PREPARATION AND MAGNETIC-PROPERTIES OF THE COO CO BILAYER/

The results of the preparation, characterization and magnetic properti es of a CoO/Co interface are discussed. This interface was realized by ultraviolet irradiation of a 4 nm Co layer deposited with a gold buff er layer on a GaAs(111) substrate. The Co oxide analyzed by XPS and AF M revealed a continuous 1.7 nm thick layer with a rms roughness of 0.6 nm and mostly CoO at the interface. Longitudinal magneto-optical Kerr loops evidence a strong initial in-plane anisotropy which disappears on oxidation. Values of the unidirectional exchange coupling at the Co /CoO interface were obtained: 0.1 erg/cm(2) from SQUID measurement at 5 K after field cooling and 0.6 erg/cm(2) with magneto-optical Kerr ef fect in polar configuration from modelization of the M(H) curve. This discrepancy is discussed in terms of the difference of sensing the int erfacial coupling in the two cases due to atomic steps. (C) 1998 Elsev ier Science B.V. All rights reserved.