硬、软磁多层膜体系成核的解析分析

我们运用微磁学方法，解析地推导了交换耦合多层膜的成核场公式，得到了成核场分别随软、硬磁相厚度变化的曲线，并给出了成核时磁矩角度的空间分布．我们发现成核场随软磁相厚度L^s增加而单调减小，随硬磁相厚度L^h增加而单调增加，没有出现一些文献中所发现的平台和峰值．当L^h〉5nm时，L^h对成核场的影响可以忽略，L^s对成核场起主导作用．成核点磁矩分布并不唯一，但角度满足一定的比值关系．随着薄膜厚度（主要是L^s）的减小，软、硬磁间交换耦合作用逐渐增强，复合磁体由退耦合磁体逐步过渡到交换弹簧，并最后过渡到刚性磁体．即使是刚性磁体，也不会出现完全一致转动的成核模式．

Analysis of the nucleation in hard/soft magnetic multilayers

The formulae for nucleation fields have been derived analytically within a micromagnetic model for an exchange coupled multilayers, with the curves of the nucleation fields and the spatial distributions of the magnetic moments obtained as functions of the soft and hard layer thicknesses. It is found that the nucleation field decreases uniformly as the soft layer thickness L^s increases while it increases as the hard layer thickness Lh increases. The platform and peaks as found in some literatures don＇t occur in our results. When L^h〉 5 nm, the effect of the L^h on the nucleation field could be ignored and the nucleation field is dominated by the L^s. At the nucleation, the distribution of the magnetic moment is not unique, however, the angular ratios satisfy some certain equations. As the thickness of the films （mainly L^s） decreases, the coupling between the soft and hard layers is enhanced. In the meantime, the composite magnet changes gradually from the decoupled magnet to the exchanges spring, and finally to the rigid composite one. The totally coherent rotation can not occur, even for the rigid composite magnet.