Electronic structure and magnetic properties of Y-Fe compounds

A low concentration of rare earths (R) plays an important role in magnetic materials because of their large anisotropy. However, the Curie temperature (T-C) has a decreasing trend with increasing Fe concentration in R-Fe compounds. In order to understand the variation of T-C as a function of iron concentration we carry out self-consistent spin-polarized electronic structure calculations for the sequence YFe2-->YFe3-->Y2Fe17-->YFe12 where yttrium is a prototype R element. The exchange interaction parameters are derived using the infinitesimal angle approach. The Monte Carlo simulations based on the Heisenberg Hamiltonian are carried out to derive T-C of Y-Fe compounds and results are in very good agreement with experimental data. The changes in the magnetic properties with Fe concentration are analyzed in terms of the local environment and magnetovolume effects.