Effect of Interstitial Atom Nitrogen on Properties of RE2Fe17 Compounds

The electronic structure and atomic magnetic moments of clusters NdFe6, NdFe6N3 and Fe8 with a dumbbell atom-pair in rare earth-transition element compounds NdEFe17Nx(x=0, 3) were studied by spin-polarized MS-Xα method. The results are as follows: There are three negative exchange couplings between Fe(c) and Fe(f) atoms in Nd2Fe17, which occur at their odd parity orbitals. Compared to the results of α-Fe calculated by the MS-Xα method, the low Curie temperature of compounds RE2Fe17 can be explained satisfactorily. (2) There is only one weaker negative exchange coupling orbital leaving in between Fe(c) and Fe(f) sites in Nd2Fe17N3. These results may be helpful for understanding the effect of interstitial atom M(M=N, H or C) in Fe2Fe17Mx on Curie temperature. The other key factors affecting the Fe-Fe exchange coupling in Fe2Fe17 compounds were also discussed.