INFLUENCE OF SUBSTRATE SURFACE RECONSTRUCTION ON THE GROWTH AND MAGNETIC-PROPERTIES OF FE ON GAAS(001)

We have studied the magnetic and structural properties of epitaxial bc c Fe(001) films grown at 175 degrees C on molecular-beam epitaxy-prepa red GaAs(001)-2X4 and -c(4X4) reconstructed surfaces, with film thickn esses ranging up to similar to 30 ML (similar to 43 Angstrom). We pres ent measurements of the thickness-dependent evolution of the magnetic properties of the Fe films as determined by in situ magneto-optic Kerr effect. We find that the magnetic properties and growth mode are simi lar for both 2X4 and c(4x4) reconstructions, although the initial adso rption sites and island nucleation as measured by scanning tunnelling microscopy are clearly dominated by the substrate surface reconstructi on. The onset of room-temperature ferromagnetism occurs at 6 ML for gr owth on both GaAs surface reconstructions. At this coverage, the measu red Curie temperature (similar to 100 degrees C) is significantly redu ced from that of bulk alpha-Fe (770 degrees C). The anisotropy is domi nated by a uniaxial component such that the two [110] axes are inequiv alent for all coverages studied. Shape anisotropy does not appear to p lay a significant role.