Magnetostatic wave propagation losses in an anisotropic insulator

Abstract

Propagation losses are calculated for magnetostatic surface waves in slabs of YIG and LiFe₅O₈. A phenomenological (Gilbert) magnetic damping is assumed and known magnetic parameters are used. The propagation loss factor L (dB/μsec) is calculated as a function of frequency. At high frequencies we find that L is proportional to frequency with a slope of 4π(76.4λ/γ²M), where λ is the damping parameter, γ is the gyromagnetic ratio, and M is the magnetization. At low frequencies, L approaches a limiting value of 4π(76.4λ/γ). The quantity L is independent of slab thickness, although both loss and delay time are functions of thickness for a given slab length. Our calculated L is in reasonable agreement with recent measurements. As expected, magnetic anisotropy has a greater effect on L for LiFe₅O₈ than for YIG.