Exchange interactions and Curie temperatures of the tetrametal nitrides Cr4N, Mn4N, Fe4N, Co4N, and Ni4N

TL;DR

This study calculates exchange interactions and Curie temperatures of five tetrametal nitrides with perovskite structure, revealing significant variation among them and providing insights into their magnetic properties.

Contribution

The paper provides the first detailed calculation of exchange interactions and Curie temperatures for Cr4N, Mn4N, Fe4N, Co4N, and Ni4N, highlighting their differences and explaining the low Curie temperature of Ni4N.

Findings

Curie temperatures range from 121K to 827K.

Exchange interactions vary markedly among the compounds.

The low Curie temperature of Ni4N is explained by exchange interactions.

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 naive 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 291K (Cr4N), 710K (Mn4N), 668K (Fe4N), 827K (Co4N), and 121K (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.