On the origin of magnetic anisotropy in 4f -free ferromagnets based on the CaCu5 structure.

Using first-principles calculations, we investigate the origin of magnetocrystalline anisotropy in a series of
4f -electron-free intermetallics with CaCu5-based structures: YCo5, YCo4B, and Y3Co13B2. The electronic
structure of these compounds is characterized by a set of narrow 3d-bands near the Fermi level. In YCo5
the easy-axis anisotropy originates primarily in the spin-orbit coupling-induced mixing of the electronic states
with Co dx2-y2 and dxy character. The analysis of k-resolved anisotropy shows that positive contributions
accumulate from the entire Brillouin zone but are particularly large near the kz = 0 plane.
The analysis of the single-site and two-site terms reveals a large positive single-site contribution to the mag-
netocrystalline anisotropy from the Co atoms on the honeycomb sublattice, along with two-site contributions
from both honeycomb and kagome sublattices.