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LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS

LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS. A. M. Lima Lopes , V. S. Amaral, J. G. Correia, J. P. Araújo, E. Rita, T. M. Mendonça, J. S. Amaral, A. Pereira, M. Reis, F. Figueiras, A. Marques, M.R Silva, P.B. Tavares, Y. Tomioka, Y. Tokura

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LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS

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  1. LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS A. M. Lima Lopes, V. S. Amaral, J. G. Correia, J. P. Araújo, E. Rita, T. M. Mendonça, J. S. Amaral, A. Pereira, M. Reis, F. Figueiras, A. Marques, M.R Silva, P.B. Tavares, Y. Tomioka, Y. Tokura Is390 collaboration

  2. LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS • Materials • Experimental results in Pr1‑XCaXMnO3 • Preliminary results in multiferroic systems • Conclusions OUTLINE

  3. Mn3+ O2- Pr3+ R3+1-xCa2+xMn3+1-xMn4+xO3 Dopingwith Divalent ions(Ca, Sr…) Mn3+/Mn4+MIX-VALENCE No JT effect Control Mn-Odistances • Overlap betweenMn& O orbitals • Magnetic & electric properties Y Mn-O-Mnangle (y<180o) LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS Mn3+3d4 Cubic perovskite Jahn-Teller effect eg RMnO3 D - crystal field R O t2g Mn MANGANITES • Octahedra distortion • Cation misfitstructure distorts

  4. RHOMBOHEDRIC ORTHORHOMBIC FERROMAGNETIC METALLIC FERROMAGNETIC INSULATOR CHARGE ORDER Cheong et al, Physica B, 318, 39 (2002) ANTIFERROMAGNETIC INSULATOR LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS Strong coupling ofSPIN,CHARGE,ORBITAL andLATTICE RICH PHASE DIAGRAM Mn3+/Mn4+ localization in a ordered way What is the nature of the CHARGE ORDERstates? E. Dagotto, Open questions in CMR manganites…, New Journal of Physics, 7, 67 (2005) What is hidden behind the CHARGE ORDERstates?

  5. Sharp resistivity increase Magnetization decrease CO Resistivity (Wcm) Y. Tokura et al., PRB, 64, (2001)195133 High Magnetic Field -- Melting of CO LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS Pr1-xCaxMnO3 Charge Order for a large range of compositions Pr1-xCaxMnO3 mag/elect phase diagram CO/OO signatures

  6. FM dimers Mn3+-O-Mn3+ coupled AF (Zener polarons) Adapted M. Coey, Nature 430, 155 (2004) Charge contrast Small CC No CC Hybridization Grenier et al, Phys Rev. B 69, 134419 (2004) Daoud-Aladine et al, Phys Rev. Lett 89, 97205 (2002) P. G. Radaelli et all. Phys. Rev.B 55, 3015 (1997) LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS Charge and Orbital Order Classical picture Mn3+/ Mn4+ Arrays • FM Zig-Zag chains • coupled AF

  7. Inversion symmetry is broken + = Wigner crystal Site centered CO Zener polaron bond centered CO Ferroelectricity LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS New scenario for the Charge Ordered State Theoretical work predicted the possibility of local electric dipole moments in CO manganites D.Efremov et al, Nature Materials, 3,853 (2004) CO state in Pr1-xCaxMnO3 New paradigm for ferroelectricsbut… Till now there is no experimental prove that electric polarization exists in CO Pr1-xCaxMnO3

  8. Ei g1 L1 |Ii, mi〉 DE = e.Q.Vzz (m2-m’2)/4I(2I-1) m , Q t h= (Vxx-Vyy)/Vzz E DE |I, m〉 . ÑEQ g2 Bhfm Ä L2 DE = mBhf =hwL(m-m`) |If, mf 〉 Ef EFGsensitive to small changes in the electronic structure PAC sensitive tool to probe local electric ordering LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS Local probe: Perturbed Angular Correlation Hyperfine splitting Source of information Magnetic hyperfine field/Electric field gradient Probe nuclear moments Vzz- EFG principal component h- Asymmetry parameter Bhf- Magnetic hyperfine field Samples implanted with 111mCd (t1/2= 85ns, Q=0.83 b, m=-0.766 mn, I=5/2) Cd @ Pr/Ca site

  9. LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS Pr1-xCaxMnO3 PAC anisotropy functions Measured for ≠ Ca (x) content Measured at several temperatures @ RT X=0.25 x=0 292 K x=0.25 250 K x=0.50 200 K x=1 132 K

  10. Samples without CO Samples with CO T** X=0.25 X=0.40 X=0.35 TCO Vzz increases with decreasing T T** CO region CO region X=0.85 @ RT @ RT CO region Softening of vibration modes EFG Sensitive to the lattice dynamics LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS Vzz @ h Room temperature Anomalous Vzz (T) dependence

  11. x=0.40 x=0.35 Pr0.65Ca0.35MnO3 TCO T* TCO d ~ 18%d ~32% x=0.85 TCO T* T* TCO T* LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS Charge order region Vzz as a function of temperature PAC anisotropy functions x=0.35 • Sharp increase of Vzz @ T< TCO • Dropping at T* from 85 to 67 Vzz/Å-2 in 2 K

  12. LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS Correlation between EFG and magnetic susceptibility X=0.40 X=0.85 X=035 1/ 1/ 1/ 1/ T* TCO T* TCO T* TCO

  13. TC LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS From NMR and PAC studies in Ferroelectrics EFG  sensitive to local electric dipoles Y. Yeshurun et al, J. Phys. & Chem. Solids 40 231 (1979) Divergence Electric Susceptibility Local Spontaneous Polarization

  14. Landau Theory: first order phase transitions X=0.35 X=0.40 X=0.85 T0 Tc T<Tc T>Tc Data compatible with first-order dielectric phase transition below Tco LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS Fitting the data … To model Vzz(T) … Electric susceptibility / spontaneous polarization below TC

  15. Theoretical prediction D.Efremov et al, Nature Materials, 3,853 (2004) PPr~1mC/m2 LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS Spontaneous Polarization PbHfO3 DVzz/Vzz~0,03 DVzz/Vzz~7,6 Y. Yeshurun et al, J. Phys. & Chem. Solids 40 231 (1979) PPr~PHf/15 Fist observation of polarization in CO Manganites New mechanism for ferroelectricity PHf~10mC/m2 PPr~0.7mC/m2

  16. Hexagonal phase Trigonal bipyramid LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS MATERIALS WITH SIMULTANEOUS ELECTRIC AND MAGNETIC ORDER AMnO3Multiferroic Manganites Orthorrombic phases octahedra Adapted from: Van Aken , thesis univ. Groningen

  17. 100K EuMnO3 ErMnO3 10K ErMnO3 LuMnO3 AMnO3Multiferroic Manganites Measurements in GdMnO3, HoMnO3,YMnO3 … at several temperatures 10K 10K

  18. LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS • The charge order transition is driven by the softening of vibration modes • Experimental evidence for coexistence of electric and magnetic order in charge ordered Pr1-xCaxMnO3 system • The dielectric phase transition is of first-order • Polar state appears below the charge order temperature • Promising PAC results in multiferroicEuMnO3, ErMnO3… Conclusions

  19. LOCAL PROBING OF ELECTRIC AND MAGNETIC ORDER COEXISTENCE IN MANGANITE SYSTEMS ISOLDE Collaboration V.S. Amaral, J.C. Amaral, M. S. Reis CICECO, Univ. Aveiro J.P. Araújo, T.M. Mendonça, A. Pereira IFIMUP, Univ. Porto J. G. Correia, E. Rita, A. Marques,M.R Silva ITN, Sacavém P.B. Tavares UTAD, Vila Real W.Tröger, T. Butz Fakultät für Physik und Geowissenschaften, Univ. Leipzig Y. Tomioka, Y. Tokura Joint Research Center for Atom Technology, Tsukuba R. Suryanarayanan Lab. Physico-Chimie de l’etat Solide, Univ. Paris-Sud Thanks

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