具有交换偏置的Fe3O4/FeO核/壳纳米材料的简易制备

Facile synthesis of exchange bias effect in core/shell Fe3O4/FeO nanoparticles

Fe3O4在氢氩混合气氛下(10%H2/90%Ar)可以通过一步固相反应法轻微还原生成Fe3O4/FeO核/壳纳米材料,上述结果已经在X线衍射仪、X线光电子能谱、高分辨透射电镜的测量结果中得到验证。Fe3O4/FeO核/壳纳米材料分别受外磁场和零磁场冷至200 K以下时,发现样品受外磁冷下的磁滞回线有明显的向左偏移现象,即交换偏置。另外,纳米材料的交换偏置效应随测试温度升高而减弱,此现象归因于材料界面处的铁磁耦合作用。这种制备方法可能会对其它具有交换偏置现象复合材料的研究提供一种简单有效的实验依据,并有望在交换偏置现象调控方面提供进一步研究。

By slightly reducing in a mixed gas of 10%H2/90%Ar atmosphere with an one-step solid reaction method, Fe3O4 could be transformed into core/shell Fe3O4/FeO nanoparticles(NPs), as confirmed by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and high-resolution transmission electron microscopy(HRTEM). Zero-field and field cooling magnetic hysteresis curves(M-H) exhibited that an obvious exchange bias(shift in the hysteresis loop) could be observed in core/shell Fe3O4/FeO NPs when the measured temperature was below 200 K. However, the exchange bias behavior weakened with increasing temperature, which attributed to the ferromagnetic couplings interaction on the interfaces. Our work may provide a facile and effective experimental strategy for other similar composites with an exchange bias behavior, and provoke further investigations into the manipulation of the exchange bias.