Importance of local structural distortions in magnetocaloric effect in Mn based antiperovskites

Abstract

Mn3GaC and Mn3SnC are two antiperovskites which exhibit a large magnetocaloric effect associated with a magnetostructural transformation. Although structurally similar, the magnetic transition and the nature of magnetocaloric effect in the two compounds is completely different. While Mn3GaC transforms from a ferromagnetic to an antiferromagnetic state at T-t = 178K with the antiferromagnetic propagation vector along k - 1/2, 1/2, 1/2, in Mn3SnC the transformation occurs at Tt = 280K from a paramagnetic state to an antiferromagnetic state with k - 1/2, 1/2, 0. Mn K EXAFS has been employed to show that these differences in magnetic properties are related to local structural distortions in Mn6C octahedra which are quite different in the two compounds.