Uniaxial magnetic anisotropy in Fe/GaAs(001): Role of magnetoelastic interactions

The origin of the in-plane uniaxial magnetic anisotropy of epitaxial Fe(001) films on GaAs(001) has been controversially attributed either to a magnetoelastic interaction or to oriented interface bonds. In order to check the relevance of magnetoelastic contributions we performed magneto-optic Kerr effect (MOKE) and magnetoelastic stress measurements on Fe(001) and Fe32Co68(001) bcc epitaxial films on GaAs(001) in a thickness range from several monolayers (ML) up to 100 ML. The magnetoelastic coupling coefficient B-2 of 30 ML films is +(8.4 +/- 1.4) MJ/m(3) for Fe(001) and -(23.2 +/- 3.7) MJ/m(3) for Fe32Co68(001), respectively. In spite of the opposite sign of B-2 for Fe and Fe32Co68, the same sign of the uniaxial anisotropy constant K-U(eff) is experimentally observed. It is concluded that the magnetoelastic interaction is not the dominating contribution to the uniaxial magnetic anisotropy in these systems.