinancialsupportofthisworkwasprovidedbyNHMFLInHouseResearchProgram,MinisteriodeEducacionyCienciaunderprojectTEC2006-13731-C02-01/MICandNSF(DMR0239721).

rEfErENCES[1]H.AjikiandT.Ando,J.Phys.Soc.Jpn.62,1255(1993)[2]G.Fedorov,et al.,NanoLetters,7,960(2007). CO

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Figure 1. (a) Schematic of a CNFET type device. (b), (c) AFM images of two studied CNFET devices. White arrows indicate direction of the magnetic field.

Figure 2. (a) Plot of the sample 1 conductance versus the gate voltage and the axial magnetic field. A dark arrow indicates the value of B0 , where g(B) has a minimum. (b) Off-state magnetoconductance of sample 1.

Figure 1. Normalized G band polarized Raman intensity along with rotation angle.

Figure 2. Electrical conductivity and its anisotropy of aligned BP as a function of magnetic field.

Figure 3. Tensile modulus and strength of aligned BP as a function of magnetic field.

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Angular dependent resistivity measurements of optimally doped YBCO films in B pulsed up to 50Tprovidethefirstevidence for thepresenceof the liquid-crystallinesmecticphasepredicted for layeredsuperconductors. Inparticular,whenBisalignedwiththelayers,therapidincreaseofthevortexmeltingfieldatlowtemperaturesandthecriticalexponentanalysisconfirmthepresenceofthesmectic.Theyalsoobservethat,uptothehighestBapplied(50T),correlateddefectsarrestthemotionofvorticeswellintotheliquidphase.• This work was published in Physical Review Letters (2007) and was supported by the Magnet Lab’s User Collaboration Grants Program.

sMECtiC vortEx pHasE at HigH FiElds in optiMally dopEd HigH-tEMpEraturE supErConduCtorS. A. Baily, B. Maiorov (NHMFL/STC, LANL); F. F. Balakirev, M. Jaime (NHMFL, LANL); H. zhou, S. r. Foltyn, L. Civale (STC, LANL)

INTrODUCTIONDeep into the superconducting state when a magnetic field is applied it penetrates creating vortices, thatcanexistinsolid,liquid,phases.Thenatureofthesephasesisgivenbythenatureofpinningcenterpresent.1Also, pinning centers enable films to carry more current is an extremely important for applications ofsuperconductivity.ThemostinterestingcaseoccursalongthecopperoxideplanesofHTSwhereallkindsofpinningcentersarepresent.2Whenthemagneticfield,ortemperatureincreasesthevortexlatticecrossesthemeltinglineandbecomesaliquidwiththeconcomitantincreaseoftheelectricalresistance.

ExPErIMENTALElectricalac-transportwasusedtomeasurethevortexdissipationintheliquidphaseaswellastodeterminethemeltingline(wheredissipationgoestozero),asafunctionofangleforYBa2Cu3O7(YBCO)filmsinthe50Tshort-pulsemagnetusingthenewlyrebuiltrotatorprobe.Theeffectofnaturallygrowndefectsonthemeltinglinewasstudied,inparticularforthedefectsalongtheab-planes.

rESULTS AND DISCUSSIONWefindthatnear80K(H>40T),whenthemagneticfieldisalignedwiththelayers,themeltinglinehasanupward turn and the critical exponent that describes the rise in resistivity upon entering the liquid statebecomessimilartothatoftheliquidcrystaltransitionpredictedforlayeredsuperconductors.Alsoweobservethatuptothehighestfieldmeasured(50T)correlateddefectsarrestthemotionofvorticeswellintotheliquidphase.

CONCLUSIONAlong-standingdebateabouttheexistenceofasmecticvortexphasein“lowanisotropy”high-temperature

Figure 1.Left: Normalized resistance vs. scaled field at two temperatures. Right: H vs. Temperature with the magnetic field applied at different orientations.

superconductorbeensettled,withtheevidenceforsmecticvortexphaseinoptimallydopedYBCOatfieldshigherthan40T,availablewithpulsedfield.3

ACkNOwLEDgEMENTSThisworkwassupportedbytheNSFthroughtheNHMFLandNHMFLIHRP,theStateofFloridaandtheDOE.

rEfErENCES[1]G.Blatter,et al.,Rev.Mod.Phys.66,1125(1994).[2]L.BalentsandD.R.Nelson,Phys.Rev.Lett.73,2618(1994).[3]S.A.Bailyet al.,PhysicalReviewLetters(Acceptedforpublication).

CeIn3 has the cubic structure. It is the f-electron antiferromagnet with a considerable hybridization.ChangesintheFermisurfaces’sizesunderappliedpressureorinhighmagneticfieldseenbymeansofthedHvAexperimentprovideinformationaboutcompetitionbetweenitinerancyandthedegreeoflocalizationoftheCef-electrons.TheelectronicpropertiesofCeIn3forthepolarizedphasethatsetsinatstrongmagneticfieldsandtheparamagneticphaseatthepressureabovethecriticalpressure~25kbararedifferent.Inthemagneticfieldsabove~60Tthef-electronsdonotcontributetotheFermisurfaces’volume.Theeffectivemassesgetreducedtothevaluesoffewfreeelectronmassesanddonotvarywiththefieldincrease.ThisresearchisthesignificanttechnicalbreakthroughintheuseofthepulsedmagneticfieldsforthescientificexperimentsandcontainsinterestingnewresultsconcerningCeIn3.• This work was published in Physical review Letters (2007).

MEasurEMEnts on Cein3 in non-dEstruCtivE 100 tEsla MagnEt FiEldsN. Harrison (NHMFL, LANL), C. H. Mielke (NHMFL, LANL), S. E. Sebastian (Cambridge U., Physics), T. Ebihara (Shizuoka Univ., Physics)

Scientists have long since been able to subject materials to the extremes of magnetic field beyond 100tesla, utilizing explosive flux compression or singleturn coil techniques. The destruction of the sample bytheexplosivelydrivensystemsisnotanoptionformany“one-of-a-kind”orotherwise“valuable”samples.Forconductors, however, therapid rates of change ofmagnetic flux broughton by their microsecondduration proves to be anadditional experimentalhurdle to conquer. Ifnot addressed the Jouleheating caused by theinducededdycurrentswillraise the temperature ofthe sample significantly.To counteract theseproblems, high magneticfield scientists around theworldhaveforthepasttwodecades been attemptingto generate magneticfields approaching 100tesla in a controlledfashion,non-destructively,withmillisecondduration.The demands on materialstrength and electricalenergy have provento be much more of achallenge than previously

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Figure 1 The raw dHvA signal in CeIn3 and the spectral analysis. (Inset) The Magnetic Field pulse near peak field showing the ~35 tesla platform field.

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anticipated. Only recently have controlled magnetic fields anywhere near 100 tesla become close to beingrealized.AteamofscientistsandengineersattheLosAlamosbranchoftheNHMFLhavecommissioninga100teslamultishotmagnetwiththeintentionofprovidingslightlyreducedmagneticfieldsof~90Tforexperimentaluseinaninterimperiodbeforethefrontiersarefinallypushedbacktotheirultimategoal.TheseWorldRecordmillisecondpulsedfieldsreachapproximately30teslabeyondwhatwaspreviouslyavailableforexperimentsinpulsedmagneticfieldlaboratories—openingthedoorforcountlessnewopportunities.

CeIn3providesthefirstexampleofasystem,inwhichtemperaturesof~318mK(3/10ofadegreeaboveabsolutezero)enableobservationofthequantumoscillationsinthemagnetization,betterknownasthedeHaasvanAlphen(dHvA)effect.Figure1showsanexampleofrawdataofsuchoscillationsmeasuredinapulseextendingto88tesla.TheFouriertransformoftheoscillationsinFigure2(doneinreciprocalmagneticfield)providesareliablein-situcalibrationofthemagneticfield;thefundamentaldHvAfrequencyF~59.5kTofCuoriginatesfromthewindingsofthedetectioncoilwhilethatofF~3.22kTcorrespondstoasampleofCeIn3alignedwiththefieldisparalleltoits<100>axis.

CeIn3 is of interest because it belongs to a small family of Ce-based antiferromagnets that becomesuperconducting under the application of hydrostatic pressure, just at the point where antiferromagneticorderissuppressed1.Knowledgeonthedegreetowhichthef-electronscontributetotheelectricalpropertiesthroughout is an essential prerequisite for understanding the origin of unconventional superconductivity.Strongmagneticfieldsassistinourpursuitofthisunderstandingbychangingtheextenttowhichthef-electronscontributetoelectricalconductionbypolarizingtheirspindegreesoffreedom.Thispolarizationdepletesthesystemofavailablespindegreesoffreedomforordering,causingtheantiferromagneticordertobesuppressed(asunderpressure).Thisthenmanifestsitselfbywayofsubtlechangesintheelectronicstructurethatcanbeobservedasfield-inducedchangesinthedHvAFourierspectrum.ThisworkwasjointlysupportedbytheNSF,DOE,andFloridaState.

rEfErENCES[1] Harrison,N.,et al.,PhysicalReviewLetters99,056401(2007).

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