易轴取向对硬磁/软磁多层膜磁性能的影响

The effect of the easy axis orientation on the magnetic properties of hard/soft multilayers

通过微磁学方法,系统计算了硬磁/软磁多层膜(Nd2Fe14B/-Fe多层膜)在晶轴和外场存在夹角情况下的磁矩空间分布、磁滞回线和磁能积.计算表明,在膜面内易轴的偏角对磁性多层膜的磁化反转过程以及剩磁和钉扎场的影响较大.与=0°的情况相比,偏角不为0°时,体系没有明显的成核点.只有在剩磁状态(H=0)时,磁性多层膜内部的磁矩才会出现一致的取向(≡),随着外场的减小,软磁相内部磁矩快速偏转,并且通过界面处的交换耦合作用带动硬磁相内部磁矩的偏转.当软磁相厚度较小时,钉扎场随着的增大先减小后增大,在等于30o附近出现一个低谷;当软磁相厚度较大时,钉扎场随着的增大而单调增大.体系的剩磁和矫顽力随着的增加都呈现出减小的趋势,导致磁能积随的增加而急剧减小,这在一定程度上解释了材料最大磁能积的实验值和理论值之间的巨大差距.

Magnetization distributions, hysteresis loops and energy products have been calculated systematically for a hard/soft multilayer system with a deviation of easy axis β taken into account, where β is the angle between the easy axis and the applied field. The calculations show that the deviation of the easy axis β affects the reversal process of the magnetization, the remanence as well as the pinning field significantly. When β≠0°, there is no obvious nucleation point in contrast with the case of β=0°. Magnetizations in the multilayer system orient at the same direction （θ≡β） only at the remanence state （H=0）. When the applied field H decreases, the magnetization of the soft phase deviate rapidly and drives the magnetization in the hard phase by the exchange-coupling at the interface. The pinning field has a peak for small Ls and increases monotonously for large Ls when increases. Both remanence and coercivity decreases as β increases, leading to a sharp decrease of the energy product, which partially explained the large difference between the experimental and theoretical energy products.