The magnetic relaxation processes following the dynamical excitation of the spin system of ferromagnets are investigated by ferromagnetic resonance (FMR) between 1 and $70\mathrm{GHz}$ using epitaxial ${\mathrm{Fe}}_3\mathrm{Si}$ films as a prototype system. Two relaxation channels, i.e., dissipative, isotropic Gilbert damping $G$ as well as anisotropic two-magnon scattering $\Gamma$, are simultaneously identified by frequency and angle dependent FMR and quantitatively analyzed. The scattering rates due to two-magnon scattering at crystallographic defects for spin waves propagating in ⟨100⟩ and ⟨110⟩ directions, $\gamma {\Gamma }_{⟨100⟩}=0.25\left(2\right)\mathrm{GHz}$ and $\gamma {\Gamma }_{⟨110⟩}=0.04\left(2\right)\mathrm{GHz}$, and the Gilbert damping term $G=0.051\left(1\right)\mathrm{GHz}$ are determined. We show that changing the film thickness from $8\text{to}40\mathrm{nm}$ and slightly modifying the Fe concentration influence the relaxation channels. Our results, which reveal the contributions of longitudinal and transverse relaxation processes may be of general importance for the understanding of spin-wave dynamics in magnetic structures.

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 $\Delta H_{\mathrm{pp}}.$ In this paper we focus specifically on $\Delta H_{\mathrm{pp}},$ looking at a variety of Fe, Co, Ni, and Gd films (thickness $<20\mathrm{}$ monolayers) epitaxially grown on different single-crystal substrates of various orientations, as well as an ${\mathrm{Fe}}_4/{\mathrm{V}}_4\mathrm{}\left(100\right)\mathrm{}$ 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 $\Delta H_{\mathrm{pp}}$ on film thickness and annealing conditions, as well as temperature, frequency, and magnetic-field orientation is examined. Particularly interesting is an angular dependence of $\Delta H_{\mathrm{pp}},$ 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.