Magnetic properties of epitaxial Fe(Si1-xFex) films grown on Si(111)

Iron silicide thin films (200 Angstrom Fe(Si1-xFex) with 0 less than or equal to x less than or equal to 1 and local cubic CsCl structure) have been grown by coevaporation at room temperature (RT) on Si(1 1 1). X-ray magnetic circular dichroism (XMCD) and magneto-optic Kerr effect (MOKE) measurements indicate that the films are ferromagnetic at RT for x ranging from 1 (pure Fe) to 0.15 (Fe1.35Si). The magnetization is parallel to the him surface, and the magnetic anisotropy is uniaxial, with the easy axis lying along a [(1) over bar 0 1](Si) crystallographic direction and the hard axis along a [1 (2) over bar 1](Si) direction of the substrate. MOKE measurements show that the magnitude of the saturation field increases with increasing Si concentration, while XMCD data indicate that the average local magnetic moment carried by the Fe atoms decreases with decreasing Fe concentration. Models which involve the diminution of the number of Fe nearest neighbors are proposed for the description of the behavior of the Fe moments. (C) 1999 Elsevier Science B.V. All rights reserved.