Dynamic Properties of Permalloy Thin Films

Abstract

Free oscillations, switching and ferromagnetic resonance of Permalloy thin films are measured changing, for each film, various parameters including temperature. It is shown that the damping factor λ in the free oscillations of Permalloy thin film is composed of three parts as
λ=λ_in+λ_edd+kH_y,
where λ_in is due to the intrinsic damping plus the damping from the anisotropy dispersion, λ_edd due to the eddy current damping, which is represeted as 1.0×10¹⁷d² (cps) as a function of the thickness d, and kH_y due to the high power effect probably caused by the increased excitation of the spin wave modes. In the last term H_y is the amplitude of the applied pulse field and k is a constant which depends on the film thickness. The value of λ_in is about 1.05×10⁸ (cps) and is in good agreement with the minimum value of λ ever obtained for Permalloy films by various measurements.