GENERIC SOURCE OF PERPENDICULAR ANISOTROPY IN AMORPHOUS RARE-EARTH TRANSITION-METAL FILMS

We show that the magnetic dipolar energy of antiparallel dipoles in the surface layers contributes to the intrinsic uniaxial perpendicular anisotropy in amorphous rare-earth-transition-metal films. The volume anisotropy energy density K(u) of this contribution depends inversely on the thickness of the film. For an amorphous GdCo film with a thickness of 1000 angstrom the calculated K(u) is on the order of 10(3)-10(4) ergs/cm3. Dependence of K(u) on temperature and atomic concentration is also calculated.