SURFACE NANOPATTERNING EFFECTS, STRUCTURE AND MAGNETIC PROPERTIES OF EPITAXIAL Ni FILMS

Abstract

We have studied the correlation between film structures and the azimuthal dependence of the magnetization reversal in (001) and (111) Ni films grown on MgO substrates using molecular beam epitaxy (MBE). For as-grown (001) Ni films, the coercive field exhibits four-fold azimuthal symmetry while in-situ annealed films exhibit additional uniaxial anisotropy. In-situ STM images show surface stripe nanopatterning on the annealed films, which is absent in the as-grown ones. Cross sectional TEM seems to indicate the presence of a highly ordered interfacial layer that we postulate may be fcc NiO . Tetragonal distortion of this layer upon annealing may have induced the uniaxial anisotropy observed in the magnetic properties. Polarized neutron reflectivity measurements performed on some of the films are correlated with the interfacial surface structure and the magnetic anisotropy.