First-principles study of intersite magnetic couplings in NdFe${}_{12}$ and NdFe${}_{12}$X (X = B, C, N, O, F)

Abstract

We present a first-principles investigation of NdFe${}_{12}$ and NdFe${}_{12}$X (X = B, C, N, O, F) crystals with the ThMn${}_{12}$ structure. Intersite magnetic couplings in these compounds, so-called exchange couplings, are estimated by Liechtenstein's method. It is found that the Nd--Fe couplings are sensitive to the interstitial dopant X, with the Nd--Fe(8j) coupling in particular reduced significantly for X = N. This suggests that the magnetocrystalline anisotropy decays quickly with rising temperature in the X = N system although nitrogenation has advantages over the other dopants in terms of enhancing low-temperature magnetic properties. The Curie temperature is also calculated from the magnetic couplings by using the mean field approximation. Introduction of X enhances the Curie temperature, with both structural changes and chemical effects found to play important roles in this enhancement.

18 pages, 11 figures; data added to Appendix sections

References in corpus (2)

• Standard model of the rare-earths, analyzed from the Hubbard I approximation
• Monte Carlo analysis for finite temperature magnetism of Nd${}_2$Fe${}_{14}$B permanent magnet

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