National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P. R. China.
Department of Mathematics and Physics, Nanjing Institute of Technology, Nanjing 211167, P. R. China.
Sci Rep. 2017 Mar 6;7:43971. doi: 10.1038/srep43971.
A 3.5 nm amorphous CoFeB film was sputtered on GaAs (001) wafer substrate without applying magnetic field during deposition, and a significant in-plane uniaxial magnetic anisotropy (UMA) field (H) of about 300 Oe could be achieved. To precisely determine the intrinsic Gilbert damping constant (α) of this film, both ferromagnetic resonance (FMR) and time-resolved magneto-optical Kerr effect (TRMOKE) techniques were utilized. With good fitting of the dynamic spectra of FMR and TRMOKE, α is calculated to be 0.010 and 0.013, respectively. Obviously, the latter is 30% larger than the former, which is due to the transient heating effect during the TRMOKE measurement. In comparison with ordinary amorphous CoFeB films with negligible magnetic anisotropies, α is enhanced significantly in the CoFeB/GaAs(001) film, which may be mainly resulted from the enhanced spin-orbit coupling induced by the CoFeB/GaAs interface. However, the significant in-plane UMA plays minor role in the enhancement of α.
在沉积过程中没有施加磁场的情况下，在 GaAs（001）晶片衬底上溅射了一层 3.5nm 的非晶 CoFeB 薄膜，可实现约 300Oe 的显著面内单轴各向异性（UMA）场（H）。为了精确确定该薄膜的固有 Gilbert 阻尼常数（α），同时使用了铁磁共振（FMR）和时间分辨磁光克尔效应（TRMOKE）技术。通过对 FMR 和 TRMOKE 的动态光谱进行良好拟合，分别计算出α为 0.010 和 0.013。显然，后者比前者大 30％，这是由于在 TRMOKE 测量过程中存在瞬态加热效应。与具有可忽略磁各向异性的普通非晶 CoFeB 薄膜相比，CoFeB/GaAs（001）薄膜中的α显着增强，这可能主要是由于 CoFeB/GaAs 界面引起的增强的自旋轨道耦合所致。但是，显著的面内 UMA 在增强α方面的作用较小。
