Magnetic and structural properties of (Ga,Mn)As/(Al,Ga,Mn)As bilayer films

We investigate the dependence of the magnetic and structural properties of (Ga,Mn)As/(Al,Ga,Mn)As bilayer films on the stoichiometry of the interface region. For films incorporating a thin As-deficient layer at the interface, the out-diffusion of interstitial Mn from the bottom layer is strongly suppressed, resulting in a large difference in T C and magnetic anisotropy between the two layers. X-ray reflectivity measurements show that the suppression of interstitial diffusion is correlated with an increased interface roughness. When the As-deficient interface layer is thicker than 2.5 nm, the in-plane uniaxial magnetic easy axis rotates from the [1-10] to the [110] crystalline axis.