Electric polarization induced by phase separation in magnetically ordered and paramagnetic states of RMn2O5 (R=Gd, Bi)

Abstract

The electric polarization hysteresis loops and remanent polarization were revealed in multiferroics RMn${}_2$O${}_5$ with $R=Gd$ and $Bi$ at wide temperature interval from 5 K up to 330 K. Until recently, the long-range ferroelectric order having an exchange-striction magnetic nature had been observed in RMn${}_2$O${}_5$ only at low temperatures ($T\le T_C=30$ -- 35 K). We believe that the polarization we observed was caused by the frozen superparaelectric state which was formed by the restricted polar domains resulting from phase separation and charge carriers self-organization. At some sufficiently high temperatures $T\gg T_C$ the frozen superparaelectric state was destroyed, and the conventional superparaelectric state occurred. This happened when the potential barriers of the restricted polar domain reorientations become equal to the kinetic energy of the itinerant electrons (leakage). The hysteresis loops were measured by the so-called PUND method which allowed us to correctly subtract the contribution of conductivity from the measured polarization. The correlations between properties of the phase separation domains and polarization were revealed and studied. The high-temperature polarization also had a magnetic nature and was controlled by the magnetic field because the double exchange between pairs of Mn ions with different valences (Mn${}^{3+}$ and Mn${}^{4+}$) in RMn${}_2$O${}_5$ was the basic interaction resulting in phase separation.

10 pages, 9 figures

References in corpus (5)

• Spin current and magneto-electric effect in non-collinear magnets
• A Neutron diffraction study of multiferroics RMn2O5
• Superparaelectric phase in the ensemble of non-interacting ferroelectric nanoparticles
• Phase diagram for Coulomb-frustrated phase separation in systems with negative short-range compressibility
• Coarse grained models in Coulomb-frustrated phase separation

Cited by in corpus (6)

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• Magnetic Dynamics of Phase Separation Domains in GdMn2O5 and Gd0.8Ce0.2Mn2O5 Multiferroics
• Electric Polarization in ErCrO3 Induced by Restricted Polar Domains
• Effect of Rare-Earth Ions on an Electric Polarization Induced by the Phase Separation Domains in RMn2O5 (R = Er, Tb)
• Effect of the Optical Pumping and Magnetic Field on the States of Phase Separation Domains in Eu_{0.8}Cr_{0.2}Mn_2O_5
• Frustration of Exchange-Striction Ferroelectric Ordering and Growth of Electric Polarization of Phase Separation Domains in R${}_{0.8}$Ce${}_{0.2}$Mn${}_2$O${}_5$ (R = Er, Tb) Solid Solutions