The multiferroic properties of BiFeO3-Na0.5Bi0.5TiO3 solid solution ceramics

Summary form only given. Solid solutions of BiFeO₃ with other ABO₃ materials such as Na_0.5Bi_0.5TiO₃ (NBT) have been found to effectively improve the ferromagnetic and ferroelectric properties [1, 2]. However, till now, the study on electrical control of magnetization is still lacking. Solid solutions of 80% BFO and 20% NBT (BFO-NBT), 80% Bi_0.95La_0.05FeO₃ and 20% NBT(BLFO-NBT) have been prepared. The magnetic properties were investigated by a Physical Property Measurement System, and further by a commercial vector vibrating sample magnetometer for magnetic moment parallel and perpendicular to the field direction. X-ray diffraction patterns show the polycrystalline R3c structure, and 5% La doping has little influence on the structure. The polarization-electric field hysteresis loops confirm the ferroelectricity of both samples. Fig.1 shows the M-H curves measured at 300 K. Clear ferromagnetic hysteresis loops are observed for both samples, consistent with previous reports [1, 2]. Similar M-H loops with comparable magnetization for BFO-NBT and BLFO-NBT confirm our previous results that 5% La doping has little influence on the magnetic properties of BFO [3]. With poling field of 55 kV/cm applied on both samples for half an hour, the magnetization of BFO-NBT was strongly suppressed (from 0.726 emu/g to 0.282 emu/g at 60 kOe), while that of BLFO-NBT was nearly unchanged. The drop of magnetization in poled BFO-NBT was measured to be mainly due to the decrease of parallel component (parallel to magnetic field), while perpendicular component (perpendicular to magnetic field) was nearly unchanged. The re-orientation of magnetization for the poled BFO-NBT can been excluded. The enhanced magnetization in BFO-NBT has been attributed to the defect configurations like oxygen vacancies or vacancy ion centers [1]. The strongly suppressed magnetization in poled BFO-NBT might be attributed to the - edistribution of oxygen vacancies under electric field, leading to the decrease of defect configurations. The mobility of oxygen vacancies was weakened by 5% La substitution, hindering the redistribution of oxygen vacancies.