Ferroelectricity in Spiral Magnets

Abstract

It was recently observed that materials showing most striking multiferroic phenomena are frustrated spin-density-wave magnets. We present a simple phenomenological theory, which describes the orientation of the induced electric polarization for various incommensurate magnetic states, its dependence on temperature and magnetic field, and anomalies of dielectric susceptibility at magnetic transitions. We show that electric polarization can be induced at domain walls and that magnetic vortices carry electric charge.

Magneto-optical study of the spin-polarized electronic states in multiferroicTbMnO3

“…Below T F , the inversion symmetry of the lattice is broken by the bc-cycloidal arrangement of the spins, inducing a ferroelectric polarization along the c axis while the antiferromagnetic ordering along the b axis persists. 3,4,6 Here, we study the coupling between spin and charge degrees of freedom in multiferroic TbMnO 3 by examining the temperature-dependent dielectric responses xx and xy , which are the diagonal and off-diagonal components of the dielectric tensor. The magnetization of a material breaks the symmetry between left and right circularly polarized ͑LCP and RCP͒ light.…”

“…The close coupling of the magnetization and the electric polarization in multiferroics makes these materials excellent candidates for demonstrating giant magnetoelectrical behavior, 1,2 in which large magnetic and electric responses can be induced with weak electric and magnetic fields, respectively. 3,4 Spectral generalized magneto-optical ellipsometry ͑SGME͒ is an ideal technique for studying the interplay between electric and magnetic properties in multiferroic systems, as it probes both the diagonal xx and off-diagonal xy components of the dielectric tensor. 5 Multiferroicity in TbMnO 3 is induced by spin-charge coupling.…”

Thermodynamic properties of LiCu2O2 multiferroic compound

“…According to the observation of the low temperature magnetic structure, Sato et al [10,11] have confirmed that the relation P ∝Q × e 3 holds in LiCu 2 O 2 compound, where P , Q and e 3 are the ferroelectric polarization, the modulation vector and the helical axis of the ordered spins. This indicates that the theories derived by phenomenological [29] and microscopic models [30][31][32] are also applied for polarization of LiCu 2 O 2 . Thus, according to the spin current model, or equivalently, the inverse Dzyaloshinskii-Moriya interaction, P i induced by the neighboring canting spins (S i and S j ) is expressed as follows:…”

Canted magnetic ground state of quarter-doped manganitesR0.75Ca0.25MnO3(R = Y, Tb, Dy, Ho, and Er)

“…[1][2][3][4][5][6][7][8][9] This includes studies of Type-I multiferroics employing materials such as the hexagonal YMnO 3 where ferroelectricity and magnetism have different origins, 10 and also studies of Type-II multiferroics as in the cases of TbMnO 3 and orthorhombic HoMnO 3 where the ferroelectricity is caused by peculiar magnetic orders. [11][12][13] All of these multiferroic RMnO 3 materials are located in the narrowbandwidth limit of manganites due to their small R 3+ ionic size.…”