Perpendicular magnetic anisotropy in ultrathin fcc iron films and surfaces at finite temperature

Abstract

The perpendicular magnetic anisotropy in one to six monolayer fcc iron films is studied by the Green-function method based upon the spin pinning model ( S⩾1) with out-of-plane spin orientation of the atoms at the surfaces, in which the strength of surface anisotropy D measures the fact that the spin be perpendicularly pinned to some degree at the surface, and taking into account the Heisenberg exchange interaction and magnetostatic dipole interaction. We calculate the surface anisotropy constant K s( T), the effective volume anisotropy constant K v( T) and the shape anisotropy constant K d( T) as functions of the thickness of ultrathin films and temperatures, and prove that there is a perpendicular remanence ( K v( T)- K d>0) for an intermediate range of thickness of ultrathin films and temperature, and that the transition temperature for the reversible transition between perpendicular and in-plane magnetization is sensitively affected by D. The calculated results for ultrathin fcc iron film with perpendicular surface anisotropy energy ≅o.5 meV/ atom agree with the experiments for the ultrathin films of fcc Fe on Cu(001).