Nonuniform apparent relaxation from dephasing of magnetostatic wave modes in a confined microdisk

Abstract

We report the nonuniform apparent relaxation due to the spatially inhomogeneous dephasing of magnetostatic wave modes in a confined Permalloy microdisk investigated by picosecond time-resolved scanning Kerr microscopy. Spin precession in the disk shows a considerable nonuniformity in the relaxation time along the direction of a bias magnetic field. The nonuniform apparent relaxation is well reproduced by micromagnetic simulation using uniform values of damping constant. This implies that the spinwaves in the microdisk plays a significant role in the relaxation process. The simulation study, based on the analysis of spinwave modes, reveals that the spatial relaxation variation is mainly caused by the spatially inhomogeneous dephasing between the fundamental mode and magnetostatic backward volume wave mode.