Magnetic phase diagram study of ultrathin Co/Si(111) films

The magnetic properties of ultrathin Co/Si(111) films were studied by the s urface magneto-optic Kerr effect technique. A magnetic phase diagram has be en successfully established between 120 and 500 K. Several phases were obse rved, i.e. a nonferromagnetic Co-Si compound, a low Curie temperature Co fi lm, canted out-of-plane anisotropy, and in-plane anisotropy. The nonferroma gnetic Co-Si compound can be reduced by decreasing the substrate temperatur e. With an Ag buffer layer, the thermal stability of the magnetization for a Co/Si(111) film is lowered. From Auger electron spectroscopy measurement, Ag atoms in the Co/Ag/Si(111l) film segregate to top layers even below 350 K. The segregation of Ag atoms to the top layer may damage the magnetic do mains in the Co layer and causes the lower thermal stability of the magneti zation in the Co/Ag/Si(111) film. (C) 2000 Elsevier Science B.V. All rights reserved.