小尺寸正方形铁磁薄膜边界效应对磁化翻转过程的影响

用自旋动力学方法系统地研究磁偶极相互作用表现的边界效应对小尺寸正方形铁磁薄膜的磁化翻转过程的影响.在确定的磁偶极相互作用强度下,针对不同的单轴各向异性强度和不同的磁化角(外磁场与易轴间的夹角),具体给出矫顽场与磁化角及单轴各向异性强度之间的依赖关系和-些有代表性的磁滞回线,并给出磁化翻转过程中-些有代表性的微观磁结构.模拟结果表明:磁偶极相互作用表现的边界钉扎作用与单轴各向异性场之间的竞争决定磁滞回线的形状和矫顽场的大小,从而在不同磁化角情况下会导致不同的矫顽场机理.本文提出可有效地描述正方形铁磁性薄膜复杂微观磁畴结构的形成与演变的五磁畴模型.这种五磁畴模型既能直接揭示单轴各向异性正方形铁磁薄膜的几何特性和物理特性,也方便于磁化翻转过程的分析.

Boundary Effects in Magnetization Reversal of Micro-square Ferromagnetic Thin Films

Boundary effects in magnetization reversal induced by dipole-dipole interaction in micro-square ferromagnetic films are studied by means of spin dynamics simulation.Fixing strength of dipole-dipole interaction,coercive force is calculated as functions of strength of uniaxial anisotropy and magnetization angle θ(the angle between applied field and easy axis).Typical hysteresis loops and spin configurations are given.It shows that shape of hysteresis loop and magnitude of coercive force are determined by a competition between boundary pinning effect and uniaxial anisotropic field,which leads to different coercivity mechanism under different θ.An effective five-magnetic-domain model is proposed to describe spin configurations of square ferromagnetic thin films.The model shows conveniently geometric and physical properties of square ferromagnetic thin films with uniaxial anisotropy as well as its magnetization reversal process.