An amorphous thin magnetic film having stabilized uniaxial anisotropy of thickness 200-1000 angstroms is fabricated from an alloy of composition CoX where X is one of the elements Zr, Nb, Mo, Ta, Ru, Rh, Pd, Hf, Ti, W, Re, Os, Ir. The invention teaches setting the magnitude of the uniaxial anisotropy of the film at a predetermined magnitude and stabilizing the anisotropy against long term change through (1) the addition of controlled amounts of silicon to the alloy, (2) cladding each face of the film with an Si02 layer, and (3) stabilizing and annealing the resultant clad film in a two step process.