CoFe₂O₄/CoFe₂ nanocomposites with exchange coupling behavior have been obtained from a two-step process. First, CoFe₂O₄ nanoparticles with size of 11 nm were synthesized using a co-precipitation method. And second, the as-synthesized CoFe₂O₄ nanoparticles were reduced under mixed gas (Ar 95% + H₂ 5%) for 1 h at different temperatures. The structure, phase, particle size, morphology, and magnetic properties with the reduction temperature were studied. X-ray diffraction and Mössbauer spectroscopy results show the whole process from pure CoFe₂O₄ hard magnetic phase to pure CoFe₂ soft magnetic phase when the reduction temperature increases from 400 to 700 °C, and CoFe₂O₄/CoFe₂ hard/soft nanocomposites are obtained at 500 and 600 °C. Magnetic measurement result show there is a stronger exchange coupling interaction between CoFe₂O₄ and CoFe₂ for the sample reduced at 500 °C, but not in the sample reduced at 600 °C. A giant 76% enhancement of the maximum magnetic energy product (BH)_max compared with pure CoFe₂O₄ will be of technological significance in the future.

通过两步法获得了具有交换偶联行为的CoFe ₂ O ₄ / CoFe ₂纳米复合材料。首先，使用共沉淀法合成尺寸为11 nm的CoFe ₂ O ₄纳米颗粒。其次，在混合气体（Ar 95％+ H ₂ 5％）下于不同温度下将合成后的CoFe ₂ O ₄纳米颗粒还原1 h。研究了还原温度下的结构，相，粒度，形貌和磁性。X射线衍射和Mössbauer光谱结果表明，从纯CoFe ₂ O ₄硬磁相到纯CoFe的整个过程当还原温度从400℃升高到700℃时，获得₂软磁相，并在500和600℃下获得CoFe ₂ O ₄ / CoFe ₂硬/软纳米复合材料。磁测量结果表明，在500°C下还原的样品中CoFe ₂ O ₄和CoFe ₂之间存在更强的交换耦合相互作用，而在600°C下还原的样品中则没有。与纯CoFe ₂ O ₄相比，最大磁能积（BH）_max大幅提高76％具有未来的技术意义。