Magnetic anisotropy in Fe₈₁Ga₁₉/MgO (1 0 0) films sputtered at different powers

We present a study of the magnetic anisotropy of Fe₈₁Ga₁₉ thin alloy films (90 nm thick), sputter deposited on MgO (1 0 0) wafers for sputtering powers in the range 35 W≤P≤75 W. The films have been characterized at room temperature using angular magnetization remanence and ferromagnetic resonance measurements at 9.7 GHz.We have found that for low sputtering powers the films grow epitaxially presenting an in-plane cubic magnetic anisotropy of magnetocrystalline origin, which changes to uniaxial when P is increased. The analysis of the resonance linewidth indicates that the films tend to be more disordered as the sputtering power increases. However, the film sputtered at 75 W, in which the induced uniaxial anisotropy dominates, has the smallest linewidth. The transition from cubic to uniaxial magnetic anisotropy may be understood if we assume that the quality of the epitaxial growth deteriorates when the films are sputtered at high deposition rates.