Anomalous magnetic anisotropy of ultrathin Co films grown at 30 K on Au(111)

Atomically thick cobalt layers are grown on Au(111) by ultrahigh vacuum low-temperature deposition. Low-temperature deposition precludes the formation of three-dimensional cobalt bilayers clusters that grow in arrays at room temperature. As a result, ferromagnetic Co films with an anomalous in-plane magnetic anisotropy are obtained for thicknesses above 1.6 ML. Annealing produces an irreversible reorientation of the anisotropy from in plane to out of plane. However, a preferential in-plane anisotropy can be stabilized by covering the Co with a gold film.