New characteristic parameter of energy loss in permalloy

Abstract

Characteristic parameters of energy storage and loss in soft magnetic materials, product S of initial susceptibility χ_i and resonance frequency ω_r and product L of maximum χ_m^'' and half width ∆ω of imaginary part, were introduced in Permalloy films. Expressions of characteristic parameters were derived from Landau-Lifshits-Gilbert equation with a general anisotropic free energy model. It was found S= L equals to intrinsic quantity of soft magnetic materials Q=γM_s √(((H_∥+H_⊥ ))⁄H_∥ ), where γ is the gyromagnetic ratio, M_s is the saturation magnetization, and H_⊥ and H_∥ are mutually orthogonal effective magnetic fields. In the presence of eddy curent, it was found S remains equal to Q while L<Q results from inhomogeneity of microwave magnetic field caused by eddy current. Moreover, a linear scale of L/S versus Gilbert damping factor α was found in Permalloy films with different thicknesses. Hence, our findings provide a new perspective on energy storage and loss of soft magnetic materials.