Magnetism-Driven Negative Thermal Expansion of Inverse-Perovskite Type Antiferromagnets

Abstract

This article overviews recent theoretical work that explored a mechanism of the magnetism-induced negative thermal expansion (NTE) observed in inverse-perovskite antiferromagnets Mn₃ AN ( A=Zn, Ga, etc). These compounds exhibit crystal-volume expansion upon cooling, triggered by a non-coplanar antiferromagnetic order. In spite of intensive studies, however, the mechanism has been remained as a puzzle for 50 years. This puzzle was recently solved by considering microscopic electronic and magnetic structures and couplings between magnetism and the crystal lattice in real materials. The clarified mechanism turned out to be applicable to even magnets with crystal structures other than the inverse-perovskite. Hence, the work provides important guiding principles to research for new NTE materials and will contribute to the development of this research field.