Exchange interactions in R2Fe14B and R2Fe14C compounds where R is a rare-earth

The exchange interactions in R2Fe14B and R2Fe14C compounds, where R is a rare-earth element, are analysed within the 4f-5d-3d model, using the data obtained from electronic structure calculations. The iron moments are dependent on site location and follow linear dependences on the De Gennes factor, with rates depending on their local environment. The contributions of local 4f-5d and 5d-3d short range interactions to the R5d band polarizations, M5d, are discussed. For a given series, the Curie temperatures of both the light and heavy rare-earths compounds follow the same dependence on the M5d values. The same trend is observed for the pseudo-ternary systems with substitution at the R site. The R5d band polarizations, M5d, reflect all changes in the magnetic properties when substitutions at the R and Fe positions are performed.