磁性超晶格中的非线性体静磁波

Nonlinear bulk magnetorstatic waves in magnetic superlattices

利用等效介质理论,研究了磁性/非磁性超晶格中非线性体静磁波的色散性质.取如下位型:y轴垂直于超晶格中磁性层和非磁性层的界面,饱和磁化和外磁场沿z轴,波沿y轴或沿x轴传播.在微扰论的三阶近似下,获得了非线性波的色散方程,其中非线性项与波幅的模方成正比.数值结果显示:当波在y轴方向传播时,非线性的作用使波的频率向上漂移或向下漂移,这依靠磁性层的相对厚度和波矢的大小,但是对于在x轴方向传播的静磁波而言,非线性频移是向下的.对于一个适当的微波磁场强度,非线性效应非常明显.

Nonlinear bulk magnetostatic waves of magneticnonmagnetic superlattices are investigated with an effectivemedium method.We choose such geometry in which the y axis is normal to interfaces between magnetic and nonmagnetic layers.The saturation magnetization and applied magnetic field are directed along the z axis,and the waves propagate along the x or y direction.In the thirdorder appoximation,the dispersion equations,including a nonlinear term proportinal to ｜kψ/M0｜2 (k is the wave number,and ψ the wave amplitude),are presented .The numerical results show:(1)The nonlinear influence on the bulk modes is to produce an upward shift or down shift in frequency for the waves propagating along the y axis,depending the magnetic fraction and wave number.a downward shift in frequency is always seen for the waves moving parallel the x axis.(2) For a moderate strengh of microwave magnetic field,the nonlinear effects are very obvious.