journal of magnetism and magnetic materials 369 (2014) 9-13

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Magnetoelectric coupling effect in transition metal modi edpolycrystalline BiFeO 3 thin lmsVenkata Sreeniva s Puli a ,b ,n , Dhire n Kumar Pradhan b , Sreenivasulu Golla pudi c ,Indrani Coondoo d , Neeraj Panwar e , Shiva Adireddy a , Douglas B. Chrisey a , Ram S. Katiyar ba Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118, USAb Department of Physics and Institute of Functional Nanomaterials, University of Puerto Rico, San Juan, PR 00936, USAc Department of Physics, Oakland University, Rochester, MI 48309-4401, USAd Department of Materials and Ceramic & CICECO, University of Aveiro, 3810-193 Aveiro, Portugale Department of Physics, Central University of Rajasthan, Bandar Sindri, Kishangarh 305801, Rajasthan, India

a r t i c l e i n f o

Article history:Received 22 January 2014Received in revised form11 May 2014Available online 12 June 2014

Keywords:MultiferroicMagnetoelectric couplingDielectric propertiesPLDTransition metalBiFeO3

a b s t r a c t

Rare-earth (Sm) and transition metal (Co) modi ed polycrystalline BiFeO 3 (BFO) thin lms have beendeposited on Pt/TiO 2 /SiO2 /Si substrate successfully through pulsed laser deposition (PLD) technique.Piezoelectric, leakage current and temperature dependent dielectric and magnetic behaviour wereinvestigated for the lms. Typical butter y-shaped loop were observed in BSFCO lms with aneffective piezoelectric constant ( d33 ) 94 pm/V at 0.6 MV/cm. High dielectric constant 900 and lowdielectric loss 0.25 were observed at room temperature. M H loops have shown relatively highsaturation magnetization 35 emu/cm 3 at a maximum eld of H 20 kOe. Enhanced magnetoelectriccoupling response is observed under applied magnetic eld. The multiferroic, piezoelectric, leakagecurrent behaviours were explored. Such studies should be helpful in designing multiferroic materialsbased on BSFCO lms.

& 2014 Elsevier B.V. All rights reserved.

1. Introduction

Multiferroic magnetoelectric materials with the coexistence of at least two ferroic orders (ferroelectric, ferromagnetic and ferro-elastic, ferrotoroidic) and exhibiting coupling between them havedrawn ever-increasing attention in the last decade due to theirpotential for applications in multifunctional devices. Such materi-als are rare in nature since they require simultaneously showferroelectric (empty d-orbitals) and ferromagnetic ( lled transi-tion metal d-orbitals) properties which are mutually exclusive [1] .BiFeO3 (BFO) is a room temperature, natural single phase perovs-kite multiferroic material, exhibiting ferroelectricity and antiferro-magnetism with, ferroelectric Curie temperature ( T C ) 1100 K,

and Neel temperature ( T N ) 643 K [1]. It has a rhombohedraldistorted ABO 3 type perovskite structure with R3c symmetry atroom temperature. With such speci c features that both T C and T N in BFO are above room temperature and can be tailored orconverted to ferromagnetic state with proper substitution, BFO

nds great technological applications e.g. four-state memorydevices [1]. Nevertheless, its spontaneous polarization and

saturation magnetization are comparatively lower than manystandard ferroelectrics and ferromagnets. Various researchershave worked to investigate the effects of doping/substitution onthe physical properties of BiFeO 3 . For example, Bernardo et al. [2]synthesized Ti-doped BiFeO 3 ceramics by a mixed-oxide route andobserved an enhancement in the dc resistivity and magneticbehaviour with Ti-substitution. Pradhan et al. prepared polycrys-talline samples of Bi 0.9 La0.1 Fe1 xMn xO3 by a conventional solid-state reaction technique [3] .

The dielectric constant, loss tangent and magnetization valuesincrease with increasing of Mn concentration. Panwar et al.reported thin lms of Bi 1 xPr xFe1 yCo yO3 via chemical solutiondeposition method, wherein the co-substituted lm exhibited the

lowest leakage current density and enhanced magnetic (M

Hcurves) behaviour [1]. This is attributed to the superimpositionof a spiral spin structure on BFO s antiferromagnetic order. More-over, its ferroelectric and transport properties are degraded byhigh leakage currents making it dif cult to pole the sample athigher electric elds.

In BFO, ferroelectric and transport properties are also hinderedby leakage problems, which arise as a result of defects, nonstoi-chiometry, and low resistivity (high leakage current) [4]. Reduc-tion in leakage current and hence the ensuing increase in theelectrical resistivity and the ferroelectric behaviour can beachieved by proper substitution at either Bi/Fe-sites individually

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Journal of Magnetism and Magnetic Materials

http://dx.doi.org/10.1016/j.jmmm.2014.05.0500304-8853/ & 2014 Elsevier B.V. All rights reserved.

n Corresponding author at: Department of Physics and Engineering Physics,Tulane University, New Orleans, LA 70118, USA. Tel.: 1 239 537 4964;fax: 1 504 862 8702.

E-mail addresses: [email protected] , [email protected] (V. Sreenivas Puli).

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or at both the sites simultaneously that results in elimination of impurities phases and oxygen vacancies.

Improved multiferroic properties can be achieved to someextent by introducing suitable dopant ions in this material. A orB site substitution in BFO can lead to reduction in leakage currentand increase in resistivity by eliminating secondary impurities andoxygen vacancies, thereby improving its ferroelectric properties.

Yang et al. synthesized Bi 1 xLa xFe1 yCo yO3 polycrystalline thin

lms on Pt/TiO 2 /SiO2 /Si substrate via chemical solution depositionmethod [4]. The dielectric constant of the co-doped lm was nearlytwo times higher than that of pristine BFO lm while the dielectricloss was smaller than 0.07. They also reported the enhancedsaturation magnetization in the co-doped lm. Zhu et al. grewMn-doped BiFeO 3 (BFMO) thin lms on SrTiO 3 (0 0 1) substratewith a bottom electrode of SrRuO 3 [5] . Hu et al. [6] fabricated Ndand Mo co-doped BNFM thin lms on platinised silicon substrate bypulsed laser deposition (PLD) technique. The ferroelectric andferromagnetic properties were signi cantly enhanced by Nd andMo co-doping of the BFO lm. Enhanced ferroelectric, piezoelectricproperties were reported for W 6 substituted at Fe 3 in BiFe1 xW xO3 lms [7]. Enhanced dielectric, ferroelectric and anti-fatigueproperties were observed by Yu et al., in La 3 and V 5

co-substitued Ba0.85

La0.15

Fe1 x

V xO

3 (BLFV) ceramics [8]. Leakage

current density of BLFV ceramics was several orders of magnitudelower than individual substitution, La 3 at Bi3 site or V 5 at Fe 3

site in BFO lattice [8]. Low leakage current behavior was alsoobserved in La 3 and Ni 2 co-substituted BFO thin lms [9].As well enhanced physical properties was also reported by Chenget al. in La 3 and Nb 5 co-substituted BFO lms [10] .

Low dielectric dissipation factor, leakage current density andimproved ferromagnetism with fatigue-free behaviour wasobserved in Nd 3 /Mo 6 co-substituted BFO samples [11] , andCe3 /Zr 4 co-substituted BFO samples [12] . Improved magneticbehavior with exchange bias effect was observed in La 3 , Zr4

co-substituted BFO lms [13] . Suppressed leakage current densitybehaviour was observed in (Pr 3 , Mn4 ) co-substituted BFO thin

lms in the high electric eld region [14] . Improved magnetization

and large piezoelectric response was observed in Co substitutedBFO lms [15] . Enhanced piezoelectric coef cient ( d33 ) wasobserved in (1 x)BiFeO3 xBiCoO3 solid solution [16] . Superiordielectric and ferroelectric properties were reported in Tb, Crco-substituted BFO chemical solution deposited lms [17] . Besidesthe improvement in the electric and magnetic properties, therecan also occur structural transition with substation in BFOsamples. For example, Kan et al. reported a structural transitionfrom the rhombohedral to an orthorhombic phase accompaniedby a double hysteresis polarization loop in (Bi,Sm)(Fe,Sc)O 3co-doped thin lms [18] . Similar behaviour was also observed forco-substituted Bi 0.9 Sm0.1 Fe1 xMn xO3 system by Stefan et al. [19] .Zhai et al. also reported structural transition in La 3 at Bi3 site orNb5 at Fe 3 site in BFO lattice [20] .

In this work, Sm and Co co-substituted polycrystallineBi0.9 Sm 0.1 Fe0.95 Co0.05 O3 (BSFCO) thin lms have been grown byPLD technique and studied for their electrical, dielectric andmagnetoelectric properties. Other studies including x-ray diffrac-tion (XRD), atomic force microscopy (AFM), photovoltaic responseand piezoresponse force microscopy (PFM) on the same lms haverecently been reported elsewhere [21] .

2 4 6 8 10 12 14 16

BiBiPt

PtBi

BiPt

Bi

Pt

Bi

Bi PtPtCo

CoFe

Sm

FeSm

SmSmTiTi

Bi

PtBi

BiSi

SmPt

OFeCo

Element Weigh t% Atomic%

O K 17.00 60.79Si K 0.82 1.67

Ti K 0.14 0.17

Fe K 17.69 18.12

Co K 1.14 1.11

Sm L 6.21 2.36

Pt L 9.15 2.68

Bi L 47.84 13.10

Totals 100.00

I n t e n s

i t y

( a .

u . )

Energy (KeV)

Ti

Fig. 1. (a) Scanning electron microscopy (SEM) (b) electron diffraction spectroscopy (EDAX) patterns and (c) elemental mapping of Bi 0.9 Sm 0.1 Fe0.95 Co0.05 O3 (BSFCO) thin lms.

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2. Experimental procedure

Ceramic target of Bi 0.9 Sm0.1 Fe0.95 Co0.05 O3 (BSFCO) were synthe-sized by a sol gel synthesis as described elsewhere [22] . Polycrys-talline multiferroic BSFCO thin lms of thickness from 300 to360 nm were grown from these targets by pulsed laser deposition(PLD) on Pt/TiO 2 /SiO2 /Si substrate in a temperature range of 700 750 1 C, under an oxygen partial pressure of 100 mTorr, annealed for

30 min and were subsequently cooled to room temperature in300 Torr oxygen partial pressure. An excimer laser (KrF, 248 nm)with a laser energy density of 2 5 J/cm 2 , pulse repetition rate of 10 Hz with a substrate target distance of 4 5 cm, was used for lmgrowth. Test structures were fabricated by sputtering Pt to createtop electrodes with 200 mm diameters at room temperature.Dielectric properties, ferroelectric hysteresis (P V) loops wereobtained at 4 kHz and leakage current measurements were doneunder vacuum (10 4 Torr) with HP4294A impedance analyzer andRadiant Precision Multiferroic materials Analyzer respectively. Thetemperature control was achieved using a programmable tempera-ture controller (MMR Technologies, Inc.). The d33 measurement wascarried out with MTI-2100 Fotonic Sensor connected to radiantferroelectric tester. In order to characterize the magnetic propertiesof the lms, a vibrating sample magnetometer (VSM, Lakeshore,Model 7300 series) was used.

3. Results and discussion

3.1. Surface morphology

The surface morphology of BSFCO thin lm system wasobserved by SEM is displayed in Fig. 1(a). The SEM micrographs

of lm have shown uniform distribution of grains throughout thesurface of the sample. The grains and grain boundaries are wellde ned in the sample. Dense homogeneous microstructures withminimum number of voids were observed in SEM micrographs.Dense microstructure in the BSFCO system is attributed suitableannealing temperature of the PLD deposited lms. The averagegrain size of BSFCO lms is about 50 nm as shown in the gure.Grain growth in these lms might be due to higher annealing

temperature 700 1

C. Energy dispersive spectroscopy (EDX) mea-surement and atomic wt% of each element present in the lmswere tabled ( Fig. 1(b)) and elementary mapping images of Bi, Fe,Sm, Co, and O, respectively, captured by SEM-EDX ( Fig. 1(c)) showsall the elemental peaks of BSFCO along with peaks correspondingto Pt/TiO 2 /SiO2 /Si substrate. From the SEM micrograph ( Fig. 1(a)),BSFCO lms did not show any obvious agglomeration.

3.2. Multiferroic and leakage current properties

The electric polarization vs. applied electric eld (P E loops) forBSFCO lm is shown in Fig. 2(a). The BSFCO lm has unsaturatedferroelectric characteristics: the remnant polarization (Pr), satura-tion polarization (Ps), and coercive eld (Ec) at a maximumapplied eld of 0.8 MV/cm were 16.06 mC/cm 2 , 22.91 mC/cm 2 ,and 0.48 MV/cm, respectively. It should be noted that BSFCO lmshow leaky ferroelectric properties due to the comparatively highconductivity. In general pristine BFO lms exhibit poor ferro-electric properties due to high leakage current behavior, howeverin contrast, Indrani et al. [15] , reported that chemical solutiondeposited BiFe 0.95 Co0.05 O3 lms have shown low leakage currentwith improved polarization and is caused by Co 3 substitutionand suppression of Fe 2 ions at BiFeO 3 lattice and they also

-1.0 -0.5 0.0 0.5 1.0-30

-20

-10

0

10

20

30

E(MV/cm)

3V

5V

6V

8V

15V

18V

20V

25V

30V

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-100

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d 3 3

( p m

/ V )

E(MV/cm)-0.2 -0.1 0.0 0.1 0.2

10 -1110 -1010 -910 -810 -710 -610 -510 -4

C u r r e n

t D e n s

i t y

( A / c m

2 )

E(MV/cm)

P ( C / c m

2 )

Fig. 2. (a) Polarization-electric eld hysteresis loops at 4 kHz frequency of Bi 0.9 Sm 0.1 Fe0.95 Co0.05 O3 (BSFCO) thin lm; (b) leakage current density (J E) behavior and

(c) Electric eld dependent piezoelectric coef cient ( d33 ) of Bi0.9 Sm 0.1 Fe0.95 Co0.05 O3 (BSFCO) thin lms.

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3.4. Temperature dependent dielectric properties

The dielectric properties as a function of temperature for BFSCOlm is shown in Fig. 4 It is evident that the dielectric constant

decreases with increasing frequency indicating the signature of polar dielectrics. As the temperature increase dielectric peakbroadening is observed around 350 450 K up to 1 kHz. The BSFCOsamples show decreasing trends of their dielectric constant anddielectric loss values on increasing frequency, at higher frequencyregion dielectric constant value remains almost remains constantabove 100 Hz frequency. The observed dielectric behavior has beenexplained on the basis of dipole relaxation phenomenon whereinat low frequencies the dipoles are able to follow the frequency of the applied eld relaxation wherein at low frequencies the dipolesare able to follow the frequency of the applied eld [28] . Howeverdielectric loss is moderately low and there is no consistency in thedielectric loss behavior at different temperature measured. Thehigh dielectric constant at lower frequency might be attributed tothe oxygen vacancies, piling of interfacial dislocations, grainboundary effect and the decrease in dielectric constant withincreasing frequency is due to the difference in the contributionsof different polarization mechanisms [29,30] . As shown in Fig. 4,low dielectric loss values at high frequencies might be due todiploes with small effective mass (electrons and ferroelectricdomains mainly) [31] . High dielectric loss in high temperatureregion is attributed to space charge polarization [32] .

4. Conclusions

In conclusion we have studied the effect of co-substitution onBiFeO3 lms on its multiferroic, piezoelectric, leakage current

behavior, magnetoelectric coupling and dielectric properties.M H loops show that the present lms have relatively high saturationmagnetization 35 emu/cm 3 at a maximum eld of H 20 kOe.Enhance mangetoelectric coupling ( E with H to a maximum of 500 mV/cm Oe) behavior was witnessed in the BSFCO lms. A notablepiezoelectric constant of approximately 94 pm/V was found; this isclose to values obtained for PZT lms.

Acknowledgements

This work was supported by the DOD Grant no. W911NF-11-1-0204. Acknowledgment is also due to DOE Grant no. FG02-08ER46526 for providing nancial support to the student DhirenK. Pradhan and to NSF-EFRI RESTOR no. 1038272 Grant forsupporting Dr. Venkata S. Puli.

References

[1] Neeraj Panwar, Indrani Coondoo, Amit Tomar, A.L. Kholkin, Venkata S. Puli,Ram S. Katiyar, Mater. Res. Bull. 47 (2012) 4240 4245 .

[2] M.S. Bernardo, T. Jardiel, M. Peiteado, F.J. Mompean, M. Garcia-Hernandez,M.A. Garcia, M. Villegas, A.C. Caballero, Chem. Mater. 25 (2013) 1533 1541 .

[3] D.K. Pradhan, R.N.P. Choudhary, C. Rinaldi, R.S. Katiyar, J. Appl. Phys. 106(2009) 024102 .

[4] K.G. Yang, Y.L. Zhang, S.H. Yang, B. Wang, J. Appl. Phys. 107 (2010) 124109 .[5] X.H. Zhu, H. Ba, M. Bibes, S. Fusil, K. Bouzehouane, E. Jacquet, A. Barthlmy,

D. Lebeugle, M. Viret, D. Colson, Appl. Phys. Lett. 93 (2008) 082902 .[6] Zhongqiang Hu, Meiya Li, Benfang Yu, Ling Pei, Jun Liu, Jing Wang,

Xingzhong Zhao, J. Phys. D: Appl. Phys. 42 (2009) 185010 .[7] Ling Cheng, Guangda Hu, Bo Jiang, Changhong Yang, Weibing Wu, Suhua Fan,

Appl. Phys. Exp. 3 (2010) 101501 .[8] B. Yu, M. Li, J. Wang, L. Pei, D. Guo, X. Zhao, J. Phys. D: Appl. Phys. 41 (2008)

185401 .[9] S.K. Singh, K. Maruyama, H. Ishiwara, Appl. Phys. Lett. 91 (2007) 112913 .

[10] Z. Cheng, X. Wang, S. Dou, H. Kimura, K. Ozawa, Phys. Rev. B: Condens. Matter77 (2008) 092101 .

[11] Z. Hu, M. Li, B. Yu, L. Pei, J. Liu, J. Wang, X. Zhao, J. Phys. D: Appl. Phys. 42 (2009)185010 .

[12] J. Liu, M. Li, Z. Hu, L. Pei, J. Wang, X. Liu, X. Zhao, Appl. Phys. A 102 (2011) 713.

[13] C. Lan, Y. Jiang, S. Yang, J. Mater. Sci. 46 (2011) 734 .[14] T. Kawae, Y. Terauchi, T. Nakajima, S. Okamura, A. Morimoto, J. Ceram. Soc. Jpn.118 (2010) 652 .

[15] Indrani Coondoo, Neeraj Panwar, Amit Tomar, Igor Bdikin, A.L. Kholkin,Venkata S. Puli, Ram S. Katiyar, Thin Solid Films 520 (21) (2012) 6493 6498 .

[16] Y. Nakamura, M. Kawai, M. Azuma, M. Kubota, M. Shimada, T. Aiba,Y. Shimakawa, J. Appl. Phys. 50 (2011) 031505 .

[17] Guohua Dong, Guoqiang Tan, Wenlong Liu, Ao Xia, Huijun Ren, J. Mater. Sci.:Mater. Electron. (2013) , http://dx.doi.org/10.1007/s10854-013-1636-x .

[18] D. Kan, R. Suchoski, S. Fujino, I. Takeuchi, Int. Ferroelectr. 111 (1) (2010)116 124 .

[19] Stefan Saxin, Christopher S. Knee, Dalton Trans. 40 (2011) 3462 3465 .[20] L. Zhai, Y.G. Shi, S.L. Tang, L.Y. Lv, Y.W. Du, J. Phys. D: Appl. Phys. 42 (2009)

165004 .[21] Venkata Sreenivas Puli, Dhiren Kumar Pradhan, Rajesh Kumar Katiyar,

Indrani Coondoo, Neeraj Panwar, Pankaj Misra, Douglas B. Chrisey, J.F. Scott,Ram S. Katiyar, J. Phys. D: Appl. Phys. 47 (2014) .

[22] Venkata Sreenivas Puli, Ashok Kumar, N. Panwar, I.C. Panwar, Ram S. Katiyar, J. Alloys Compd. 509 (32) (2011) 8223 8227 .

[23] Dean J.A. Lange s, Handbook of Chemistry, 15th ed., McGraw-Hill, New York,1999 .

[24] S.T. Zhang, Y. Zhang, M.H. Lu, C.L. Du, Y.F. Chen, Z.G. Liu, Y.Y. Zhu, N.B. Ming,X.Q. Pan, Appl. Phys. Lett. 88 (2006) 162901 .

[25] G.L. Yuan, S.W. Or, J.M. Liu, Z.G. Liu, Appl. Phys. Lett. 89 (2006) 052905 .[26] D.H. Wang, W.C. Goh, M. Ning, C.K. Ong, Appl. Phys. Lett. 88 (2006) 212907 .[27] G.L. Song, H.X. Zhang, T.X. Wang, H. GYang, F.G. Chang, J. Magn. Magn. Mater.

324 (2012) 2121 2126 .[28] D.H. Wang, W.C. Goh, M. Ning, C.K. Ong, Appl. Phys. Lett. 88 (21) (2006)

212907 212909 .[29] Reetu, Ashish Agarwal, Sujata Sanghi, Ashima, Neetu Ahlawat, Monica, J. Appl.

Phys. 111 (2012) 113917 .[30] Venkata Sreenivas Puli, Dhiren K. Pradhan, Douglas B. Chrisey, M. Tomozawa,

J.F. Scott, G.L. Sharma, Ram S. Katiyar, J. Mater. Sci. 48 (2013) 2151 2157 .[31] Samita Pattanayak, R.N.P. Choudhary, Piyush R. Das, Electron. Mater. Lett.

(2013) , http://dx.doi.org/10.1007/s13391-013-3050-1 .[32] B.K. Barick, K.K. Mishra, A.K. Arora, R.N.P. Choudhary, Dillip K. Pradhan, J. Phys.

D: Appl. Phys. 44 (2010) 355402 .

300 350 400 450 500

0

200400

600

800

1000

1200

D i e l e c

t r i c C o n s

t a n

t

T(K)

100Hz

1kHz

10kHz

100kHz

1MHz

300 350 400 450 5000.00

0.25

0.50

0.75

1.00

T(K)

100Hz

1kHz

10kHz

100kHz

1MHz

D i e l e c

t r i c

l o s s

( t a n

)

Fig. 4. Temperature dependent dielectric properties for Bi 0.9 Sm 0.1 Fe0.95 Co0.05 O3(BSCFO) thin lms.

V. Sreenivas Puli et al. / Journal of Magnetism and Magnetic Materials 369 (2014) 9 13 13
http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref1http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref1http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref1http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref1http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref1http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref2http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref2http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref2http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref2http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref2http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref3http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref3http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref3http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref4http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref4http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref5http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref5http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref5http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref6http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref6http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref6http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref7http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref7http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref7http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref8http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref8http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref8http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref9http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref9http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref10http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref10http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref10http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref11http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref11http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref11http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref12http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref12http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref13http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref13http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref14http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref14http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref14http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref15http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref15http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref15http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref15http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref15http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref16http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref16http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref16http://dx.doi.org/10.1007/s10854-013-1636-xhttp://refhub.elsevier.com/S0304-8853(14)00525-3/sbref18http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref18http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref18http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref18http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref18http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref19http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref19http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref19http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref19http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref20http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref20http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref20http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref21http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref21http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref21http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref21http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref22http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref22http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref22http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref22http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref22http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref23http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref23http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref23http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref23http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref23http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref24http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref24http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref24http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref25http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref25http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref26http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref26http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref27http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref27http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref27http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref27http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref27http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref28http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref28http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref28http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref28http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref28http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref29http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref29http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref29http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref30http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref30http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref30http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref30http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref30http://dx.doi.org/10.1007/s13391-013-3050-1http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref32http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref32http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref32http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref32http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref32http://dx.doi.org/10.1007/s13391-013-3050-1http://dx.doi.org/10.1007/s13391-013-3050-1http://dx.doi.org/10.1007/s13391-013-3050-1http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref30http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref30http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref29http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref29http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref28http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref28http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref27http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref27http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref26http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref25http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref24http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref24http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref23http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref23http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref22http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref22http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref21http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref21http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref21http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref20http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref20http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref19http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref18http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref18http://dx.doi.org/10.1007/s10854-013-1636-xhttp://dx.doi.org/10.1007/s10854-013-1636-xhttp://dx.doi.org/10.1007/s10854-013-1636-xhttp://refhub.elsevier.com/S0304-8853(14)00525-3/sbref16http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref16http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref15http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref15http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref14http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref14http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref13http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref12http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref11http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref11http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref10http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref10http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref9http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref8http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref8http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref7http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref7http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref6http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref6http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref5http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref5http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref4http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref3http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref3http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref2http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref2http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref1http://refhub.elsevier.com/S0304-8853(14)00525-3/sbref1

journal of magnetism and magnetic materials 369 (2014) 9-13

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