title: Exchange interactions and Curie temperatures of the tetrametal nitrides Cr₄N, Mn₄N, Fe₄N, Co₄N, and Ni₄N.
abstract: The exchange interactions of Cr4N, Mn4N, Fe4N, Co4N, and Ni4N compounds with perovskite structure were calculated to obtain the Curie temperatures for these compounds from Monte Carlo calculations. Contrary to naíve expectation, the exchange interactions vary markedly among these five compounds. In Fe4N, the intra-sublattice interaction of the Fe 3c atoms is strongly negative, leading to a significant reduction of the Curie temperature. The calculated Curie temperatures are 291 K (Cr4N), 710 K (Mn4N), 668 K (Fe4N), 827 K (Co4N), and 121 K (Ni4N), in good agreement with experimental observations where available. The much lower Curie temperature of Ni4N compared to fcc Ni is explained on the basis of the exchange interactions.
authors.affiliation: Center for Spinelectronic Materials and Devices, Bielefeld University, 33501 Bielefeld, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Meinert