TEMPERATURE-DEPENDENT MAGNETIC SURFACE ANISOTROPY IN ULTRATHIN FE FILMS

The temperature dependence of the uniaxial surface anisotropy, K-u(T), in ultrathin Fe films (4-10 atomic layers) grown on Cu(100) is determ ined by comparing the dipole and anisotropy energies at the spin reori entation temperature for films of varying thickness. It is observed th at the uniaxial anisotropy has a weak temperature dependence compared to the bulk constants for Fe. The measured exponent of Gamma(u) = 2.6( 0.5) agrees well with the l(l + 1)/2 law, which is obtained from a spi n fluctuation model where l = 2 at the surface. This shows that the sp in reorientation transition can be understood as being driven by therm al spin fluctuations. (C) 1996 American Vacuum Society.