Curie Temperature of Sm₂Fe₁₇ and Nd₂Fe₁₄B: A First-Principles Study

摘要

We calculate intersite magnetic couplings for Sm2Fe17, Nd2Fe14, and Nd2Fe14X (X = B, C, N, O, F) using Liechtenstein's formula on the basis of first-principles calculation and analyze them to investigate the Curie temperature of Sm2Fe17 and Nd2Fe14B. We find that the magnetic coupling in the dumbbell bond is strongly ferromagnetic in our calculation, which is against a previous conjecture explaining the low Curie temperature for Sm2Fe17. The calculated values of the couplings explain the experimentally observed difference in the Curie temperature of Sm2Fe17 and Nd2Fe14B. We also address boron's effects on the Curie temperature of Nd2Fe14B, especially in connection with Kanamori's theory of cobaltization.