Tailoring magnetism at the nanometer scale in SmCo₅ amorphous films

The thickness dependence of magnetic properties has been studied in SmCo₅ amorphous films with imprinted in-plane anisotropy for thicknesses ranging down to the nanometer scale (2.5-100 nm). The field induced in-plane magnetic anisotropy decreases considerably when the film thickness is below 20 nm. Analysis of the magnetic anisotropy energy shows that the decrease of the induced in-plane anisotropy is accompanied by the development of an out-of-plane interface anisotropy. Two different regimes for the coercivity (H_c) change are found: below 3.75 nm, the H_c decreases continuously with decrease of the film thickness, whereas at above 3.75 nm, the H_c decreases with increase of the film thickness. This change in H_c can be understood by considering the decrease of the short range chemical order for the thinnest films (<3.75 nm) and the relative decrease of the interface contribution with increasing film thickness. The changes in anisotropy have a profound influence on the domain structure, in which the angle of the zigzag domain boundaries decreases with the inverse thickness of the layers.