ELECTRONIC-STRUCTURE AND MAGNETIC-PROPERTIES OF Y-FE COMPOUNDS

A low concentration of rare earths (R) plays an important role in magn etic materials because of their large anisotropy. However, the Curie t emperature (T-C) has a decreasing trend with increasing Fe concentrati on 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-pola rized electronic structure calculations for the sequence YFe2-->YFe3-- >Y2Fe17-->YFe12 where yttrium is a prototype R element. The exchange i nteraction parameters are derived using the infinitesimal angle approa ch. The Monte Carlo simulations based on the Heisenberg Hamiltonian ar e 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 pro perties with Fe concentration are analyzed in terms of the local envir onment and magnetovolume effects.