Preparation and magnetic properties of the CoO/Co bilayer

The results of the preparation, characterization and magnetic properties of a CoO/Co interface are discussed. This interface was realized by ultraviolet irradiation of a 4 nm Co layer deposited with a gold buffer layer on a GaAs(111) substrate. The Co oxide analyzed by XPS and AFM 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 effect in polar configuration from modelization of the M(H) curve. This discrepancy is discussed in terms of the difference of sensing the interfacial coupling in the two cases due to atomic steps. (C) 1998 Elsevier Science B.V. All rights reserved.