Brillouin Light Scattering Study of the Magnetic Anisotropy in bcc-Fe(100) Ultrathin Films Grown on GaAs(100) Surfaces With Different Reconstructions

We investigated the magnetic anisotropy of ultrathin bcc-Fe (001) films with a fcc-Au(001) cover layer, grown onto GaAs (001) (4 times 1) and (2 times 6)/(3 times 6) reconstructed surfaces. The magneto-optical Kerr effect hysteresis loops revealed existence of a strong in-plane uniaxial magnetic anisotropy in the Fe films grown on both the surfaces. Details of the in-plane uniaxial anisotropy (K_U), cubic anisotropy (K_C), and effective demagnetization field (4piM_eff) were studied by Brillouin light scattering method. We observed a stronger reduction of K_U, K_C, and 4piM_eff in thinner Fe layers (below 1.3 nm) grown on both the surfaces. In the case of Fe films grown on GaAs (4 times 1) surface, anisotropies observed were smaller than that for the (2 times 6)/(3 times 6) surface. This reflects the role of surface structure in determining the magnetic anisotropies.