Effect of Surface Roughness on Ferrimagnetic Resonance Linewidth Measurements

Abstract

From room‐temperature ferrimagnetic resonance linewidth measurements on both single‐crystal and polycrystalline ferrite and garnet specimens, it is concluded that the surface contribution to the linewidth may be represented by ΔH_surface=ξ4πM_s/d, where 4πM_s is the saturation magnetization, d the sphere diameter, and ξ is a parameter dependent on the surface condition. Experimental results are presented in a manner which clearly indicates the direct dependence on 4πM_s and the inverse dependence on sphere diameter which represents the ratio of the surface region volume to total volume. The parameter ξ is shown to vary with surface finish for coarse and medium textured surfaces. By comparing the linewidths of polished spheres with the extrapolated results for spheres of infinite diameter obtained from plots of ΔH vs 1/d, it is verified that the surface effects may be removed by polishing. Finally, it is emphasized that linewidths of polycrystalline materials may be very inaccurate if the surface is not polished, particularly where the material has a large magnetization and the spherical sample is small.