Larger polarization and weak ferromagnetism in quenched BiFeO3 ceramics with a distorted rhombohedral crystal structure

Single-phase insulating BiFeO3 ceramics have been synthesized by a simple but effective method that conventional solid state reaction is followed immediately by quenching processing. At room temperature, the ceramics show a metastable, distorted rhombohedral phase and the refined structure parameters are presented based on x-ray diffraction. It is revealed that the formations of Fe2+ and oxygen deficiency are greatly suppressed by the quenching processing. A well-saturated ferroelectric hysteresis loop with a large remnant polarization (2Pr=23.5μC∕cm2) is observed with an applied field of 155kV∕cm. Temperature-dependent magnetic property is investigated and weak ferromagnetism with a remnant magnetization of 4×10−6μB∕Fe at 10K is established. These results may have implications for further studies on multiferroics.