微扰场下Ni纳米圆环磁结构的微磁学研究

以微磁学理论为基础，采用三维动力学模型研究了Ni纳米铁磁圆环的微磁结构与体系结构参数的关系，以预测纳米铁磁圆环体系的磁特性。结果表明：在内外半径比一定的条件下，外半径较小时，体系的磁结构只是单一的“一致”态；外半径较大时，磁结构不仅有“蜗旋”态和“洋葱”态，而且出现马蹄”态以及特殊“洋葱”态。并对各种磁结构的反转形式以及反转速度进行了研究；在反磁化过程中，对于“一致”态、“蜗旋”态以及特殊“洋葱”态磁结构，体系磁矩基本是沿厚度方向变化；而“洋葱”态磁结构，则沿三维空间变化（但始终保持磁矩在膜面内的分量基本不变）。另外，随外半径增大，“蜗旋”态磁结构的反转时间变化微弱；“洋葱”态的反转时间迅速缩短；“马蹄”态随外半径增大，开关时间明显缩短。并对结果进行了定性的解释。

A Micromagnetic Study of Magnetization Configuration of Ni Nano-ring in Perturbation Field

To forecast the magnetism of the Ni nano-ring, the relation between the micromagnetic configuration and structure parameter of this system is investigated by using three-dimension dynamic model based on micromagnetie theory. The results show that to fixed inner-outer radius ratio, for small outer radius, the magnetization configuration is ＂consistent＂ state. But for biggish one, the magnetization configurations include not only ＂vortex＂ and ＂onion＂ states but also the ＂horseshoe＂ and the special ＂onion＂ states.In the course of reversal magnetization,for the ＂consistent＂, ＂vortex＂ and special ＂onion＂ states, the magnetic moment move basically along the thickness direction. However, for the ＂onion＂ state,the magnetic moment changes along the three-dimensional space,maintaining the magnetic moment in the film plane is basically unchanged. Besides, the reversal time of the ＂vortex＂ state is basically unchanged and that of the ＂onion＂ state and the switch time of the ＂horseshoe＂ state shorten rapidly.