nanometer sized effects on magnetic ordering in la–ca manganites, probed by magnetic resonance

Delivered by Ingenta toBen Gurion University of the Negev

IP 1327286183Wed 26 Oct 2011 112508

Copyright copy 2011 American Scientific PublishersAll rights reservedPrinted in the United States of America

Nanoscience andNanotechnology LettersVol 3 531ndash540 2011

Nanometer Sized Effects on Magnetic Ordering inLandashCa Manganites Probed by Magnetic Resonance

E Rozenberg1lowast A I Shames1 and M Auslender21Department of Physics BGU of the Negev P O Box 653 Beer-Sheva 84105 Israel

2Department of Electrical and Computer Engineering BGU of the Negev P O Box 653 Beer-Sheva 84105 Israel

The X-band electron paramagnetic (EPR) and ferromagnetic resonance (FMR) measurements inthe temperature range 5 Kndash600 K were used to explore the nanometer size effects on magneticordering in hole- and electron-doped compounds belonging to the prototypical system of dopedmanganitesmdashLa1minusxCaxMnO3 (x = 01 03 05 and 06) To this end the model fittings of thetemperature dependences of doubly integrated intensity and linewidth of EPR signal as well ascomparative analysis of both FMR data and the known results of neutron diffraction and magneticmeasurements were performed It appears that strongest finite-size effects are observed for low-hole-doped x = 01 nano-crystals due to suppression of chemicalstructural disorder characteristicfor bulk The x = 03 and 05 series demonstrate well pronounced effect of coreshell spin con-figuration on paramagnetic spin correlations and spin dynamics as well as on low temperaturemagnetic ordering The electron-doped x = 06 nano-crystals differ strongly from all other consid-ered nano-samplesmdashthe antiferromagnetic charge ordered ground state was found to be stable inthis case due to supposedly the local nature of double exchange coupling and resulting localizationof carriers

Keywords Magnetism of Nano-Grains Doped La-Ca Manganites Electron ParamagneticResonance Ferromagnetic Resonance

CONTENTS

1 Introduction 5312 Samples and Experimental Details 5333 Results and Discussion 533

31 The Principles of the EPR ParametersModel Fitting 533

32 EPR Parameters Fitting and Discussion 53433 Resonance in the Vicinity of Magnetic Transitions and Low

Temperature FMR Data 5364 Summary and Conclusive Remarks 538

Acknowledgments 539References and Notes 539

1 INTRODUCTION

It is widely accepted now that finite-size effects inducea plethora of new phenomena in the solid-state mag-netism ie when the samplesrsquo size is reduced to thenanometer scale some of their basic magnetic propertiesbecome strongly size dependent and differ markedly fromthe properties of the corresponding bulk material12 Thedoped manganites R1minusxAxMnO3 (here R = La and rare

lowastAuthor to whom correspondence should be addressed

earths A = Ca Sr Ba etc) with mixed valence of Mnions (Mn3+ and Mn4+ demonstrate complex interplay ofspin charge orbital and lattice degrees of freedom whichresults in a rich variety of magnetic electronic and struc-tural phases in their dopant concentrationndashtemperature(xndashT phase diagrams34 In particular the low-doped(x lt 013) compounds belonging to the prototypicalsystem of LandashCa manganitesmdashLa1minusxCaxMnO3 (LCMO)demonstrate canted antiferromagnetic (AFM) insulatingground state5 Upon further increase of Ca-content theferromagnetic (FM) insulating (x gt 013) and FM metal-lic (x gt 0225) phases appear45 The latter phase is sta-ble in a concentration range of 0225 le x lt 05 but thehalf-doped (x = 05) LCMO compound is characterized bymixed magneticelectronic ground state comprising FMand AFM charge ordered (CO) components6 (here COmeans real-space order of charged Mn3+ and Mn4+ ions)If the formal manganese valence is of some rational valuethe CO may also coexist with the orbital ordering (OO)being the spatial order of eg electron orbitals47 In theCa-doping interval of 05 lt x le 08 the AFMCO insu-lating ground state is observed while it transforms tosome mixture of AFM matrix and FM-like clusters for

Nanosci Nanotechnol Lett 2011 Vol 3 No 4 1941-490020113531010 doi101166nnl20111210 531


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Nanometer Sized Effects on Magnetic Ordering in LandashCa Manganites Probed by Magnetic Resonance Rozenberg et al

higher x8 Let us note that so-called lsquoelectron-hole dopingasymmetryrsquo in the phase diagram of LCMO system9 is evi-dent even from the above schematic and very brief descrip-tion Namely the prevailing ground state in the hole-dopedpart (x lt 05) of this diagram is the FM metallic onewhile the AFMCO insulating ground state dominates inthe electron-doped part (x gt 05)

In this work we consider magnetic ordering in LCMOnanoparticles probed mainly by magnetic resonance tech-nique It is believed that the samplesrsquo size reduction iscapable of influencing the magnetic order in doped man-ganites by eg changing the coupling between the spinsubsystem (both Mn ions and carriers spins) and thelattice1011 Recent magnetic studies of such nanoparti-cles evidence on their well pronounced coreshell spinconfiguration1213 Depending on x the double-exchange(DE) FM interaction occurring via hopping of spin-polarized eg electrons between Mn3+ and Mn4+ ions orAFM superexchange between the t2g + eg local spins ofMn3+ ions34 may prevail in the core The shell whichis in general magnetically and structurally mismatchedwith the bulk-like core may exhibit other eg AFM

E Rozenberg is a Grade A Researcher at the Department of Physics Ben-Gurion Universityof the Negev He got his MSc degree from Ural State University in 1971 and PhD degree inPhysics of Magnetism from Institute of Metal Physics (Ural Branch of Academy of Science)in 1983 both in Sverdlovsk USSR He joined Department of Materials Engineering of BGU(Israel) in 1992 and since 1996 ndash Department of Physics His research interests are focusedon magnetism and electrical transport of solid state

A I Shames is a Senior Researcher in charge of the Laboratory of Magnetic Resonanceat the Department of Physics BGU He received his MSc in Theoretical Physics in 1981from the Kishinev State University Moldova and PhD in Solid State Physics in 1987 fromthe Ural State University Russia In 1992 he joined the Department of Physics BGU Hiscurrent research interests focus on magnetic resonance (ESREPREMR NMR) study ofmanganites and nanocarbons (graphene nanotubes nanodiamonds multishell nanographitesetc) coordination compounds spin labeling in biochemistry and biophysics

M Auslender is a Grade A Researcher and Adjunct Professor at the Department of Elec-trical and Computer Engineering BGU He received his PhD in Solid State Physics in1977 from Institute of Metal Physics at Ural Branch of Academy of Sciences USSR In theend of 1991 he joined the Department of Electrical and Computer Engineering BGU Hiscurrent research interests focus on physics of graphene and manganites diffraction gratingsoptical coherence in regular and disordered media and optical sensors

FM or paramagnetic (PM) spin structures The dc and acmagnetic measurements carried out on optimally doped(x sim 03) LCMO nanoparticles13ndash15 revealed notable sizeeffect on the spontaneous magnetization and Curie tem-perature (TC due to the surface magnetic disorder andinterparticle interactions The same mechanisms were sug-gested to be responsible for spin-glass-like properties ofparticles with the lower x= 0216 The mixed ground statewith AFMCO and FM components characteristic for bulkhalf-doped (x = 05) LCMO transforms to FM-like oneupon sample dimensions reduction717 In a marked con-trast AFMCO or AFMOO ground state appears to be sta-ble upon the size reduction in the electron-doped LCMO(x = 075 and 08)1819

Magnetic resonance technique comprising electronPM (EPR) and FM resonance (FMR) is known asa powerful method for study of temperature struc-tural etc dependences of magnetic interactions Thismethod has been used successively for analysis of mag-neticelectronic state(s) in bulk doped manganites begin-ning from mid nineties20 Note that some attempts toapply electron resonance for study of magneticelectron

532 Nanosci Nanotechnol Lett 3 531ndash540 2011


IP 1327286183Wed 26 Oct 2011 112508

Rozenberg et al Nanometer Sized Effects on Magnetic Ordering in LandashCa Manganites Probed by Magnetic Resonance

ordering in nano-sized doped manganites have alreadybeen reported21ndash26 However resonance data were not ana-lyzed in a proper way21ndash2326 or the results of such an anal-ysis seem to be questionable2425 In this context the goalof the present work is to generalize the results of compar-ative study of magneticelectronic ordering in nanometersized and bulk samples of LCMO manganites performedby our group during last few years We addressed the fol-lowing main questions(i) Whatrsquos the relation between specific magneticelectronordering and parameters of EPRFMR in the nano-sizedhole- and electron-doped LCMO(ii) Why the DE interaction enhances in hole-doped nano-crystals but strong enough FM (DE) correlations in thePM state of electron-doped samples have not result in itsFM-like ground state(iii) Whatrsquos the relationship (if any) between the abovenoted effects and chemicalstructural disorder of thespecimens

The paper is organized as follows Section 2 describesbriefly the experimental details of nano-samples prepara-tion and characterization as well as the resonance tech-nique used in Section 3 the experimental EPR data andtheir model analysis the behavior of electron resonancein the vicinity of magnetic transition temperatures and thelow-T FMR data are presented Section 4 contains sum-mary and conclusive remarks

2 SAMPLES AND EXPERIMENTAL DETAILS

In this work we have employed the crystalline nano-powders of LCMO with Ca-doping level of x = 01 0305 and 06 (labeled further as Ca01 Ca03 Ca05 andCa06) prepared by the sonication-assisted coprecipitationand the subsequent crystallization27 In this method thechemical effect of ultrasound arise from acoustic cavita-tion ie the formation growth and implosive collapseof bubbles in liquid (homogeneous colloidal suspensionof precursors) the above collapse generates localized hotspots inducing local chemical reaction(s)28 The amor-phous product of the above process was crystallized usingannealing at 700ndash800 C in air during 1ndash2 hours Thestructures and sizes of the obtained LCMO nano-crystalswere controlled by room-T X-ray diffraction their aver-aged cation compositions were examined by electron dis-persive X-ray analysis and inductively coupled plasmaatomic emission spectroscopy techniques as describedpreviously1011 Note that relatively small mean grain sizes(not exceeded of about 28 nm) of the nano-samples stud-ied were chosen for an enhancement of the size effect onthe magnetic order The bulk LCMO single crystals andceramics used in our comparative studies were synthe-sized by the radiative heating floating-zone method29 andby standard solid state reaction respectively

Resonance measurements were performed with BrukerEMX-220 X-band ( = 94 GHz) spectrometer in theT -range between 5 and 600 K using few milligrams ofthe loose-packed nanometer-sized grains or micron-sizedpowdered bulk samples as described earlier30 The loose-packed form of the powder samples enables one to excludethe influence of the skin effect and to narrow the signalsin the FM state due to the texture of fine particles inthe external magnetic field (H This in turn gives onean opportunity to examine a complex resonance signal inmore details In the course of the experiments we haveanalyzed the T -dependences of the following resonancespectra parameters(i) doubly integrated intensity (DIN) of the signal(s) pro-portional to the transverse magnetic susceptibility (such proportionality is especially important for our analy-sis of the PM spin correlations31

(ii) peak-to-peak linewidth (Hpp describing the concur-rent spin dynamics of both Mn ions and carriers(iii) resonance field (Hr which appears to be constantin the PM state and shows notable shift near the TCattributed usually to the internal magnetic fields due to thelong range FM order In addition the EPR DIN and Hpp

versus T dependences were analyzed using the modelapproach32

3 RESULTS AND DISCUSSION

31 The Principles of the EPR ParametersModel Fitting

It appears that in all LCMO compounds considered fur-ther independently on their bulk or nanometer-sized struc-tural state the EPR signal is a singlet Lorentzian shapedline at temperatures far above the critical T of mag-neticelectronic phase transition(s) This Lorentzian line ischaracterized by the same temperature independent PMg-factor g = 199plusmn001 (Hr = const) Such g-factor valueis typical for Mn4+ in the (O2minus6 octahedron coordination33

indicating that the majority of eg electrons leave Mn3+

ions and become either itinerant or localized outside theMn4+ ions It was argued10 that in this case and forHr Hpp

DIN prop MT HrT

HrT = perpT HrT (1)

Here MT H and perpT H are the thermodynamicmagnetization and transverse magnetic susceptibilityEquation (1) shows that in our case DIN can be definitelytreated as EPR measured PM susceptibility

Two main types of the inverse DIN versus T depen-dences are characteristic for our nano-crystals the lin-ear (or piecewise linear) and non-linear one with thenon-linearity enhanced upon cooling The former depen-dences were fitted to the standard Curie-Weiss (CW) law

Nanosci Nanotechnol Lett 3 531ndash540 2011 533


IP 1327286183Wed 26 Oct 2011 112508


DIN prop = CT minus where C and are Curie constantand CW temperature respectively The latter data wereanalyzed using the Neacuteel PM-susceptibility formula

minus1 = Cminus1

(T minusminus 2

T minus

)(2)

applied previously for description of the magnetic34 andEPR35 susceptibilities in different doped manganites Notethat applicability of Eq (2) originally proposed fordescription of T dependences in ferrites36 evidencesthat two different magnetic subsystems present in consid-ered nano-samples This point is discussed in more detailin the next sub-section

To model the PM spin dynamics (Hpp versus T inthe studied nano-crystals we have used the approach byHuber et al37 according to which

HppT = 0T T 13LT (3)

where 0T = CT minus1 is the Curie and T is the actualsusceptibility and

LT =int

0

TtT0TS2

Tdt (4)

It is the integral of normalized time-correlation func-tion of random torques Tt which cause either compo-nent of total spin of the system St to relax and thebrackets mean thermodynamic average with the tempera-ture T Note that in bottleneck regime caused by strongexchange interactions St is a unique quantity for theEPR description37

It appears that the original Huber et al paradigm37

which replaces LT over the PM range (T gt by theconstant high-temperature asymptote H doesnrsquot workwell for the most studied nano-samples It was shown32

that the excess charge carriers may drastically modifyLT as compared to the approximation37 In such casesto model the surplus carriers-assisted mechanism of spinrelaxation we add to the independent of T pure ion spin-spin relaxation term37 one describing the contribution ofthermally excited mobile eg electrons

LT = H+BT (5)

Here H is a constant calculated as described inRef [37] and B is a parameter of effective spin-orbitinteraction between eg electrons and impurities with spin-reversal10 To include the option of two exchange-coupledmanganese spin subsystems in some of our samples weused in Eq (3) just the Neacuteelrsquos expression (2) and Eq (5)which yields the following model temperature dependenceof the PM linewidth

HppT =(T minusminus 2

T minus

)(H

T+B

)(6)

This equation in fact incorporates all the cases of our inter-est eg the case encountered in Ref [37] is that withone localized-spin subsystem ( = 0) and no effect of thecarriers (B = 0) Further on the Eq (6) will be used anddiscussed in the course of fitting procedures

It is worth noting here that a reasonable fitting ofthe PM DIN(T and HppT dependences recorded onCa01 bulk crystal requires taking into account the notablespatial variations of Ca-doping level through the volumeof this sample1038 Such results are presented in thiswork only for comparison with the corresponding analysisfor Ca01 nano-sample Readers interested in details areaddressed to the above noted papers

32 EPR Parameters Fitting and Discussion

Note that the PM state is well defined precursor ofthe low-T magneticelectronic order in our LCMO nano-samples which emphasizes an importance of the PM spincorrelations and spin dynamics study The measured PMDINminus1T and HppT dependences together with theirmodel fits are presented in Figures 1 and 2 respectivelyA strong difference between the shapes of DINminus1 andHpp versus T curves in nano- and bulk Ca01 sam-ples definitely weakens and becomes almost unobserv-able upon increase of Ca-doping level and transition fromhole- to electron-doped LCMO compoundsmdashcompareeg pair of Figures 1(a) and (e) with corresponding one ofFigures 1(d) and (h)mdashthe same in Figure 2 This findingconfirms that a notable weakening of size induced effect(s)on magnetic ordering is observed in LCMO system versusCa-doping Such conclusion is strongly supported by theresults of model fittings (best fits data) collected for clarityin Tables I and II together with the structural parametersand temperatures of magneticelectronic transitions for allstudied nano- and bulk samples

Let us discuss briefly the results obtained The abovenoted strong difference between the DINminus1 versus Tdependences in Ca01 nano- and bulk samples mani-fests in respective piecewise linearity of the curve inFigure 1(a) and in appearance of two T -regions of CW-likeregimes with smeared step like transition between themin Figure 1(e) The HppT curves recorded on thesesamples may be characterized as follows linewidth ofthe nano Ca01 shows step like anomaly neat 500 Kand further continuous decrease down to about 250 Kin Figure 2(a) At the same time the HppT of thebulk goes through a broad minimum at T = 420 K andthen decreases monotonously down to about 175 K uponcooling see Figure 2(e) We have explained these fea-tures using the model of transition from chemically disor-dered bulk crystal to more homogeneous nano-crystals10

As a result a transition from an inhomogeneous state ofcharge carriers confined by imperfections in bulk to a more



IP 1327286183Wed 26 Oct 2011 112508


200 400 600

2

4

400 600

06

12

300 40000

03

300 400

03

06

400 6000

0

1

400 60000

06

12

200 400 6000

1

2

400 600

08

16

06

(a) Ca01nano

Ca06bulk

(h)

Ca05nano

Ca05bulk

(g)

Temperature T (K)

Ca03nano

(d)

(c)

(b) Ca03bulk

(f)

Ca01bulk

(e)

Ca06nano

Nor

mal

ized

DIN

ndash1

Fig 1 Temperature dependences of the inverse DIN of the EPR signalnormalized to its values at T = 500 K (circles and stars) and their fits(lines) for (a) and (e)mdashCa01 nano-crystals and bulk (b) and (f)mdashCa03nano-crystals and bulk (c) and (g)mdashCa05 nano-crystals and bulk (d)and (h)mdashCa06 nano-crystals and bulk The fitting procedures are dis-cussed in the text the arrows in (a) and (e) point out Jahn-Teller transitionoriginated features

mobile one in an impurity-like band in nano Ca01 occurswhich is seen in Table I as a zeroing of activation energyof carrier spin-lattice relaxation process upon transitionfrom bulk- to nano-crystalline state in Ca01 An impor-tant point is also a transformation of smeared cooperativeJahn-Teller transition (JTT) in chemicalstructural inhomo-geneous bulk to the JTT in nano Ca01 characterized bythe electron component only10 (the JTT originated featuresare pointed out by arrows in Figs 1 and 2)

The PM DINminus1T dependences in Ca03 andCa05 nano-crystals prove essentially non-linearmdashFigures 1(b) and (c) which allows us to use the Neacuteelformula (2) It was noted already that its applicabilityevidences on two different magnetic subsystems whichpresent in these nano-samples The most probable candi-dates are Mn ions in the cores and in the surface-like shellsof the grains which will thus be labeled by the indexes lsquocrsquoand lsquosrsquo Here C =Cc+Cs Ccand Cs being the subsystemsrsquoCurie constants and are known35 combinationsof Cc Cs the subsystemsrsquo CW temperatures c s andthe inter-subsystems exchange coupling i (in Kelvin

400 600

04

08

12

400 600

04

08

12

400 600

04

08

12

400 600

08

12

400 600

08

12

16

400 600

04

08

200 400 600

04

08

12

16

200 400 600

08

12

Ca03nano

(c)

(b)

Ca05nano

Ca05bulk

Ca06bulk

(h)Ca06nano

(d)

Ca03bulk

Temperature T (K)

Ca01nano

(a)

Ca01bulk

(g)

(f)

(e)

Lin

ewid

th Δ

Hpp

(kG

)

Fig 2 The same as in the Figure 1 for the paramagnetic linewidths

degrees)mdashsee Tables I and II The main point of thisanalysis is proving the FM intra-systems coupling withc gt s in core and shell and the AFM inter-subsystemsrsquoone i lt 0 Appearance of these two exchange coupledmagnetic subsystems in the Ca03 and Ca05 samplesforces us to use the modified formula (6) for analysisof PM HppT curves recorded on these samplesmdashFigures 2(b) and (c) Now the parameters H and B

in Eq (6) characterize a total contribution of core andsurface spins to pure ion-ion spin relaxation37 and to relax-ation due to an interaction between the eg electrons andimpurities with spin-reversal32 respectively The physicalparameters presented in Tables I and II and marked aslsquoroughrsquo ones were extracted using the rough assumptionsB = BC = BbCcC and H

c = Hb CcC where lsquobrsquo

marks the corresponding values for the bulk Ca03 andCa05 samples derived from the fits of experimental datain Figures 2(f) and (g) to Eqs (3) and (5) Thus the mainfeature distinguishing Ca03 and Ca05 nano-crystalsfrom its bulk counterparts is strong coreshell effectsThese effects(i) modify DINminus1T curves markedly in our nano-sizedsamples as compared to corresponding CW like depen-dences in bulk as seen in Figures 1(b) (c) (f) and (g)and



IP 1327286183Wed 26 Oct 2011 112508


Table I Hole-doped LCMO compounds The Curie and Neel (transition to canted AFM structuremdashTCA temperatures T0mdashestimated temperature ofcooperativeelectron Jahn-Teller transition (in bulk Ca01 T0 corresponds to average Ca content and is the smearing interval of the above transition)lattice parameters of orthorhombic Pnma structure and parameters of the fits for Hpp and DINminus1 The parameters are 12 are the Curie-Weiss (CW)temperatures below and above the JT transition c and s are respective core and shell CW temperatures while i is the inter-subsystem coupling inT -units A is the parameter of ion spin-carrier-orbit interaction B is the parameter of carrier spin-lattice interaction and EA is the activation energy forthis process

Sample Ca01-nano Ca01-bulk Ca03-nano Ca03-bulk

Size (nm) 24plusmn4 mdash 15plusmn2 mdash

a b c (Aring) 5465 (2) 7739 (3) 5506 (3) 5593 (1) 7730 (1) 5527 (1) 5461 (2) 7725 (2) 5479 (2) 5463 (1) 7744 (1) 5468 (1)Pnma notation

TCA (K) 113plusmn1TC (K) 90plusmn2 130plusmn2 233plusmn2 239plusmn2

(K) 1 = 210plusmn2 1 = 140plusmn2 c asymp 258 247plusmn22 = 145plusmn5 2 = 142plusmn6 s asymp 228

i asympminus50

T0 (K) 463plusmn6 366plusmn2 mdash mdash(= 40plusmn4)

Hpp (G) 1165plusmn45 1734plusmn17 H asymp 1093 0

Hs asymp 1454

A (G) 0 0 mdash 110plusmn3

B (GKminus1 15plusmn01 148plusmn10 asymp183 283plusmn002

EA (meV) mdash 377plusmn32 mdash mdash

(ii) notably change the values of the parameters H

and B describing different mechanisms of the PM spinrelaxation see Tables I and II

In a strong contrast to the hole- and half-dopedLCMO size effects on the PM spin correlations andspin dynamics are markedly suppressed in electron-dopedCa06 nano-crystals One can note using the data inFigures 1(d) 1(h) 2(d) 2(h) and in Table II that aboutthe same CW like DINminus1T dependences with close andpositive and the similar HppT curves are observedin nano- and bulk Ca06 The basic question ldquoWhy theFM like correlations in the PM state of these samples donot result in a long range FM order at lower T rdquo will bediscussed further

Table II Half- and electron-doped LCMO compounds The Curie Neel and charge ordering temperatures lattice parameters of orthorhombic Pnma

structure and parameters of the fits for Hpp and DINminus1 The parameters are is the Curie-Weiss (CW) temperature c and s are respective coreand shell CW temperatures while i is the inter-subsystem coupling in T -units His high temperature asymptote of Mn4+ ions spin-spin relaxationcontribution B is the parameter of carrier spin-lattice interaction




TC (K) 245plusmn2 250plusmn2TN (K) 152plusmn2 152plusmn2TCO (K) 198plusmn3 260plusmn2

(K) c asymp 262 255plusmn3 (DINminus1 213plusmn3 (DINminus1 211plusmn5 (DINminus1

s asymp 248 252plusmn1 (Hpp 205plusmn2 (Hpp 208plusmn2 (Hpp

i asympminus8

H (G) H asymp 1454 1134plusmn60 2368plusmn18 2183plusmn17H

s asymp 2407

B (GKminus1 asymp147 195plusmn009 mdash mdash

33 Resonance in the Vicinity of Magnetic Transitionsand Low Temperature FMR Data

Resonance spectra recorded in the vicinity of the Curiepoints on Ca03 bulk crystal and nano-sample are shownin Figures 3(a) and (b) respectively The basically impor-tant fact is a coexistence of PM-type (EPR) and FM-type(FMR) signals within T sim 10 K in crystal and theabsence of such coexistence in nano Ca03mdashjust the sin-glet symmetric EPRFMR line is observed in a wideenough T -range of 220ndash250 K upon crossing TC sim 233 KRecently Alejandro et al39 reported on suppression ofsimilar resonance signals coexistence in bulk ceramics ofnear optimally doped La-(Ca Sr) manganites upon thechange of crystal structure (due to the Sr-content increase)



IP 1327286183Wed 26 Oct 2011 112508


ndash15

00

15

30

ndash30

ndash15

00

15

30

ndash150

ndash75

00

75

150

0 2 4 60 2 4 6ndash10

ndash5

0

5

10

ν = 9434 GHz

(a) T = 240 KT = 2425 K T = 245 K T = 2475 K

ν = 9438 GHz

T = 220 KT = 230 KT = 240 KT = 250 K

240 K

ν = 9463 GHz

(b)

(c)

160 K

240 K

160 K

ν = 9464 GHz

(d)

Magnetic field H (kG)

Res

onan

ce s

pect

ra in

tens

ity (

Arb

Uni

ts)

Fig 3 The differentional resonance spectra measured in the vicinityof the ferromagnetic transition on (a) and (b)mdashCa03 bulk and nano-crystals (c) and (d)mdashCa05 bulk and nano-crystals The arrows in (c) and(d) show the direction of measuring temperature increase (the changeof such temperature upon transition to the next spectra recording isT = 10 K)

from orthorhombic to more symmetric rhombohedral oneThe data in Figures 3(a) and (b) as well as results4041

definitely evidence that such suppression is valid alsofor orthorhombic optimally doped LCMO upon transi-tion to nanometer sized samples We have argued4041 thatthe nature of such suppression is technologically drivenimprovement of chemical and structural homogeneity ofnano-crystals prepared by sonication-assisted coprecipita-tion as compared with corresponding bulk crystals andceramics2930 One can find additional strong and expres-sive argument in favor of the above claim in Figures 3(c)and (d) Namely the EPR and FMR signals coexist inCa05 bulk ceramic in a very wide T -range of 160ndash240 K below its TC while the singlet EPRFMR line isrecorded for Ca05 nano-crystals (having similar TC valuesee Table II) in the same T -intervalmdashFigure 3(d)

Additional important information on the difference inthe resonance properties of our nano-samples as com-pared with corresponding bulk may be extracted fromFigure 4 In general it appears that below the tempera-tures of magneticelectronic phase transitions in bulk theFM like resonance signals are splitted to low- and high-field components see Figures 4(a) (c) and (d) or suchsignal shifts sharply to low-field region upon coolingmdashFigure 4(b) It was suggested542 that the complex effect ofFM magneto-crystalline and shape anisotropies is respon-sible for the above Hr versus T behavior in bulk LCMOsamples In a contrast one can definitely note that theLCMO nano-crystals are characterized(i) by the absence of the above noted splitting of the FMRlike line and(ii) by the notably weaker low-field shift of such sig-nalsrsquo Hr upon coolingmdashcompare corresponding datain Figure 4 This definitely means that sonochem-ically prepared LCMO nano-crystals are not only

10

20

30

40

50

20

25

30

35

0 200 400 600

10

20

30

40

50

0 200 400 600

10

20

30

Ca01(a)

Bulk PM Line Bulk FM line Bulk FM Line Nano

Ca03

(c)

(b) Bulk PM Line Bulk FM line Nano

Ca05


Temperature T (K)

Ca06

(d) Bulk PM Line Bulk FM line Bulk FM Line NanoR

eson

ance

fie

ld

Hr (k

G)

Fig 4 Temperature dependences of the resonance fields characterizingthe different resonance signals recorded on a whole series of the samplesstudied

more chemicalstructural homogeneous but also are lessanisotropic as compared to bulk due to eg suppressionof their shape anisotropy

It seems that the data on normalized DIN versusT dependences presented in Figure 5 in the wholeT -interval of our measurements are most informativeregarding the low-T magneticelectronic order in consid-ered LCMO samples Let us remind that DIN is propor-tional to the transverse magnetic susceptibility measuredat high frequency (sim94 GHz)510111439 also at low tem-peratures The following basic facts may be noted(i) the low-T DIN measured on nano-crystals exceedmarkedly corresponding values for its bulk counterpartsin the case of Ca01 Ca05 and Ca06 compounds seeFigures 5(a) (c) and (d) respectively While the FMRsignal intensity of optimally doped Ca03 bulk is definitelyenhanced comparing to those in nanomdashFigure 5(b)

0

100

200

0

100

200

0 200 400 600

0

150

300

0 200 400 60000

25

50

Ca01

Bulk

Nano

(a)

(NI

DT

)K

005(NI

D)

Ca03

(b)

Ca05

(c)

Ca06

(d)

Temperature T (K)

Fig 5 Temperature dependences of the DIN of the EPRFMR signalsnormalized to its values at T = 500 K measured on a whole series of thesamples studied The arrows in (c) and (d) point out the weak lsquoshouldersrsquoon DIN(T curves for Ca05 and Ca06 nano-crystals near the tempera-tures of DINsrsquo maxima for corresponding bulk samples



IP 1327286183Wed 26 Oct 2011 112508


(ii) the DIN(T dependences of Ca01 Ca03 and Ca05nano-crystals demonstrate broadened maxima shifted tolower temperatures as compared to the correspondingcurves for bulkmdashFigures 5(a)ndash(c) At the same timethe maximum on DIN(T in Ca06 nano is also shiftedto lower T but continues to be narrow in shape seeFigure 5(d)(iii) at last the lowest-T DIN values in hole- and half-doped LCMO are enhanced in more than an order of mag-nitude as compared to DIN detected on electron-dopedCa06 compound

The maximal enhancement of the FMR DIN(T whichis observed for Ca01 nano-crystals [Fig 5(a)] exists dueto the suppression of an inhomogeneous confined state ofcharge carriers in bulk and appearing of FM like groundstate with the TC sim 90 K in nano (remind that canted AFMmatrix is characteristic for bulk crystal of Ca01 below ofsim113 K4510 and Table I) The transformation of mixedground state with AFMCO and FM components char-acteristic for bulk Ca05 to FM like one in nano71743

explains in a natural way the DIN rise in this very caseMoreover an increase of low-T magnetization from sim17to sim50 of its theoretical value upon transition from bulkto nanometer size samples of Ca057 is in line with thedata in Figure 5(c) While the stable FM metallic phasein bulk optimally doped Ca03 only frustrates upon transi-tion to nanometer size state due to the appearance of FMdisordered shell12ndash15 and Table I which is responsible forthe change in FMR DIN shown in Figure 5(b) The abovenoted shift of the broadened DIN(T maxima far below theTC values observed for hole- and half-doped LCMO nano-crystals in Figures 5(a)ndash(c) definitely resembles the low-Tshift of the ac magnetic susceptibility maxima measuredpreviously on Ca031444 and Ca05717 nano-samples [letus mention a weak lsquoshoulderrsquo recorded on FMR DIN(T for Ca05 nano near the temperature of correspondingDINsrsquo maximum for bulk in Fig 5(c)] Note also thatthe frequency (f dependences recorded in the vicinity ofthe ac T maxima in all these cases are inconsistentwith usual (spin glass-like originating) shift of this peakto higher T versus f 744 These features of both DIN(T and ac T dependences may be clearly explained by astrong competition of the corresponding responses of FMordered Mn ionsrsquo spins in cores and partially disorderedones (with lesser ndash Tables I II) in shells together withthe surface electron tunneling between adjacent grains inagglomerated nano-samples10

It was noted already that the low-T magnetic orderingin Ca06 nano-crystals seems to be qualitatively differentfrom the FM like one in other considered nano-samplesUsing the phase diagram of electron-doped bulk LCMO8

together with the results of model fits in Figures 1 and 2one can suggest the following High concentration ofdoped electrons results in appearance of FM correlationsin PM state of our Ca06 nano and bulk samples as indi-cated by positive values of in Table II which in general

is a result of DE coupling It seems that such coupling inCa06 has a localized nature due to the excellent descrip-tion of its PM spin relaxation (Hpp versus T dependence)in Figures 2(d) and (h) by Huber like37 formula (3) tak-ing into account only ion-ion spin relaxation mechanismThis in turn confirms the minority nature of band-likecharge carriers and hence indicates the local nature of DEcoupling Comparison the results of our resonance andmagnetic measurements performed on bulk and nano-sizedCa0611 and the data of magnetic measurements on nano-sized electron-doped Ca075 and Ca08 samples181945

allows us to suggest the following Upon cooling theCO correlations between Mn4+ and Mn3+ ions begin todevelop and to compete with the local FM ones and thelong-range CO becomes stable in the Ca06 nano-crystalsonly below their sim 200 K which manifests itself in thesharp peak of DIN(T in Figure 5(d) at Tmax sim 185 KThis is the CO correlations in the nano Ca06 weaken ascompared with those in the bulk for which Tmax asymp TCO =260 KmdashFigure 5(d) Further cooling results in appearanceof AFM correlations within CO cores of Ca06 grainswhich induces sharp decrease of DIN below 185 K asit was observed previously for electron-doped (x = 08)bulk LCMO46 The lsquoshoulder-likersquo anomaly on DIN(T curve in sim100ndash70 K interval [Fig 5(d)] may be associ-ated with the stabilization of the long-ranged AFM orderin the cores of Ca06 grains Note the non-zero inten-sity of FMR signal at lowest T revealed for both nano-and bulk Ca06 in Figure 5(d) Accepting the model ofAFMFM like coreshell spin configuration which realizesin electron-doped nano LCMO at low temperatures181945

one can suggest that the above FM like spin order in theshell induces a pronounced increase of low-T DIN val-ues in nano Ca06 as compared with bulk At the sametime the presence of minor charge disordered FM phasein bulk Ca0647 may be responsible for its weak FM likeresonance signal at low temperatures

4 SUMMARY AND CONCLUSIVE REMARKS

The results presented in this paper allow us to con-clude the following Using the prototypical system ofLa1minusxCaxMnO3 manganites we have managed to showthat the strongest effect of transition from bulk to nanome-ter sized state on magnetic ordering is observed in low-hole-doped samples (here lsquolowrsquo means the Ca-dopinglevel lower than critical one for appearance of ferro-magnetic metallic state) Such bulk crystals are character-ized by notable inhomogeneity of Ca-dopant distributionresulting in chemicalstructural disorder which influencesstrongly its magnetic order10293138 Our sonochemicallyprepared nano-crystals appear to be more homogeneouswhich results in strong modification of PM spin corre-lation and spin dynamics and induces FM like groundstate in low-hole-doped Ca01 see 32 and Table I The



IP 1327286183Wed 26 Oct 2011 112508


coreshell effects characteristic for nanometer sized dopedmanganites manifest itself in this case mainly in coex-istence of a broad Gaussian and narrow Lorentzian reso-nance signals10

In a contrast these coreshell effects are definitelyenhanced in optimally doped Ca03 and half-dopedCa05 nano-crystals supposedly due to relatively highmagnetization values This enhancement manifests in thestrong modification of paramagnetic DIN(T dependences(lsquoNeacuteel-typersquo curve) signaling on coexistence of differentmagnetic subsystems see 32 Tables I and II It is worthnoting here that using the model approach32 for analysisof PM DIN and linewidth allowed us to estimate quan-titatively the parameters of the coreshell spin configura-tions in Ca03 and Ca05 nano-crystals It appears thatcore and shell spin subsystems are FM intra-correlated(with notably reduced temperature of magnetic orderingin the shell) and AFM inter-correlated The improvementof nano-crystalsrsquo homogeneity as compared to bulk leadsin this very case mainly to suppression of the FMR andEPR signals coexistence in the vicinity of the Curie pointsee Figure 3

The influence of nanometer size effects is definitely sup-pressed in the case of electron-doped Ca06 Namely theAFMCO ground state appears to be stable in spite ofwell pronounced FM spin correlations in the PM staterevealed by our model analysis We suggested that a localnature of DE coupling and resulting localization of car-riers in electron-doped LCMO are responsible for thiseffect This finding together with the elastic interactionsbetween Jahn-Teller ions and orbital ordering describedby Khomskii et al948 may be considered as a prereq-uisite for the electron-hole doping asymmetry effect inLCMO system The coreshell effects cause only someenhancement of FM like low temperature resonance signalin Ca06 nano-crystals

Acknowledgments We sincerely acknowledge Profes-sor A Gedanken Professor Ya M Mukovskii and Dr ESominski for synthesis of the samples We would also liketo thank Professor I Felner and Dr M I Tzindlekht forhelp in magnetic measurements and Dr D Mogilyanskyfor X-ray characterization of the samples

References and Notes

1 R H Kodama J Magn Magn Mater 200 359 (1999)2 X Batlle and A Labarta J Phys D 35 R15 (2002)3 J Coey M Viret and S von Molnar Adv Phys 48 167 (1999)4 E Dagotto Nanoscale Phase Separation and Colossal Magnetore-

sistance Springer Series in Solid State Physics Springer-VerlagBerlin Heidelberg (2002) Vol 136

5 V Likodimos and M Pissas Phys Rev B 76 024422 (2007)6 Q Huang J W Lynn R W Erwin A Santoro D C Dender V N

Smolyaninova K Ghosh and R L Greene Phys Rev B 61 8895(2000)

7 Z Jiraacutek E Hadovaacute O Kaman K Kniacutežek M Maryško andE Pollert Phys Rev B 81 024403 (2010)

8 M Pissas and G Kallias Phys Rev B 68 134414 (2003)9 D Khomskii Int J Mod Phys B 15 2665 (2001)

10 E Rozenberg A I Shames M Auslender G Jung I FelnerJ Sinha S S Banerjee D Mogilyansky E SominskiiA Gedanken Ya M Mukovskii and G Gorodetsky Phys Rev B76 214429 (2007)

11 E Rozenberg M Auslender A I Shames D MogilyanskyI Felner E Sominskii A Gedanken and Ya M Mukovskii PhysRev B 78 052405 (2008)

12 M Muroi P G McCormic and R Street Rev Adv Mater Sci 5 76(2003)

13 P Dey and T K Nath Phys Rev B 73 214425 (2006)14 E Rozenberg M I Tsindlekht I Felner E Sominskii

A Gedanken and Ya M Mukovskii IEEE Trans Magn 43 3052(2007)

15 D Markovic V Kusigerski M Tadic J Blanusa M V Antisariband V Spasojevic Scripta Mater 59 35 (2008)

16 V Markovich I Fita A Wisniewski G Jung D MogilyanskyR Puzniak L Titelman and G Gorodetsky Phys Rev B 81 134440(2010)

17 E Rozenberg M I Tsindlekht I Felner E Sominski A GedankenYa M Mukovskii and C E Lee IEEE Trans Magn 45 2576(2009)

18 T Zhang T F Zhou T Qian and X G Li Phys Rev B 76 174415(2007)

19 V Markovich I Fita A Wisniewski D Mogilyansky R PuzniakL Titelman C Martin and G Gorodetsky Phys Rev B 81 094428(2010)

20 S B Oseroff M Torikachvili J Singley S Ali S-W Cheong andS Schultz Phys Rev B 53 6521 (1996)

21 L Malavasi M C Mozzati S Polizzi C B Azzoni and G FlorChem Mater 15 5036 (2003)

22 S S Rao K N Anuradha S Sarangi and S V Bhat Appl PhysLett 87 182503 (2005)

23 O Raita M N Grecu X Filip D Toloman L M GiurgiuS Idziak and S K Hoffmann Acta Phys Polon A 108 113(2005)

24 T Tajiri H Deguchi S Kohiki M Mito S Takagi M MitomeY Murakami and A Kohno J Phys Soc Jap 77 074715 (2008)

25 J Kurian and R Singh J Appl Phys 105 07D718 (2009)26 S S Rao and S V Bhat J Phys D Appl Phys 42 075004 (2009)27 G Pang X Xu V Markovich S Avivi O Palchik Yu Koltypin

G Gorodetsky Y Yeshurun H P Buchkremer and A GedankenMater Res Bull 38 11 (2003)

28 S Avivi Y Mastai G Hodes and A Gedanken J Amer ChemSoc 121 4196 (1999)

29 D Shulyatev S Karabashev A Arsenov Ya M Mukovskii andS Zverkov J Cryst Growth 237239 810 (2002)

30 A I Shames E Rozenberg W H McCarroll M Greenblatt andG Gorodetsky Phys Rev B 64 172401 (2001)

31 E Rozenberg M Auslender A I Shames G Gorodetsky andYa M Mukovskii Appl Phys Lett 92 2222506 (2008)

32 M Auslender A I Shames E Rozenberg G Gorodetsky andYa M Mukovskii IEEE Trans Magn 43 3049 (2007)

33 A I Shames M Auslender E Rozenberg G GorodetskyS Heacutebert and C Martin J Magn Magn Mater 316 e640 (2007)

34 H Aliaga M T Causa M Tovar A Butera B Alascio D VegaG Leyva G Polla and P Koumlnig J Phys Condens Matter 15 249(2003)

35 A I Shames M Auslender E Rozenberg E SominskiA Gedanken and Ya M Mukovskii J Appl Phys 103 07F715(2008)

36 S V Vonsovskii Magnetism Wiley New York (1974) Vol 2Chap 22



IP 1327286183Wed 26 Oct 2011 112508


37 D L Huber G Alejandro A Caneiro M T Causa F PradoM Tovar and S B Oseroff Phys Rev B 60 12155 (1999)

38 M Auslender A I Shames E Rozenberg G Gorodetsky andYa M Mukovskii J Appl Phys 105 07D705 (2009)

39 G Alejandro M Otero-Leal M Granada D Laura-CcahuanaM Tovar E Winkler and M T Causa J Phys Condens Matter22 256002 (2010)

40 E Rozenberg A I Shames G Jung Ya M MukovskiiE Sominski A Gedanken and Ch E Lee Phys Stat Sol B244 4554 (2007)

41 A I Shames E Rozenberg Ya M Mukovskii E Sominski andA Gedanken J Magn Magn Mater 320 e8 (2008)

42 A I Shames E Rozenberg G Gorodetsky and Ya M MukovskiiPhys Rev B 68 174402 (2003)

43 M Auslender A I Shames E Rozenberg E SominskiA Gedanken and Ya M Mukovskii J Appl Phys 107 09F702(2010)

44 D Markovic V Kusigerski M Tadic J Blanusa Z JaglicicN Cvjeticanin and V Spasojevic J Alloys Comp 494 52(2010)

45 T Zhang X P Wang and Q F Fang J Phys Chem C 114 11796(2010)

46 A I Shames E Rozenberg M Auslender G GorodetskyC Martin A Maignan and Ya M Mukovskii J Magn MagnMater 290ndash291 910 (2005)

47 P R Sagdeo Sh Anwar and N P Lalla Phys Rev B 74 214118(2006)

48 D Khomskii and K I Kugel Phys Rev B 67 134401 (2003)

Received 30 August 2010 Accepted 14 November 2010



IP 1327286183Wed 26 Oct 2011 112508


higher x8 Let us note that so-called lsquoelectron-hole dopingasymmetryrsquo in the phase diagram of LCMO system9 is evi-dent even from the above schematic and very brief descrip-tion Namely the prevailing ground state in the hole-dopedpart (x lt 05) of this diagram is the FM metallic onewhile the AFMCO insulating ground state dominates inthe electron-doped part (x gt 05)

In this work we consider magnetic ordering in LCMOnanoparticles probed mainly by magnetic resonance tech-nique It is believed that the samplesrsquo size reduction iscapable of influencing the magnetic order in doped man-ganites by eg changing the coupling between the spinsubsystem (both Mn ions and carriers spins) and thelattice1011 Recent magnetic studies of such nanoparti-cles evidence on their well pronounced coreshell spinconfiguration1213 Depending on x the double-exchange(DE) FM interaction occurring via hopping of spin-polarized eg electrons between Mn3+ and Mn4+ ions orAFM superexchange between the t2g + eg local spins ofMn3+ ions34 may prevail in the core The shell whichis in general magnetically and structurally mismatchedwith the bulk-like core may exhibit other eg AFM

E Rozenberg is a Grade A Researcher at the Department of Physics Ben-Gurion Universityof the Negev He got his MSc degree from Ural State University in 1971 and PhD degree inPhysics of Magnetism from Institute of Metal Physics (Ural Branch of Academy of Science)in 1983 both in Sverdlovsk USSR He joined Department of Materials Engineering of BGU(Israel) in 1992 and since 1996 ndash Department of Physics His research interests are focusedon magnetism and electrical transport of solid state

A I Shames is a Senior Researcher in charge of the Laboratory of Magnetic Resonanceat the Department of Physics BGU He received his MSc in Theoretical Physics in 1981from the Kishinev State University Moldova and PhD in Solid State Physics in 1987 fromthe Ural State University Russia In 1992 he joined the Department of Physics BGU Hiscurrent research interests focus on magnetic resonance (ESREPREMR NMR) study ofmanganites and nanocarbons (graphene nanotubes nanodiamonds multishell nanographitesetc) coordination compounds spin labeling in biochemistry and biophysics

M Auslender is a Grade A Researcher and Adjunct Professor at the Department of Elec-trical and Computer Engineering BGU He received his PhD in Solid State Physics in1977 from Institute of Metal Physics at Ural Branch of Academy of Sciences USSR In theend of 1991 he joined the Department of Electrical and Computer Engineering BGU Hiscurrent research interests focus on physics of graphene and manganites diffraction gratingsoptical coherence in regular and disordered media and optical sensors

FM or paramagnetic (PM) spin structures The dc and acmagnetic measurements carried out on optimally doped(x sim 03) LCMO nanoparticles13ndash15 revealed notable sizeeffect on the spontaneous magnetization and Curie tem-perature (TC due to the surface magnetic disorder andinterparticle interactions The same mechanisms were sug-gested to be responsible for spin-glass-like properties ofparticles with the lower x= 0216 The mixed ground statewith AFMCO and FM components characteristic for bulkhalf-doped (x = 05) LCMO transforms to FM-like oneupon sample dimensions reduction717 In a marked con-trast AFMCO or AFMOO ground state appears to be sta-ble upon the size reduction in the electron-doped LCMO(x = 075 and 08)1819

Magnetic resonance technique comprising electronPM (EPR) and FM resonance (FMR) is known asa powerful method for study of temperature struc-tural etc dependences of magnetic interactions Thismethod has been used successively for analysis of mag-neticelectronic state(s) in bulk doped manganites begin-ning from mid nineties20 Note that some attempts toapply electron resonance for study of magneticelectron



IP 1327286183Wed 26 Oct 2011 112508














DIN prop MT HrT

HrT = perpT HrT (1)





IP 1327286183Wed 26 Oct 2011 112508



minus1 = Cminus1

(T minusminus 2

T minus

)(2)





LT =int

0

TtT0TS2

Tdt (4)





LT = H+BT (5)



T minus

)(H

T+B

)(6)









IP 1327286183Wed 26 Oct 2011 112508


200 400 600

2

4

400 600

06

12

300 40000

03

300 400

03

06

400 6000

0

1

400 60000

06

12

200 400 6000

1

2

400 600

08

16

06

(a) Ca01nano

Ca06bulk

(h)

Ca05nano

Ca05bulk

(g)

Temperature T (K)

Ca03nano

(d)

(c)

(b) Ca03bulk

(f)

Ca01bulk

(e)

Ca06nano

Nor

mal

ized

DIN

ndash1




400 600

04

08

12

400 600

04

08

12

400 600

04

08

12

400 600

08

12

400 600

08

12

16

400 600

04

08

200 400 600

04

08

12

16

200 400 600

08

12

Ca03nano

(c)

(b)

Ca05nano

Ca05bulk

Ca06bulk

(h)Ca06nano

(d)

Ca03bulk

Temperature T (K)

Ca01nano

(a)

Ca01bulk

(g)

(f)

(e)

Lin

ewid

th Δ

Hpp

(kG

)








IP 1327286183Wed 26 Oct 2011 112508








i asympminus50



Hs asymp 1454















i asympminus8


s asymp 2407






IP 1327286183Wed 26 Oct 2011 112508


ndash15

00

15

30

ndash30

ndash15

00

15

30

ndash150

ndash75

00

75

150

0 2 4 60 2 4 6ndash10

ndash5

0

5

10

ν = 9434 GHz

(a) T = 240 KT = 2425 K T = 245 K T = 2475 K

ν = 9438 GHz

T = 220 KT = 230 KT = 240 KT = 250 K

240 K

ν = 9463 GHz

(b)

(c)

160 K

240 K

160 K

ν = 9464 GHz

(d)


Res

onan

ce s

pect

ra in

tens

ity (

Arb

Uni

ts)





10

20

30

40

50

20

25

30

35

0 200 400 600

10

20

30

40

50

0 200 400 600

10

20

30

Ca01(a)


Ca03

(c)


Ca05


Temperature T (K)

Ca06


eson

ance

fie

ld

Hr (k

G)




0

100

200

0

100

200

0 200 400 600

0

150

300

0 200 400 60000

25

50

Ca01

Bulk

Nano

(a)

(NI

DT

)K

005(NI

D)

Ca03

(b)

Ca05

(c)

Ca06

(d)

Temperature T (K)




IP 1327286183Wed 26 Oct 2011 112508














IP 1327286183Wed 26 Oct 2011 112508









































IP 1327286183Wed 26 Oct 2011 112508

















IP 1327286183Wed 26 Oct 2011 112508














DIN prop MT HrT

HrT = perpT HrT (1)





IP 1327286183Wed 26 Oct 2011 112508



minus1 = Cminus1

(T minusminus 2

T minus

)(2)





LT =int

0

TtT0TS2

Tdt (4)





LT = H+BT (5)



T minus

)(H

T+B

)(6)









IP 1327286183Wed 26 Oct 2011 112508


200 400 600

2

4

400 600

06

12

300 40000

03

300 400

03

06

400 6000

0

1

400 60000

06

12

200 400 6000

1

2

400 600

08

16

06

(a) Ca01nano

Ca06bulk

(h)

Ca05nano

Ca05bulk

(g)

Temperature T (K)

Ca03nano

(d)

(c)

(b) Ca03bulk

(f)

Ca01bulk

(e)

Ca06nano

Nor

mal

ized

DIN

ndash1




400 600

04

08

12

400 600

04

08

12

400 600

04

08

12

400 600

08

12

400 600

08

12

16

400 600

04

08

200 400 600

04

08

12

16

200 400 600

08

12

Ca03nano

(c)

(b)

Ca05nano

Ca05bulk

Ca06bulk

(h)Ca06nano

(d)

Ca03bulk

Temperature T (K)

Ca01nano

(a)

Ca01bulk

(g)

(f)

(e)

Lin

ewid

th Δ

Hpp

(kG

)








IP 1327286183Wed 26 Oct 2011 112508








i asympminus50



Hs asymp 1454















i asympminus8


s asymp 2407






IP 1327286183Wed 26 Oct 2011 112508


ndash15

00

15

30

ndash30

ndash15

00

15

30

ndash150

ndash75

00

75

150

0 2 4 60 2 4 6ndash10

ndash5

0

5

10

ν = 9434 GHz

(a) T = 240 KT = 2425 K T = 245 K T = 2475 K

ν = 9438 GHz

T = 220 KT = 230 KT = 240 KT = 250 K

240 K

ν = 9463 GHz

(b)

(c)

160 K

240 K

160 K

ν = 9464 GHz

(d)


Res

onan

ce s

pect

ra in

tens

ity (

Arb

Uni

ts)





10

20

30

40

50

20

25

30

35

0 200 400 600

10

20

30

40

50

0 200 400 600

10

20

30

Ca01(a)


Ca03

(c)


Ca05


Temperature T (K)

Ca06


eson

ance

fie

ld

Hr (k

G)




0

100

200

0

100

200

0 200 400 600

0

150

300

0 200 400 60000

25

50

Ca01

Bulk

Nano

(a)

(NI

DT

)K

005(NI

D)

Ca03

(b)

Ca05

(c)

Ca06

(d)

Temperature T (K)




IP 1327286183Wed 26 Oct 2011 112508














IP 1327286183Wed 26 Oct 2011 112508









































IP 1327286183Wed 26 Oct 2011 112508

















IP 1327286183Wed 26 Oct 2011 112508



minus1 = Cminus1

(T minusminus 2

T minus

)(2)





LT =int

0

TtT0TS2

Tdt (4)





LT = H+BT (5)



T minus

)(H

T+B

)(6)









IP 1327286183Wed 26 Oct 2011 112508


200 400 600

2

4

400 600

06

12

300 40000

03

300 400

03

06

400 6000

0

1

400 60000

06

12

200 400 6000

1

2

400 600

08

16

06

(a) Ca01nano

Ca06bulk

(h)

Ca05nano

Ca05bulk

(g)

Temperature T (K)

Ca03nano

(d)

(c)

(b) Ca03bulk

(f)

Ca01bulk

(e)

Ca06nano

Nor

mal

ized

DIN

ndash1




400 600

04

08

12

400 600

04

08

12

400 600

04

08

12

400 600

08

12

400 600

08

12

16

400 600

04

08

200 400 600

04

08

12

16

200 400 600

08

12

Ca03nano

(c)

(b)

Ca05nano

Ca05bulk

Ca06bulk

(h)Ca06nano

(d)

Ca03bulk

Temperature T (K)

Ca01nano

(a)

Ca01bulk

(g)

(f)

(e)

Lin

ewid

th Δ

Hpp

(kG

)








IP 1327286183Wed 26 Oct 2011 112508








i asympminus50



Hs asymp 1454















i asympminus8


s asymp 2407






IP 1327286183Wed 26 Oct 2011 112508


ndash15

00

15

30

ndash30

ndash15

00

15

30

ndash150

ndash75

00

75

150

0 2 4 60 2 4 6ndash10

ndash5

0

5

10

ν = 9434 GHz

(a) T = 240 KT = 2425 K T = 245 K T = 2475 K

ν = 9438 GHz

T = 220 KT = 230 KT = 240 KT = 250 K

240 K

ν = 9463 GHz

(b)

(c)

160 K

240 K

160 K

ν = 9464 GHz

(d)


Res

onan

ce s

pect

ra in

tens

ity (

Arb

Uni

ts)





10

20

30

40

50

20

25

30

35

0 200 400 600

10

20

30

40

50

0 200 400 600

10

20

30

Ca01(a)


Ca03

(c)


Ca05


Temperature T (K)

Ca06


eson

ance

fie

ld

Hr (k

G)




0

100

200

0

100

200

0 200 400 600

0

150

300

0 200 400 60000

25

50

Ca01

Bulk

Nano

(a)

(NI

DT

)K

005(NI

D)

Ca03

(b)

Ca05

(c)

Ca06

(d)

Temperature T (K)




IP 1327286183Wed 26 Oct 2011 112508














IP 1327286183Wed 26 Oct 2011 112508









































IP 1327286183Wed 26 Oct 2011 112508

















IP 1327286183Wed 26 Oct 2011 112508


200 400 600

2

4

400 600

06

12

300 40000

03

300 400

03

06

400 6000

0

1

400 60000

06

12

200 400 6000

1

2

400 600

08

16

06

(a) Ca01nano

Ca06bulk

(h)

Ca05nano

Ca05bulk

(g)

Temperature T (K)

Ca03nano

(d)

(c)

(b) Ca03bulk

(f)

Ca01bulk

(e)

Ca06nano

Nor

mal

ized

DIN

ndash1




400 600

04

08

12

400 600

04

08

12

400 600

04

08

12

400 600

08

12

400 600

08

12

16

400 600

04

08

200 400 600

04

08

12

16

200 400 600

08

12

Ca03nano

(c)

(b)

Ca05nano

Ca05bulk

Ca06bulk

(h)Ca06nano

(d)

Ca03bulk

Temperature T (K)

Ca01nano

(a)

Ca01bulk

(g)

(f)

(e)

Lin

ewid

th Δ

Hpp

(kG

)








IP 1327286183Wed 26 Oct 2011 112508








i asympminus50



Hs asymp 1454















i asympminus8


s asymp 2407






IP 1327286183Wed 26 Oct 2011 112508


ndash15

00

15

30

ndash30

ndash15

00

15

30

ndash150

ndash75

00

75

150

0 2 4 60 2 4 6ndash10

ndash5

0

5

10

ν = 9434 GHz

(a) T = 240 KT = 2425 K T = 245 K T = 2475 K

ν = 9438 GHz

T = 220 KT = 230 KT = 240 KT = 250 K

240 K

ν = 9463 GHz

(b)

(c)

160 K

240 K

160 K

ν = 9464 GHz

(d)


Res

onan

ce s

pect

ra in

tens

ity (

Arb

Uni

ts)





10

20

30

40

50

20

25

30

35

0 200 400 600

10

20

30

40

50

0 200 400 600

10

20

30

Ca01(a)


Ca03

(c)


Ca05


Temperature T (K)

Ca06


eson

ance

fie

ld

Hr (k

G)




0

100

200

0

100

200

0 200 400 600

0

150

300

0 200 400 60000

25

50

Ca01

Bulk

Nano

(a)

(NI

DT

)K

005(NI

D)

Ca03

(b)

Ca05

(c)

Ca06

(d)

Temperature T (K)




IP 1327286183Wed 26 Oct 2011 112508














IP 1327286183Wed 26 Oct 2011 112508









































IP 1327286183Wed 26 Oct 2011 112508

















IP 1327286183Wed 26 Oct 2011 112508








i asympminus50



Hs asymp 1454















i asympminus8


s asymp 2407






IP 1327286183Wed 26 Oct 2011 112508


ndash15

00

15

30

ndash30

ndash15

00

15

30

ndash150

ndash75

00

75

150

0 2 4 60 2 4 6ndash10

ndash5

0

5

10

ν = 9434 GHz

(a) T = 240 KT = 2425 K T = 245 K T = 2475 K

ν = 9438 GHz

T = 220 KT = 230 KT = 240 KT = 250 K

240 K

ν = 9463 GHz

(b)

(c)

160 K

240 K

160 K

ν = 9464 GHz

(d)


Res

onan

ce s

pect

ra in

tens

ity (

Arb

Uni

ts)





10

20

30

40

50

20

25

30

35

0 200 400 600

10

20

30

40

50

0 200 400 600

10

20

30

Ca01(a)


Ca03

(c)


Ca05


Temperature T (K)

Ca06


eson

ance

fie

ld

Hr (k

G)




0

100

200

0

100

200

0 200 400 600

0

150

300

0 200 400 60000

25

50

Ca01

Bulk

Nano

(a)

(NI

DT

)K

005(NI

D)

Ca03

(b)

Ca05

(c)

Ca06

(d)

Temperature T (K)




IP 1327286183Wed 26 Oct 2011 112508














IP 1327286183Wed 26 Oct 2011 112508









































IP 1327286183Wed 26 Oct 2011 112508

















IP 1327286183Wed 26 Oct 2011 112508


ndash15

00

15

30

ndash30

ndash15

00

15

30

ndash150

ndash75

00

75

150

0 2 4 60 2 4 6ndash10

ndash5

0

5

10

ν = 9434 GHz

(a) T = 240 KT = 2425 K T = 245 K T = 2475 K

ν = 9438 GHz

T = 220 KT = 230 KT = 240 KT = 250 K

240 K

ν = 9463 GHz

(b)

(c)

160 K

240 K

160 K

ν = 9464 GHz

(d)


Res

onan

ce s

pect

ra in

tens

ity (

Arb

Uni

ts)





10

20

30

40

50

20

25

30

35

0 200 400 600

10

20

30

40

50

0 200 400 600

10

20

30

Ca01(a)


Ca03

(c)


Ca05


Temperature T (K)

Ca06


eson

ance

fie

ld

Hr (k

G)




0

100

200

0

100

200

0 200 400 600

0

150

300

0 200 400 60000

25

50

Ca01

Bulk

Nano

(a)

(NI

DT

)K

005(NI

D)

Ca03

(b)

Ca05

(c)

Ca06

(d)

Temperature T (K)




IP 1327286183Wed 26 Oct 2011 112508














IP 1327286183Wed 26 Oct 2011 112508









































IP 1327286183Wed 26 Oct 2011 112508

















IP 1327286183Wed 26 Oct 2011 112508














IP 1327286183Wed 26 Oct 2011 112508









































IP 1327286183Wed 26 Oct 2011 112508

















IP 1327286183Wed 26 Oct 2011 112508









































IP 1327286183Wed 26 Oct 2011 112508

















IP 1327286183Wed 26 Oct 2011 112508
















nanometer sized effects on magnetic ordering in la–ca manganites, probed by magnetic resonance

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