Thermodynamic Stability of ThMn$_{12}$-type CeFe$_{8}$M$_{4}$ Magnetic Compounds

Rare earth (R) elements such as Nd and Dy are critical constituents of high-performance Nd$_{2}$Fe$_{14}$B-type permanent magnets. Ongoing economic uncertainties have stimulated great interest in magnets that use alternative R materials, Ce in particular since it is the most abundant R element. While the intrinsic magnetic properties of known Ce-based compounds are inferior to those of their Nd-based cognates, they nevertheless offer the prospect of developing magnets with technical characteristics intermediate between those of Nd-Fe-B and ferrites. Moreover, there is ample opportunity to identify novel Ce systems. As a means of guiding the synthesis of new CeFe$_{\mathrm{12-x}}$M$_{\mathrm{x}}$ phases we have assessed the thermodynamic stability of ThMn$_{12}$-type CeFe$_{8}$M$_{4}$ compounds with 26 different elements M via density functional calculations. Compounds of this class are attractive since they can have larger Fe:R ratios than R$_{2}$Fe$_{14}$B, and in some cases additional processing such as nitriding, hydriding, or carbiding can substantially improve the magnetic properties. We critically compare the theoretical results with experiment.