The study of the coupling mechanism between antiferromagnetic and ferroelectric ordering and thermodynamic properties in ferroelectromagnets

We study the coupling mechanism between antiferromagnetic and ferroelectric ordering that coexist spontaneously at low temperatures. According to the results of experiment and previous theoretical. considerations, we propose a possible coupling form related to a combination of electric polar and spin correlation and use it to calculate the thermodynamic properties of a ferroelectromagnetic system, including, its magnetization m, polarization p, magnetization susceptibility chi(m), magnetoclectric susceptibility chi(me) and polarization susceptibility chip, in the case of magnetization m perpendicular to polarization p. It is found that the relationship between m, chi(m) and chi(me) Is in agreement with. that of phenomenological theory, and polarization induced by magnetic coupling leads to an anomaly of chi(p) at low temperature, which is consistent qualitatively with experimental results.