EFFECT OF SUBMONOLAYER COVERAGE ON MAGNETIC-ANISOTROPY OF ULTRATHIN COBALT FILMS M/CO/AU(111) WITH M=AU, CU, PD

Using in situ polar magneto-optical Kerr-effect measurements, the variation of the Kerr rotation and magnetic anisotropy of a (0001)Co ultrathin film on a (111)Au substrate has been precisely recorded, during the first stages of the growth of an overlayer of metal M=Au, Cu, and Pd. As reported earlier, a drastic increase of the magnetic anisotropy was observed, with a peak around 1 monolayer of overlayer thickness. From a careful study of the variation of the remanent Kerr rotation, it could be shown that only the interface contribution to the anisotropy changes with the overlayer thickness, while the bulk contribution remains mostly constant. The overall behavior can be interpreted in terms of electronic effects in the metal overlayer, acting on the interface anisotropy via band hybridization at the interface.