Exchange interactions and Curie temperature of Y-Co compounds

The Curie temperature of rare-earth Co intermetallics is investigated by self-consistent spin-polarized electronic-structure calculations on Y-Co compounds. The total exchange interaction of a given site with all other sites (J_o) is calculated by the linear-muffin-tin-orbital method using the local force theorem and employed to obtain mean-field Curie-temperature estimates. The theoretical predictions for YCo₃, YCo₅, and Y₂Co₁₇ are in fair agreement with the experimental Curie temperatures. For YCo₅, the variation of exchange interactions (J_ij) with distance is analyzed, and it is discussed how the presence of nonequivalent cobalt sites affects the Curie temperature of the compounds.