Influence of Growth Temperature on the Magnetic Anisotropy of Co Grown on GaAs (001) Substrates

The morphology and the in-plane magnetic anisotropy changes in polycrystalline hexagonal-closed-packed (hcp) Co grown on a GaAs (001) substrate have been extensively investigated as a function of the growth temperature. Alternating-gradient magnetometry (AGM) measurements revealed a manifest change in the magnetic anisotropy from uniaxial to cubic as the growth temperature was increased from room temperature to 200 degrees C. The Co grown at room temperature shows that Co islands elongated along the [110] direction corresponding to the easy axis of the uniaxial magnetic anisotropy. The Co grown at 200 degrees C showed an isotropic morphology with cubic-magnetic anisotropy. The phase transition from a body-centered-cubic to a hexagonal-closed-packed phase was retarded at the higher growth temperatures. The experimental results indicate that the growth temperature is the key factor determining the morphology, as well as the magnetic anisotropy, of Co grown on GaAs (001) substrates.