Binary nanoparticles composed of BiFeO₃ and Bi₂Fe₄O₉ have attracted considerable interest due to their magnetic properties and exchange bias effect. In this paper, two samples of well-crystallized BiFeO₃/Bi₂Fe₄O₉ binary nanoparticles with varying compositions, containing approximately 3 % and 32 % of the Bi₂Fe₄O₉ crystalline phase, were investigated to understand the impact of microstructural variations on the magnetic behavior of the samples. Both BiFeO₃ and Bi₂Fe₄O₉ phases of binary nanoparticles were synthesized in the same synthesis process by calcining amorphous precursors obtained after solvent evaporation from aqueous solutions containing iron and bismuth nitrates and tartaric acid. The identification and quantification of crystalline phases of the produced samples were performed using the X-ray diffraction technique and multiphase Rietveld refinement, respectively. The structure and microstructures of the synthesized BiFeO₃/Bi₂Fe₄O₉ nanoparticles were carried out using transmission electron microscopy techniques. The atomic composition of the samples was investigated by energy-dispersive X-ray. The magnetic properties were studied by the DC magnetization technique. Transmission electron microscopy analyses showed that both samples exhibit a bimodal particle size distribution, with average particle sizes of ∼ 116 nm and ∼ 6.5 nm for the ∼ 3 % Bi₂Fe₄O₉ sample. In contrast, for the ∼ 32 % Bi₂Fe₄O₉ sample the average particle sizes were ∼ 108 nm and ∼ 7 nm, respectively. Energy-dispersive X-ray analyses revealed a Fe-rich impurity phase in both samples. Temperature-dependent zero-field-cooled and field-cooled magnetization curves present a large separation between them below 300 K and zero-field-cooled curves are consistent with a broad (bimodal) size distribution of the nanoparticles for both samples. Magnetic hysteresis loops measured at 5 K after the samples are cooled from 400 K in a zero magnetic field show weak ferromagnetism for the ∼ 3 % Bi₂Fe₄O₉ sample, whereas the ∼ 32 % Bi₂Fe₄O₉ sample presents an improved ferromagnetism. An exchange bias-type effect was observed in both samples. The results suggest that the increase of ultrasmall Bi₂Fe₄O₉ nanoparticles leads to an improvement in the coercivity and remanence of BiFeO₃/Bi₂Fe₄O₉ binary nanoparticles.

_{由BiFeO 3}和Bi ₂ Fe ₄ O ₉组成的二元纳米颗粒由于其磁性和交换偏压效应而引起了人们的广泛关注。在本文中，研究了两个具有不同成分的结晶良好的 BiFeO ₃ /Bi ₂ Fe ₄ O ₉二元纳米粒子样品，分别含有大约 3 % 和 32 % 的 Bi ₂ Fe ₄ O ₉晶相，以了解样品磁性行为的微观结构变化。BiFeO ₃和Bi ₂ Fe ₄ O ₉相的二元纳米粒子是在相同的合成过程中通过煅烧从含有铁、硝酸铋和酒石酸的水溶液中蒸发溶剂获得的无定形前体来合成的。分别使用 X 射线衍射技术和多相 Rietveld 精修对所生产的样品的晶相进行鉴定和定量。使用透射电子显微镜技术对_{合成的BiFeO 3} /Bi ₂ Fe ₄ O _{9纳米粒子}的结构和微观结构进行了研究。通过能量色散 X 射线研究样品的原子组成。通过直流磁化技术研究了磁性能。透射电子显微镜分析表明，两个样品均呈现双峰粒度分布，其中~3% Bi ₂ Fe ₄ O ₉样品的平均粒度为~ 116 nm 和~ 6.5 nm。相比之下，对于约 32% Bi ₂ Fe ₄ O ₉样品，平均粒径分别为约 108 nm 和约 7 nm。能量色散 X 射线分析表明，两个样品中均存在富铁杂质相。温度相关的零场冷却和场冷却磁化曲线在低于 300 K 时呈现出较大的分离，并且零场冷却曲线与两个样品的纳米颗粒的宽（双峰）尺寸分布一致。样品在零磁场中从 400 K 冷却后在 5 K 处测量的磁滞回线显示，~ 3 % Bi ₂ Fe ₄ O ₉样品具有弱铁磁性，而 ∼ 32 % Bi ₂ Fe ₄ O _{9样品则显示出弱铁磁性。}样品呈现出改进的铁磁性。在两个样本中都观察到了交换偏倚型效应。结果表明，超小型Bi ₂ Fe ₄ O _{9纳米颗粒的增加导致BiFeO 3} /Bi ₂ Fe ₄ O ₉二元纳米颗粒的矫顽力和剩磁提高。