MAGNETIC-ANISOTROPY OF METAL CO METAL AND METAL CO INSULATOR SANDWICHES

In situ polar Kerr-effect measurements have been used to study the magnetic anisotropy of MBE-grown Au(111)/Co/X and Pd(111)/Co/X sandwiches, where X is the nonmagnetic metal Ag, Au, Cu, and Pd or the insulator MgO. For the metals it was recently found that the magnitude of the Co/X perpendicular interface anisotropy is strongly peaked at ∼1 atomic layer (1.5-2.5 Å) coverage. To investigate structural influences on the anisotropy, reflection high-energy electron diffraction (RHEED) and low-energy electron diffraction (LEED) have been used to measure changes resulting from overlayer coverage. Analysis of digitized RHEED images captured every ∼1 Å during metal overlayer coverage shows no abrupt change of the in-plane lattice constant. The out-of-plane lattice spacing has also been investigated as a function of nonmagnetic metal coverage by measuring LEED I-V curves along the (0,0) rod. In the case of Cu, where the LEED behavior is nearly kinematic, no evidence was seen of any abrupt structural changes at ∼1 atomic layer coverage. These results suggest the observed peak in magnetic anisotropy is not structural in origin. To further study this phenomenon, the influence of an insulating overlayer, MgO, on the perpendicular magnetic properties has been measured.