Effects of magnetic correlation on the electric properties in multiferroic materials

The effects of magnetic correlation on the electric properties in the multiferroic materials are studied, where the phase transition temperature of the magnetic subsystem Tm is lower than that of the electric subsystem Te. A Heisenberg-type Hamiltonian and a transverse Ising model are employed to describe the ferromagnetic and ferroelectric subsystems, respectively. We find that the magnetic correlation can influence the electric properties above the Tm, and magnetic transverse and longitudinal correlations have opposite functions. In the curves of temperature dependence of polarization, kinks appear at Tm which is dominated by the sharp change of decreasing rate of the magnetic correlation. The kinks can be eliminated by an external magnetic field. The magnetic transverse and longitudinal correlations play contrary roles on the manipulation of polarization by the external magnetic field.