Anomalous magnetic anisotropy in ultrathin transition metals

Abstract

We have used in situ polar Kerr effect measurements to probe directly the magnetic anisotropy of ultrathin MBE-grown Co films with and without overlayers of various nonmagnetic metals (X=Ag, Cu, Pd). To investigate the Co/X interface, we measured perpendicular hysteresis curves as a function of overlayer coverage. We find the magnitude of the perpendicular anisotropy is strongly peaked near ∼1 atomic layer (1.5–2 Å) coverage for Ag and Cu overlayers. For Cu, the overlayer with the strongest effect, the total anisotropy energy rapidly decreases by a factor of 3 from its peak value after a total coverage of only ∼2 atomic layers (4 Å) of Cu.