Intrinsic Gilbert damping constant in Co/sub 2/MnAl Heusler alloy films

Abstract

Intrinsic /spl alpha/-damping constants of Co/sub 2/MnAl Heusler alloy films prepared by magnetron sputtering were investigated. After deposition of Co/sub 2/MnAl films, the films were annealed at 200-400/spl deg/C to control the crystal structure and the atomic order between Co, Mn, and Al sites. Ferromagnetic resonance (FMR) technique was used to obtain /spl alpha/ values of Co/sub 2/MnAl films in this study. Out-of-plane angular dependences of the resonance field (H/sub R/) and linewidth (/spl Delta/H/sub pp/) of FMR spectra were measured and fitted using the Landau-Lifshitz-Gilbert (LLG) equation. The authors were able to fit all experimental results well because of the lack of inhomogeneities in prepared Co/sub 2/MnAl films. The /spl alpha/-damping constants obtained from the fitting results decreased with increasing annealing temperature and showed a minimum value of 0.007 at 300/spl deg/C. It was found that a degree of B2 structure order can sensitively affect /spl alpha/-damping constants of Co/sub 2/MnAl films.