Low-damping spin dynamics in thin sputtered FeGa films for strain-mediated spintronics

We report on the dynamic and quasistatic magnetic properties of ultrathin sputtered Ta/Fe81Ga19/glass thin films without buffer layers or post-deposition annealing. Ferromagnetic resonance measurements reveal a narrow peak-to-peak linewidth of 10.3±0.3 mT at 9.86 GHz, corresponding to an upper-bound Gilbert damping parameter of 2.5×10−2. These films also exhibit low coercivity in the range of 3–6 mT, confirming their soft magnetic character. Angular-dependent measurements indicate a predominantly twofold symmetry in the resonance field, while magnetization reversal displays a fourfold behavior. The origin of this discrepancy between dynamic and quasistatic anisotropies remains unclear and calls for further investigation. These results establish sputtered FeGa as a promising rare-earth-free magnetostrictive material combining strong magnetoelastic coupling with low-loss spin dynamics.