Fe_3O_4纳米颗粒的磁性研究

The study on the magnetic properties of nano-grain Fe_3O_4

测量了Fe3O4纳米颗粒的零场冷却(ZFC)和加场冷却(FC)时的磁化强度随温度的变化关系,以及不同温度下的磁滞回线(Loop)。用Preisach模型对测量数据进行了拟合,其中主要考虑热涨落和自由能壁垒随温度的变化,数值模拟结果再现了Fe3O4纳米颗粒的各种磁化强度的变化规律。又对拟合得到的巴克豪森跳跃谱的有关参数进行讨论,讨论结果在纳米颗粒表现出的超顺磁性上给出了一定的理论指导。

<Abstrcat>A sample of nano-grain Fe_3O_4 was synthesized using coprecipitation. It was characterized by zero field cooling (ZFC) and field cooling (FC) magnetic moments and the major hysteresis loops. The data have been analyzed within the framework of a generalized Preisach model, which includes thermal fluctuations, critical phenomenon, and the temperature dependent distribution of free energy barriers. The model provides an excellent description of the experimental data, and the simulated results are in good agreement with experiment results. All the ZFC/FC curves at different applied fields and all the major hysteresis loops at different temperatures can be replicated by the model with one set of parameters, and the parameters have been discussed, the discussion results shows some guidance in theory about supermagnetic properties of nanograins.