外场取向对铁磁/反铁磁双层膜交换偏置的影响

Influence of orientation angle of external field on the exchange bias of ferromagnetic/antiferromagnetic bilayer films

利用斯通纳-沃尔法斯(Stoner-Wohlfarth,SW)模型详细讨论了铁磁/反铁磁双层膜交换偏置对外场取向角的依赖关系。解析推导出转换场和矫顽力的表达式。用两种办法计算了交换偏置场(he)和磁滞回线的半宽度(HWHL),结果分别用(he)s、(HWHL)s和(he)c、(HWHL)c表示。计算表明,(he)s、(HWHL)s和(he)c、(HWHL)c有很大区别,而只有(he)s和(HWHL)s显示出明显的阶跃现象。我们的结果还说明,转换角方程的奇点是阶跃现象的根源。另外,能量曲线的局域极小不是阶跃现象产生的必要条件。

The angular dependence of exchange bias for ferromagnetic/antiferromaguetic bilayers has been investigated in detail with the help of the Stoner-Wohlfarth model. The equations for determining the switching field and the expressions of coercivity were obtained analytically. We present two approaches to calculate the exchange bias field （he） and the half width of the hysteresis loop （HWHL）, and distinct the results as （he）s, （HWHL）s and （he）c, （HWHL）c, respectively. The results indicated that only （he）s and （HWHL）s show obvious jump phenomenon. And it was found that, the singularity in the equation to determine the switching angle, i.e., the critical angle at which the magnetization flips, is the origin of the jump phenomenon. It was also indicated that the local minimum of the energy landscape is not a necessary condition for occurring of jump phenomenon.