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 ${\mathit{K}}_{\mathit{u}}$ of this contribution depends inversely on the thickness of the film. For an amorphous GdCo film with a thickness of 1000 Å the calculated ${\mathit{K}}_{\mathit{u}}$ is on the order of ${10}^{3–}$ ${10}^4$ ergs ${\mathrm{cm}}^3$. Dependence of ${\mathit{K}}_{\mathit{u}}$ on temperature and atomic concentration is also calculated.