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 perpendicular anisotropy in amorphous rare-earth--transition-metal films. The volume anisotropy energy density Kᵤ of this contribution depends inversely on the thickness of the film. For an amorphous GdCo film with a thickness of 1000 {} the calculated Kᵤ is on the order of 10³⁻⁻{10}⁴$ ergs ${cm}³$. Dependence of ${K}ᵤ$ on temperature and atomic concentration is also calculated.