不同压制压力下NiFe_2O_4纳米固体的ESR研究

THE PREPARATION AND ELECTRON SPIN RESONANCE STUDY OF NiFe 2O 4 NANOSOLIDS UNDER HIGH PRESSURE

以反滴共沉定法制备了ＮｉＦｅ２Ｏ４纳米微粉，并在不同压力下将其压制成纳成米固体，然后用ＸＲＤ谱和ＥＳＲ谱研究了ＮｉＦｅ２ｏ４纳米固体结构和界百状态随压制压力的变化。实验结果表明，ＮｉＦｅ２ｏ４纳米固体的结构在高压下没有明显的变化，但其ＥＳＲ谱的共振线宽和ｇ因子值随着压力升高均表示出先逐渐增大至最大值，然手缓慢下降的规律。这种变化可以归因于纳米固体内部界面离子间的磁相互作用在压力的下所发生和变化。这引起实验结果境示，对于ＮｉＦｅ２ｏ４纳米固体而言，最佳的成型压力是４．５ＧＰａ，在此压力下，ＮｉＦｅ２ｏ４纳米粒子既可以被压制成致密的纳米固体。

In the present paper, the NiFe 2O 4 nanoparticles which were synthesized by the method of reserve drop coprecipitation,then compacted into nanosolids under different pressures. The variation of structure and interfacial states in NiFe 2O 4 nanosolids under different pressrues are studied by XRD and ESR measurement for the first time. The experimental results indicate that, the structure of nanosolids has not changed obviously under the pressure up to 6 0GPa; but the linewidth and g factor values of their ESR spectra would increase significantly with increasing pressure up to 4 5GPa and then turn to decrease under higher pressures. These variations could be interpreted by the change of magnetic interaction in the NiFe 2O 4 nanosolids under different pressures. These experimental results suggest that 4 5GPa is the best forming pressure, under which the NiFe 2O 4 nanoparticles can be compacted into densest solid but their structure and nano properties have not been destroyed.