Correlations between ferromagnetic-resonance linewidths and sample quality in the study of metallic ultrathin films

Abstract

Ferromagnetic resonance is commonly used in the study of thin ferromagnetic films. In past investigations, most attention has been concentrated on the resonance field ${H}_{r},$ with relatively little consideration for the information contained in the peak-to-peak linewidth $\ensuremath{\Delta}{H}_{\mathrm{pp}}.$ In this paper we focus specifically on $\ensuremath{\Delta}{H}_{\mathrm{pp}},$ looking at a variety of Fe, Co, Ni, and Gd films (thickness $<20$ monolayers) epitaxially grown on different single-crystal substrates of various orientations, as well as an ${\mathrm{Fe}}_{4}/{\mathrm{V}}_{4}(100)$ multilayer. We identify common features in the linewidths which correlate with other film properties, such as intrinsic spin-damping mechanisms, and the structural and magnetic quality. The dependence of $\ensuremath{\Delta}{H}_{\mathrm{pp}}$ on film thickness and annealing conditions, as well as temperature, frequency, and magnetic-field orientation is examined. Particularly interesting is an angular dependence of $\ensuremath{\Delta}{H}_{\mathrm{pp}},$ seen most clearly in ${\mathrm{Fe}}_{4}/{\mathrm{V}}_{4}$ which is related to the crystallographic axes and appears to be correlated with the intrinsic damping of the spins.