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Probing Electrostructural Coupling on Magnetoelectric CdCr2S4

1IFIMUP and IN- Institute of Nanoscience and Nanotechnology and Department of Physics, University of Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal2CFNUL Center Nuclear Physics, University of Lisbon, Av. Prof. Gama Pinto, 2, 1649-003, Lisboa, Portugal3CICECO and Departament of Physics, University of Aveiro, Campus Universitrio de Santiago, 3810-193 Aveiro, Portugal4ORNL, P.O. Box 2008, MS6475, Oak Ridge, Tennessee 37831-6475, USA5APS - Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA6ITN - Instituto Tecnolgico e Nuclear, EN 10 - Apartado 21, 2686-953 Sacavm, PortugalG.N.P. Oliveira 1,2A.M. Pereira 1J Amaral 3A. M Santos 4T.M Mendona 1Y. Ren 5J.G. Correia 6J.P. Arajo 1A.M.L. Lopes 2Jornadas MAP-fis 2012

OutlineMotivationStructural Details CdCr2S4ResultsStructural CharacterizationMagnetic CharacterizationLocal Atomic Probe CharacterizationElectric Field Gradient PACAtomic displacements PDFConclusions

OutlineMotivationCrystal StructureMacroscopiccharacterizationLocalCharacterizationSummaryOutlineNew solid state systems exhibiting simultaneous (anti) ferroelectric ((A)Fe) and (anti) ferromagnetic ((A)Fm) orders - Multiferroics;[1] S. Lee et al, Nature 451, 805 - 808 (14 Feb 2008)[2] J. Hemberger et al, Nature 434, 364 - 367 (17 Mar 2005)[3] S. Seki et al, Psysical Review Letters 101, 2008Recently, the search for ferroelectricity in materials with known magnetic properties, have already shown some results, namely in:Manganites (RMnO3, R=Gd, Tb, Lu, Y, Er ) [1]Chromites with spinel structure (DCr2X4, D=Cd, Hg, and X= S, Se)[2]Delafossite structure (ABO2, A=Ag, Cu; B=Al,Ga,Cr,... e X=O)[3]Heterostructures (SrTiO3/BiFeO3/CoFe)possibility to manipulate the magnetic degrees of freedom electrically or vice-versa;

Images taken From: N. A. Hill. Why Are There So Few Magnetic Ferroelectrics? The Journal of Physical Chemistry B, 104(29):66946709, 2000.maximization of the (A)Fe-(A)Fm coupling3

Possible applications: new non-volatile memories with magnetic/ electric Read/ Write;OutlineMotivationCrystal StructureMacroscopiccharacterizationLocalCharacterizationSummaryMotivationMy work is based in a motivation that has drawn the attention of many investigators recently, search....Due to this increased attention , the search for has In this kind of compounds network local distortions have a fundamental influence in the ferroelectric and ferromagnetic properties. Thus, for understanding the mechanism inherent to the macroscopic proprieties, local probe studies, for acquiring in+formation about the electronic structure are of the most importance.

3New solid state systems exhibiting simultaneous (anti) ferroelectric ((A)Fe) and (anti) ferromagnetic ((A)Fm) orders - Multiferroics;

[1] S. Lee et al, Nature 451, 805 - 808 (14 Feb 2008)[2] J. Hemberger et al, Nature 434, 364 - 367 (17 Mar 2005)[3] S. Seki et al, Psysical Review Letters 101, 2008possibility to manipulate the magnetic degrees of freedom electrically or vice-versa;Images taken From: N. A. Hill. Why Are There So Few Magnetic Ferroelectrics? The Journal of Physical Chemistry B, 104(29):66946709, 2000.maximization of the (A)Fe-(A)Fm coupling4MotivationPossible applications: new non-volatile memories with magnetic/ electric Read/ Write;

OutlineMotivationCrystal StructureMacroscopiccharacterizationLocalCharacterizationSummaryRecently, the search for ferroelectricity in materials with known magnetic properties, have already shown some results, namely in:Manganites (RMnO3, R=Gd, Tb, Lu, Y, Er ) [1]Chromites with spinel structure (DCr2X4, D=Cd, Hg, and X= S, Se)[2]Delafossite structure (ABO2, A=Ag, Cu; B=Al,Ga,Cr,... e X=O)[3]Heterostructures (SrTiO3/BiFeO3/CoFe)My work is based in a motivation that has drawn the attention of many investigators recently, search....Due to this increased attention , the search for has In this kind of compounds network local distortions have a fundamental influence in the ferroelectric and ferromagnetic properties. Thus, for understanding the mechanism inherent to the macroscopic proprieties, local probe studies, for acquiring in+formation about the electronic structure are of the most importance.

4[1] S. Lee et al, Nature 451, 805 - 808 (14 Feb 2008)[2] J. Hemberger et al, Nature 434, 364 - 367 (17 Mar 2005)[3] S. Seki et al, Psysical Review Letters 101, 2008Recently, the search for ferroelectricity in materials with known magnetic properties, have already shown some results, namely in:Manganites (RMnO3, R=Gd, Tb, Lu, Y, Er ) [1]Chromites with spinel structure (DCr2X4, D=Cd, Hg, and X= S, Se)[2]Delafossite structure (ABO2, A=Ag, Cu; B=Al,Ga,Cr,... e X=O)[3]Images taken From: N. A. Hill. Why Are There So Few Magnetic Ferroelectrics? The Journal of Physical Chemistry B, 104(29):66946709, 2000.5Motivation

OutlineMotivationCrystal StructureMacroscopiccharacterizationLocalCharacterizationSummaryNew solid state systems exhibiting simultaneous (anti) ferroelectric ((A)Fe) and (anti) ferromagnetic ((A)Fm) orders - Multiferroics;

possibility to manipulate the magnetic degrees of freedom electrically or vice-versa;maximization of the (A)Fe-(A)Fm couplingPossible applications: new non-volatile memories with magnetic/ electric Read/ Write;My work is based in a motivation that has drawn the attention of many investigators recently, search....Due to this increased attention , the search for has In this kind of compounds network local distortions have a fundamental influence in the ferroelectric and ferromagnetic properties. Thus, for understanding the mechanism inherent to the macroscopic proprieties, local probe studies, for acquiring in+formation about the electronic structure are of the most importance.

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CrS6CdS4A site Cd2+B site Cr3+- Spinel Family:ACr2X4, A=Cd, Hg, Co, Fe; e X=S, Se, O- Cubic structure: Fd-3m- Cubic Face Centered packing- A Coordenated tetrahedrically- B Coordenated octahedricallyCrystal StructureOutlineMotivationCrystal StructureMacroscopiccharacterizationLocalCharacterizationSummary

Magnetic/Dielectric MeasurementsPhase Transition Para/ferromagneticCurie T -> TC=86 KCurie-Weiss T -> qp=128 KBelow 116 K short-range magnetic clusters H>100 Oe cluster destruition

Inset : Temperature dependence of -1 measured on heating and with H=103 Oe.Graph : -1 as a function of temperature and with different applied magnetic fields (1-101 Oe).

Small increase @ 86K -> above ferroelectric transition Graph: Temperature dependence of complex dielectric constant. The CdCr2S4 sample was measured to a frequency of 500 KHz, 1 and 5 MHz.Relaxor like behavior

OutlineMotivationCrystal StructureMacroscopiccharacterizationLocalCharacterizationSummary8

Short range magnetic cluster (srmc) in the PM regimeLinear correlation between electric and magnetic degrees of freedomMagnetic MeasurementsTheoretical modelLandau Thermodynamic modelOutlineMotivationCrystal StructureMacroscopiccharacterizationLocalCharacterizationSummaryInverse magnetic susceptibility resulting from theoretical calculations of the Landau theory of phase transitions, considering linear magnetoelectric coupling.Hyperfine splitting Source of information

Vzz EFG Main componenth Asymmetry parameterBhf Magnetic hyperfine fieldEFGCdCr2S4111In111CdCr/Cd Site 117Cd117InCd Site Perturbed Angular Correlation (PAC)Probe implanted at ISOLDE/CERN111In and 117Ag isotopesQuadrupolar FrequencyAsymetry ParameterSimilar to:NMR/NQRMESOutlineMotivationCrystal StructureMacroscopiccharacterizationLocalCharacterizationSummary10

Perturbed Angular Correlation (PAC)

2 Local EnvironmentsEFG1 --> Q1=72 MHz and 10.1EFG2 --> Q2=0 MHz (Probe @ Cd cubic site)Representative R(t) functions, correspondent fits and respective Fourier transform.EFG temperature dependence parameters in the CdCr2S4 system, the fraction of each EFG (top), asymmetry parameter (middle) and fundamental frequency (bottom). OutlineMotivationCrystal StructureMacroscopiccharacterizationLocalCharacterizationSummaryPerturbed Angular Correlation (PAC)From 119K to 92K: Dynamic Attenuation is observed (l)Slow thermally activated process

DE=0.1 eVActivation Energy (Ea)

Representative R(t) functions, correspondent fits and respective Fourier transform.OutlineMotivationCrystal StructureMacroscopiccharacterizationLocalCharacterizationSummaryorder-disorder type phase transiction

1050-551015r ()G (-2)

Pair Distribuition Function (PDF)The PDF results at 80 K of the spinel CdCr2S4 structure (blue dots), as a solid red line (fit), with the difference curve (green) offset for clarity. G(r) is the scattering-length weight measure of the apart obtained via Fourier transform of the reduced total scattering structure function.OutlineMotivationCrystal StructureMacroscopiccharacterizationLocalCharacterizationSummary12

1050-551015r ()G (-2)Pair Distribuition Function (PDF)The PDF results at 80 K of the spinel CdCr2S4 structure (blue dots), as a solid red line (fit), with the difference curve (green) offset for clarity. Amplitude of the Cr local off-centering.

The temperature dependence lattice parameter (blue dots) as obtained from Rietveld refinement, the red dashed line is a guide to the eye. The blue dots are the isotropic ADPs for Cr refined from undistorted model. The dashed-line (pink) represents the expected behavior from the Einstein-Debye model. OutlineMotivationCrystal StructureMacroscopiccharacterizationLocalCharacterizationSummaryrmax < 0.011 13OutlineMotivationCrystal StructureMacroscopiccharacterizationLocalCharacterizationSummarySummaryM(T)PACPDFPACe(T)15

VII Jornadas do IFIMUP/IN G.N.P. OliveiraFaculdade de Cincias Universidade do PortoPorto, 19 de Dezembro de 2011Thank You