Low-Temperature Magnetic and Dielectric Anomalies in Rare-Earth-Substituted BiFeO_3 Ceramics

摘要

In this work, we report on the magnetic and dielectric anomalies observed in dense Bi_(1-x)RE_xFeO_3 ceramics (RE = Dy, Tb; 0 ≤ x ≤ 0.3) at cryogenic temperatures. For compositions with a high content of rare-earth ions, thermomagnetic experiments revealed a distinct anomaly in the magnetization curves at temperatures below 200 K. The temperature of the magnetic anomaly along with a thermal hysteresis was found to be dependent on the rare-earth concentration and magnetic field strength. Low-temperature dielectric measurements showed an anomalous relaxor-like behavior of the relative permittivity and dielectric loss in highly doped ceramic samples. The anomalies in low-temperature magnetization and dielectric response are suggested to result from the presence of GdFeO_3-like orthoferrite phase and/or bismuth rare-earth-mixed iron garnet impurities.