A—B两层铁磁耦合薄膜中的自旋波共振谱

Spin-wave resonant spectra in an A-B ferromagnetic bilayer system

在Heisenberg模型的基础上,计入垂直于膜面的磁场,考虑表面各向异性场情况下,精确求解了简立方结构双层异质铁磁薄膜中的自旋波低能量子本征值问题.又在此基础上加上平行于膜面方向的交变磁场,应用量子理论严格推导了两层异质铁磁耦合薄膜中的自旋波共振激发,并在不同表面条件下计算了各种形式的自旋波共振谱.结果表明:1)共振峰强度与交变场振幅的平方成正比,与本征态中单个自旋反转对应的几率幅的模的平方成正比,即自旋波共振的平方律关系;2)由于表面各向异性场对不同形式的自旋波激发谱都产生影响,从而也影响自旋波的共振谱.

Based on the Heisenberg exchange model, a bilayer film composed of different ferromagnetic materials with simple cubic structure was investigated under the magnetic field perpendicular to the interface and anisotropic field at two surfaces. The spin-wave quantum eigenvalue was calculated at the low energy cases first, and then the spin-wave resonant excitation was deduced using quantum theory when adding the alternating magnetic field parallel to the interface. Finally, three types of the spin-wave resonant spectra were calculated with different surface conditions. The results show that： 1） the intensity of the resonance peak corresponding to a given nth spin-wave mode is directly proportional to the squared sum over its amplitudes across the bilayer film and the square of amplitude of the alternating field; 2） anisotropic field at two surfaces affects the different spectra variantly.