First-Principles Study on the Role of B in Nd2Fe14B

Abstract

Rare-earth-Fe based magnetic compounds R2Fe17 (R = rare earth) are not capable of becoming strongmagnets due to their low Curie temperatures. Sagawa tried to make the ferromagnetism of thecompounds stronger through magneto-volume effect. He added boron (B) to Nd2Fe17 in order to stretchthe Fe-Fe distances, which led the discovery of Nd2Fe14B, the strongest magnet known[1]. However,according to the first-principles studies on (Y, Gd)2Fe14B with the same structure as Nd2Fe14B[2], themagnetic moment ms of Fe is reduced after adding B, implying that B does not enhance the magneticproperties of Nd2Fe14B. We perform first-principles calculations for Nd2Fe14B in order to understand the role of B in terms ofms, magnetization, and stability. From our analysis, we find that B does not work effectively on improvingthe ms and magnetization of Nd2Fe14B, because the total magnetic moment of Fe is reduced by addingB. We also calculated the formation energies of Nd2Fe14X, where X represents B, C, N, O, and F. Theobtained formation energies are consistent with experimental results.[1] M. Sagawa et al., J. Appl. Phys. 55, 2083 (1984).[2] M. Yamaguchi and S. Asano, Physica B: Cond. Matt. 254, 73 (1998).