PROPERTIES OF MBE-GROWN SUPERLATTICES AND ULTRA-THIN FILMS

Abstract

We have used Molecular Beam Epitaxy (MBE) to grow single-crystal Co/Pd superlattices and Co/TM (TM=Cu, Pd, Ag) bilayers and sandwiches along the three high-symmetry crystal directions; [001], [110], and [111]. In the case of Co/Pd superlattices, we previously reported from x-ray diffraction measurements that for small Co thicknesses the (001) oriented superlattices are coherently strained in-plane to near the bulk Pd lattice spacing. This strain leads to a very large in-plane magnetoelastic volume anisotropy for these superlattices. Here we report quantitative in situ RHEED measurements of Co deposited on Pd (001) that confirm this coherently strained growth. We have also used in situ polar Kerr ellipticity measurements to study the perpendicular magnetic behavior of Pd/Co/TM (111) sandwich structures, where TM is the non-magnetic transition metal overlayer Ag, Cu or Pd. We observed perpendicular loops with coercive fields of H c ≤ 200 Oe for the uncovered Co films for t co ≤ 6 Å, becoming in-plane above this thickness. However, subsequent deposition of just one atomic layer (≈ 2 Å) of any of the TM over the Co resulted in strongly perpendicular, square hysteresis curves with H c ≥ 900 Oe for all films in the Co thickness range studied.