Research on low spin-damping magnetic materials for the power-efficient spin-controlled devices

自旋阻尼是影响硬盘驱动器速度和正在开发的自旋存储器件功耗的一个重要现象。了解其物理来源是这些设备材料设计的必要条件。我们研究了含Co或Ni的Fe薄膜的自旋（吉尔伯特）阻尼系数。Co或Ni是三维过渡金属，是广泛使用的磁性材料。在高真空条件下制备薄膜，然后对部分薄膜进行退火以提高结晶度。用铁磁共振谱法测量了Gilbert阻尼系数。退火后，阻尼系数略有降低。从理论上预测了自旋阻尼取决于电子在金属中的散射速率。我们的研究结果表明，随着结晶度的提高，薄膜的阻尼降低是因为散射率降低。

Spin damping is an important phenomenon which affects the speed of hard disk drives and the power consumption of spin-memory devices under development. Understanding its physical origin is mandatory for the material design of these devices. We have investigated the spin (Gilbert) damping coefficients of Fe thin films with dilute concentrations of Co or Ni, which are 3d transition metals and are widely-used magnetic materials. The films were fabricated in high-vacuum and later some of them were annealed to improve the crystallinity. The Gilbert damping coefficients were measured by the ferromagnetic resonance spectroscopy. It is found that the damping coefficients reduce slightly after annealing. It is theoretically anticipated that the spin damping depends on the scattering rate of electrons in metals. Our findings infer that damping of the films reduces because the scattering rate lowers as the crystallinity improves.