Stability and magnetic properties of Nd6Fe13X (X = Al, Si, Cu, Zn, and Ga)

The stability and magnetic properties of the RE6Fe13X compounds, as well as their preferential localization in Nd-Fe-B magnets, have been investigated by first-principles calculations. We find that the RE6Fe13X (X = Al, Si, Zn, and Ga) have negative formation energies and are more likely to form in the triple junctions, while Nd6Fe13Cu with the formation energy of 0.73 eV tends to localize in the thin intergranular phase. These compounds contribute to the exchange decoupling of Nd2Fe14B grains and thus enhance the coercivity of Nd-Fe-B magnets. Such decoupling can be more pronounced in the cases of Nd6Fe13Cu and Nd6Fe13Zn, which exhibit antiferromagnetic ordering in the Fe sublattice according to our calculations. We propose that the partial substitution of Nd atoms with Pr can gradually reduce the formation energy of these phases and maintain their original antiferromagnetic states.