We determined the Gilbert damping constants of Fe-Co-Ni and Co-Fe-B alloys with various compositions and half-metallic Co 2 MnAl Heusler alloy films prepared by magnetron sputtering. The ferromagnetic resonance (FMR) technique was used to determine the damping constants of the prepared films. The out-of-plane angular dependences of the resonance field (H R ) and line width (ÁH pp ) of FMR spectra were measured and fitted using the Landau-Lifshitz-Gilbert (LLG) equation. The experimental results fitted well, considering the inhomogeneities of the films in the fitting. The damping constants of the metallic films were much larger than those of bulk ferrimagnetic insulators and were roughly proportional to ðg À 2Þ 2 , where g is the Lande g factor. We discuss the origin of magnetic damping, considering spin-orbit and s-d interactions.

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We investigated the Gilbert damping constant of the Heusler Co 2 MnSi(001) films epitaxially grown on a MgO(100) substrate by a ferromagnetic resonance technique. The angular variation in resonance field in the in-plane geometry exhibited a maximum when the field was applied parallel to the [110] direction (easy axis), and its relative minimum corresponded to the H k ½100 hard axis. Experimental results were fitted with theoretical results; the g-value, effective magnetization and anisotropy constants were determined. The magneto-crystalline anisotropy of the films decreased after the films were postannealed at 400 C. The Gilbert damping parameter was anisotropic and had a minimum value at 300 C.

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where γ is the gyromagnetic ratio, µ B is the Bohr magneton, D(E F ) is the total density of states (DOS) at the Fermi energy E F , g is the Lande g factor, and τ is the electron momentum scattering time. Equation (1) indicates that α varies with D(E F ), so that α generally tends to be smaller for magnetic alloys with lower D(E F ), such as half-metals, as noted by one of the present authors [5]. The typical value of α for Fe is 2 × 10 −3 [6-8], while even smaller values were reported in half-or full-Heusler alloys with a half-metal gap in the minority spin state, e.g. 1.0-1.5 × 10 −3 for Co 2 FeAl films [5, 9-11] and 1.0 × 10 −3 for NiMnSb [12,13]. The current research interest

Co 2 Fe Si films were prepared using magnetron sputtering technique on Cr buffer layers and MgO(001) substrates at various annealing temperatures. We investigated the crystal structures, magnetic properties (Ms and Hc), surface roughness, and magnetic damping constants (α) of the prepared Co2FeSi films. Out-of-plane angular dependences of the resonance field and the linewidth of the ferromagnetic resonance spectra were measured and fitted using the Landau-Lifshitz-Gilbert equation to determine the damping constant. The as-deposited Co2FeSi film exhibited an amorphous and disordered structure; the α value was 0.008. In contrast, the Co2FeSi films annealed over 300°C showed epitaxial growth and had a (001)-oriented and L21 ordered structure. Both disordered and L21 ordered Co2FeSi films showed similar α values.