铁磁体/绝缘体(半导体)/铁磁体型隧道结中的层间交换耦合

Interlayer Exchange Coupling in Ferromagnet/Insulator(Semiconductor)/Ferromagnet Tunnel Junction

基于自由电子模型,本文研究了由非金属中间层隔开的两铁磁体之间的层间交换耦合。其中特别注意到了铁磁层厚度dFM 及费密面随磁化排列的变化对层间耦合的影响。结果发现:(1)dFM 的变化会导致层间交换耦合(IEC)出现两种不同的特征,一种是随着中间层厚度的增加,IEC有振荡行为;另一种是其指数衰减行为;(2)作为dFM 的振荡函数,IEC表现出多个周期和一个负的非振荡项;(3)传导电子的费密能会随着两铁磁体的磁化排列变化而稍有变化,进一步地,这种变化与IEC有着某种程度的关联。

Interlayer exchange coupling(IEC)between two ferromagnets(FMs) separated by a nonmetallic spacer is analyzed theoretically within the free electron approximation.Particular attention is paid to the influence of FM thickness d FM on IEC and the variation of Fermi energy with the magnetization alignment of two FMs.It is found that:(1) the variation of d FM may lead to two different features for the IEC,one is the oscillatory behavior of IEC with the spacer thickness,the other is the exponential behavior in the most spacer thickness.(2)As a oscillatory function of d FM ,the IEC exhibits multiple periods and a negative non oscillatory term.(3)The Fermi energy of the conduction electrons has a little variation as the magnetization of the two FMs changes from parallel to antiparallel alignment,furthermore,this variation is correlated with the IEC to some extent.