Magnetic behavior of amorphous Sm-Co alloy films

Amorphous films of Sm_100–xCo_x with 70x90 were made by vapor deposition on flat glass substrates kept at 300 K. The films crystallize above 700 K. The film plane is the easy plane with the planar anisotropy of the order of 10⁷ erg cm^–3, indicating a local anisotropy of the order 10⁸ erg cm^–3. With regard to local anisotropy and magnetization, the films appear to correspond to the random anisotropy concept of amorphous magnets. Films evaporated in a magnetic field parallel to the film plane have an induced uniaxial anisotropy of the order of 10⁶ erg cm^–3. Hysteresis loops in fields parallel to the easy axis are perfectly rectangular with coercive fieldsH_c in the range 30 Oe<H_c<3000 Oe, depending on composition, temperature and heat treatment. The magnetization reverses by a thermally activated domain nucleation and growth process having a narrow distribution of time constants. Aging at temperatures below the crystallization temperature reduces the anisotropies andH_c.