Abstract The pure single phase BiFeO3 nanoparticles have been prepared by microwave-assisted sol-gel process and its structure and magnetic properties have been studied. X-ray diffractometer, infrared and transmission electron microscope results show that the synthesized BiFeO3 nanoparticles at the calcining temperature of 450 °C exhibits a rhombohedrally distorted perovskite structure without secondary phase and the size is about 40 nm. Meanwhile, the pure single phase BiFeO3 particles exhibit typical ferromagnetic properties at room temperature and the obvious large exchange bias phenomenon at 60 K. A exchange bias field (HE) of 302 Oe at 60 K for pure single phase BiFeO3 nanoparticles at calcining temperature 450 °C after field cooling at 20 KOe has been observed. The MT curve at H = 100 Oe shows that the FC and ZFC magnetization curves start to differ in the temperature range from 60 K to 300 K revealing spin glass behavior of BiFeO3 nanoparticles at calcining temperature 450 °C, 500 °C and 550 °C. The ferromagnetic behavior is attributed to size of effects, which partially destroy the long-wavelength cycloid spin structure expected in bulk BiFeO3. The exchange bias effect in single crystalline BiFeO3 nanoparticles arises from co-existence of different magnetic phases of an antiferromagnetic core and a ferromagnetic surface. The ferromagnetic, exchange bias effect and spin glass behavior of BiFeO3 nanoparticles are assigned to the uncompensated or canted spins at the ferromagnetic surface and an antiferromagnetic core of BiFeO3 nanoparticles.

中文翻译：

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微波辅助溶胶-凝胶法制备纯单相BiFeO 3 纳米颗粒的结构和磁性能

摘要 采用微波辅助溶胶-凝胶法制备了纯单相BiFeO3纳米颗粒，并对其结构和磁性能进行了研究。X射线衍射仪、红外和透射电镜结果表明，合成的BiFeO3纳米颗粒在450℃的煅烧温度下呈现菱形畸变钙钛矿结构，无二次相，尺寸约为40 nm。同时，纯单相 BiFeO3 颗粒在室温下表现出典型的铁磁性，在 60 K 时表现出明显的大交换偏压现象。纯单相 BiFeO3 纳米颗粒在 450° 煅烧温度下的 60 K 时交换偏压场（HE）为 302 Oe已经观察到在 20 KOe 场冷却后的 C。H = 100 Oe 时的 MT 曲线表明 FC 和 ZFC 磁化曲线在 60 K 到 300 K 的温度范围内开始不同，揭示了 BiFeO3 纳米颗粒在 450 °C、500 °C 和 550 °C 煅烧温度下的自旋玻璃行为. 铁磁行为归因于效应的大小，这部分地破坏了块状 BiFeO3 中预期的长波长摆线自旋结构。单晶 BiFeO3 纳米粒子中的交换偏置效应源于反铁磁芯和铁磁表面的不同磁相的共存。BiFeO3 纳米颗粒的铁磁、交换偏置效应和自旋玻璃行为归因于铁磁表面的未补偿或倾斜自旋和 BiFeO3 纳米颗粒的反铁磁核。