磁性多层膜磁特性的表面效应

利用Monte-Carlo方法和转移矩阵法研究了具有不同表面交换耦合J_s和薄膜厚度 磁性多层 膜的表面和尺寸对磁相变的影响.模拟结果表明，系统的相变温度随薄膜层数的变化取决于J_s/J(J为体内交换耦合)，当J_s/J大于某一临界值时，由于表面磁 有序先于体内磁有序 ，系统的相变温度随薄膜层数的增多而降低，反之，表面磁无序可与体内磁有序共存，系统 的相变温度随薄膜层数的增多而升高；当J_s/J较小时，随J_s增大 ，系统的居里温度缓慢 升高，趋近于体内相变温度，而当J_s/J较大时，随J_s增大，系统的 居里温度 呈线性升高.模拟结果与用转移矩阵法推导出的结果相当符合，且很好地解释了实验事实. 关键词： 磁星多层膜 交换耦合 Monte-Carlo模拟 转移矩阵法

Monter-Carlo simulation of surface magnetism of multilayered films

Based on the Monte-Carlo simulation, the effects of both the ratio of surface interaction to bulk one J_s/J and the multilayered thickness on the cri tical beh avior are studied. It is found that whether the phase transition temperature inc reases with increasing number of multilayers depends on the value of J_{s/J. Whe n the value of Js/J is above a certain critical value, the system bec omes orde red in the surface before it gets in order in the bulk. Below this critical valu e, one can find that a magnetically disordered surface can coexist with a magnet ically ordered bulk phase. For a small Js/J, the transition temperatu re increa ses slowly with the increase of Js/J and finally are equal to the transiti on temperature of the bulk. When Js/J is large enough, the transition temperat ure increases linearly with the increase of Js/J.The simulated result s are con sistent with those derived by the mean field theory with the transfer matrix met hod, and well explain the experimental facts.}