Theoretical study of magnetic spin correlations and the magnetocapacitance effect in BiMnO_3

摘要

The magnetic correlations between Mn ion spins and their effects on the magnetocapacitance in BiMnO_3 are studied based on a microscopic model. Above the phase transition temperature of the magnetic subsystem, the magnetic correlations including the longitudinal and transverse parts are nonzero, and they lead to a nonzero specific heat of magnetic subsystem. We show that the magnetocapacitance effect is ascribed to the fluctuation of magnetic correlation. The linear relation between electric susceptibility and the magnetic correlation is obtained and the relevant experiments are explained.