Anomalous Behavior in Temperature Dependence of Pyroelectric Polarization and Magnetoelectric Polarization of Magnetite below 60 K

抄録

An electric polarization which contains spontaneous electric polarization and magnetoelectric polarization of magnetite was measured over a temperature range from 4.2 K to 60 K. The observed electric polarization is divided into two parts: one is due to rotation of magnetization and the other is independent of it. An anomalous behavior in temperature dependence was observed in both of these two parts at the same temperature of 6 K. In earlier reports, anomalous behaviors in pyroelectric polarization and in magnetoelectric polarization were measured individually at this temperature. Another anomaly was observed at about 45 K, which was interpreted as an effect due to the switching of the a axis to the b axis by the magnetic field. A change caused by breaking of the mirror symmetry was not observed at about 10 K in the present measurements.