Magnetic anistropy in ultrathin epitaxial Fe/Ag(100) films with overlayers

In situ Brillouin light-scattering and magneto-optical Kerr effect measurements have been used to determine the values of the magnetic anisotropy constants in ultrathin epitaxial Fe/Ag(100) films both during the deposition of the Fe layer and also during the deposition of overlayers of Ag and Cr. The structural properties of the films have been investigated by means of reflection high-energy electron diffraction and low-energy electron diffraction. We show that the values of the cubic magnetocrystalline anisotropy constant K-l and the magnetic surface anisotropy constant K-s are strongly dependent upon the value of the Fe layer thickness d, and that they differ in sensitivity to the surface structure of the substrate. We find that the thickness of a Ag or Cr overlayer must be at least 3 ML thick before the value of K-s is saturated. Cr and Ag capping layers are found to have a qualitatively different effect upon the magnetic anisotropy which we attribute to the presence of magnetic order in the Cr.