High-Speed Dynamics, Damping, and Relaxation Times in Submicrometer Spin-Valve Devices

Abstract

The dynamical response of spin-valve devices with line widths of 0.8 m has been measured after excitation with 160 ps magnetic impulses. The devices show resonant frequencies of 2 to 4 GHz which determine the upper limit of their operation frequency. The dynamical response can be fit with LandauLifshitz models to extract an effective uniform-mode damping constant, a um . The measured values of a um were between 0.04 and 0.01 depending on the magnitude of the longitudinal bias field. The appropriate damping coefficient for use in micromagnetic modeling, amm , was extracted from the dynamical response with large longitudinal bias field. This value was used to model the switching of a 0.1 m x 1.0 m magnetoresistive random access memory (MRAM) cell. The micromagnetic model included shape disorder that is expected to be found in real devices. The simulations showed that, while the magnetization reverses rapidly (< 0.5 ns), it took several nanoseconds for the energy to be removed from the ma..