Magnetic properties of ultrathin Co films on Si (111)

Ultrathin cobalt films on clean (7×7) and Au covered Si (111) substrates were prepared by molecular beam epitaxy. The structure was studied by using scanning tunnelling microscopy and low energy electron diffraction. Magnetic properties were determined with the magneto-optic Kerr effect. It was found that Co nucleates in grains that prefer to grow along the bunched step edges of the Si substrate ([112̄] direction), which induces a strong in-plane uniaxial anisotropy. By introducing Au buffer layers, the magnetic characteristics were improved by preventing the silicide reaction between Si and Co. Moreover, the tendency for step decoration disappears gradually results in the in-plane uniaxial anisotropy reduction.