3d magnetism in R2Fe14B compounds

An investigation of the magnetic properties of R2Fe14B compounds with R=Y, La, Ce, Gd, Lu and Th has been carried out. In all compounds the value of the Fe moment is in the range 2.0-2.2 μb, close to that of metallic Fe. This shows that effects of electron transfer and hybridization are weaker than in binary R-Fe compounds. The variation of the Curie temperatures of the different compounds is interpreted in terms of the dependence of the magnetic interactions on distance and on R. In all compounds, except Th2Fe14B, the temperature dependence of the anisotropy exhibits a maximum at T/Tc≅0.4. This effect is ascribed to competition between contributions from different Fe atomic sites and/or a change in the crystal field interactions associated with the magnetovolume anomaly which occurs in R2Fe14B compounds below Tc. (orig.)