Large perpendicular magnetic anisotropy in magnetostrictive Fe1−xGax thin films
Résumé
In this work we report the appearance of a large perpendicular magnetic anisotropy (PMA) in Fe1−xGax thin films grown onto ZnSe/GaAs(001). This arising anisotropy is related to the tetragonal metastable phase in as-grown samples recently reported [M. Eddrief et al., Phys. Rev. B 84, 161410 (2011)]. By means of ferromagnetic resonance studies we measured PMA values up to ∼5×105 J/m3. PMA vanishes when the cubic structure is recovered upon annealing at 300∘C. Despite the important values of the magnetoelastic constants measured via the cantilever method, the consequent magnetoelastic contribution to PMA is not enough to explain the observed anisotropy values in the distorted state. Ab initio calculations show that the chemical ordering plays a crucial role in the appearance of PMA. Through a phenomenological model we propose that an excess of next-nearest-neighbor Ga pairs (B2-like ordering) along the perpendicular direction arises as a possible source of PMA in Fe1−xGax thin films.