Magnetic anisotropy of Cs adsorbed fcc Co(0 0 1) thin films on Cu(0 0 1) surfaces

Structure and magnetic properties are studied for Cs adsorbed Co(0 0 1) thin films epitaxially grown on clean Cu(0 0 1) surfaces with steps along [1 0 0] direction. A quasi-hexagonal order was found in the structure of single atomic-layer Cs on the surface at 120 and 300 K as observed for Cs on clean Cu(0 0 1) surfaces. The magnetic hysteresis loops were measured at 120 and 300 K using magneto optical Kerr effect. The magnetic anisotropy induced by the steps along [1 0 0] direction changes at 120 K when the density of Cs at the surface exceeds the half of the single atomic-layer. Simultaneously, the coercive field along [1 0 0] direction increases. The charge transfer from Cs to the substrate is discussed as a possible origin of these changes.