CoFeB-LiNbO颗粒膜$_3$中FMR线在金属-绝缘体转变附近的增宽机制
Mechanisms of FMR line broadening in CoFeB-LiNbO$_3$ granular films in the vicinity of metal-insulator transition
摘要：
利用铁磁共振（FMR）技术研究了不同铁磁相（FM）含量的金属-绝缘体（CoFeB）$_x$（LiNbO $_3$）$_{100-x}$纳米复合薄膜$x$.在薄膜的金属-绝缘体转变（MIT）附近观察到FMR线形状的强烈变化，其中跳跃型电导率$σ$修改为强晶间隧穿的制度，其特征在于在高温下的对数依赖性$σ(T)$。结果表明，在低于MIT时，FMR线宽主要取决于薄膜平面内局部各向异性轴的不均匀分布。在MIT以上，这种不均匀性对谱线展宽的贡献减小。同时，双磁振子磁弛豫过程开始在线宽的形成中起重要作用。所观察到的行为表明的关键作用，粒子间交换的隧道制度MIT以上的纳米复合材料。
英文摘要：
Metal-insulator (CoFeB)$_x$(LiNbO$_3$)$_{100-x}$ nanocomposite films with different content of the ferromagnetic (FM) phase $x$ are investigated by ferromagnetic resonance (FMR) technique. A strong change of the FMR line shape is observed in the vicinity of metal-insulator transition (MIT) of the film, where the hopping-type conductivity $σ$ modifies to the regime of a strong intergranular tunnelling, characterized by a logarithmic dependence $σ(T)$ at high temperatures. It is shown that below MIT, the FMR linewidth is mainly determined by the inhomogeneous distribution of the local anisotropy axes in the film plane. Above MIT, the contribution of this inhomogeneity to the line broadening decreases. At the same time, two-magnon magnetic relaxation processes begin to play a significant role in the formation of the linewidth. The observed behaviour indicates the critical role of interparticle exchange in the tunnelling regime above MIT of the nanocomposite.
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