On the origin of magnetic anisotropy in 4 f -free ferromagnets based on the CaCu 5 structure .

Using first-principles calculations, we investigate the origin of magnetocrystalline anisotropy in a series of 4 f -electron-free intermetallics with CaCu 5 -based structures: YCo 5 , YCo 4 B, and Y 3 Co 13 B 2 . The electronic structure of these compounds is characterized by a set of narrow 3 d bands near the Fermi level. In YCo 5 the easy-axis anisotropy originates primarily in the spin-orbit coupling-induced mixing of the electronic states with Codx2-y2anddxycharacter. The analysis of k -resolved anisotropy shows that positive contributions accumulate from the entire Brillouin zone but are particularly large near thekz=0plane. The analysis of the single-site and two-site terms reveals a large positive single-site contribution to the magnetocrystalline anisotropy from the Co atoms on the honeycomb sublattice, along with two-site contributions from both honeycomb and kagome sublattices.