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

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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.