垂直场下磁性薄膜中的铁磁共振现象

Ferromagnetic resonance phenomenon of magnetic thin film under a perpendicular field

将铁磁共振频率看成外磁场的函数,讨论了垂直场下磁性膜中的铁磁共振现象.结果显示:当外磁场平行于膜面,并考虑磁膜具有垂直磁晶各向异性情形时,其磁共振频率随外磁场的变化分为高频支和低频支两种情况,具体的依赖关系取决于磁膜内磁晶的各向异性;当外磁场垂直于膜面,其磁共振频率随外磁场的关系仅存在一支,一般地,磁共振频率随外磁场的增加单调地非线性减小,但当立方磁晶各向异性场H_(k1)与单轴磁晶各向异性场H_a之比值介于2/3<|H_(k1)/H_a|<1时,其磁共振频率随外磁场的增加单调增加,这与相关的实验结果一致.研究结果表明:磁薄膜中有无垂直于膜面的磁各向异性可以通过其磁共振谱的测量进行辨析.

Regarding ferromagnetic resonance frequency as a function of the perpendicular external magnetic field, the ferromagnetic res- onance phenomenon is investigated. The results show that for the case where the external magnetic field is parallel to the its plane and the magnetic thin film has a perpendicular uniaxial magnetiocrystalline anisotropy, magnetic resonance frequency is divided into two categories, i.e., low frequency branch and high frequency branch, their specific relation depends on the magnetic anisotropy of the magnetic film; when external magnetic field is perpendicular to the systemic plane, the magnetic resonance frequency displays only a branch with the change of external magnetic field. In general, the magnetic resonance frequency decreases with the increase of the external magnetic field nonlinearly and monotonically. However, when the ratio between the cubic magnetocrystalline anisotropic field Hkl and uniaxial magnetocrystalline anisotropic field Ha is about 2/3 〈 ｜Hkl/Ha｜ 〈 1, the magnetic resonance frequency increases with the increase of external magnetic field, which is in good agreement with the experimental results. The results show that through magnetic resonance spectrum, the vertical magnetic anisotropy in magnetic thin film can be distinguished.