Giant enhancement of magneto-optical response and increase in perpendicular magnetic anisotropy of ultrathin Co/Pt(111) films upon thermal annealing

The annealing effects on the magnetic properties, crystallographic structur e, and alloy formation, were studied for Co/Pt (111) ultrathin films at cov erages up to 6.6 ML, using in situ magneto-optical Kerr effect, low energy electron diffraction, Auger electron spectroscopy,and ultra-Violet photoele ctron spectroscopy. After the postdeposition annealing in the temperature r ange. of 500-800 K, a significant increase in perpendicular magnetic anisot ropy at high coverages and a large enhancement of magneto-optical response with the value about 200%-300% of that before annealing for all coverages i nvestigated are observed. Both findings are shown to be correlated to the f ormation of a kind of Co-Pt interface (surface) alloy. This is expected to be mainly attributed to the transfer of strong spin-orbit coupling of the P t into the Co magnetic orbital due to the hybridization during interface al loy formation. (C) 1999 American Vacuum Society. [S0734-2101(99)06805-0].