VARIABLE-TEMPERATURE STM AND KERR STUDIES OF ULTRATHIN FILMS OF CO ONAU(111) - FROM SELF-ORGANIZED CLUSTERS TO CONTINUOUS FILMS

UHV-grown ultrathin Co films on Au(111) were studied in situ by variab le temperature scanning tunneling microscopy and polar magneto-optical Kerr effect. The relationship between the morphology of the deposits, their dimensionality, and their magnetic behavior was studied as a fu nction of coverage. At low coverage, self-organized 2-D arrays of bila yer islands nucleate at the herringbone reconstruction of Au(111), whe reas at a coverage of 1.6 ML the surface is already covered by partly coalesced bilayer islands. At 3.2 ML, additional Co layers have formed on top of existing islands, and growth develops into the third dimens ion. Ferromagnetism is observed for both coverages at room temperature . As the Co coverage is further increased, the island size distributio n broadens and the surface becomes rougher The magnetization is perpen dicular to the film plane from 1.6 to 6.4 ML. At about this coverage, the magnetization starts rotating from out of plane to in-plane.