ANOMALOUS INTERFACE MAGNETISM IN ULTRATHIN CO FILMS WITH INPLANE ANISOTROPY

Using the magneto-optical Kerr effect, we have observed a striking sensitivity of the magnetic properties of ultrathin Co/Cu(001) films to submonolayer coverages of Cu. In particular large nonmonotonic changes of the coercive field Hc, the height of the M-H loop (magneto-optical signal), and the ratio S of remanent and saturation magnetizations are observed. With increasing Cu thickness the coercivity first sharply decreases, reaching a minimum at around 0.2 monolayer (ML) followed by a gradual increase. In contrast, the magneto-optical signal is found to peak strongly at the same Cu overlayer thickness of 0.2 ML, decaying in magnitude with further Cu coverage.