First-principles study of ferromagnetic Ni2CoGa(Zn) alloys in the Heusler and the inverse Heusler structure

Abstract

AbstractWe performed an ab initio characterization of ferro- and nonmagnetic Ni2CoGa and Ni2CoZn compounds with respect to their potential application as new ferromagnetic shape memory alloys. The calculation of structural energy differences and mixing energies in the common X2YZ Heusler structure and the inverse (XY)XZ structure revealed, that both alloys are stable in the tetragonal distorted Heusler structure with a c/a ratio of 1.38 and show ferromagnetic ordering. The Curie temperatures are of the order of ≃ 250 K. Exchanging Ga with Zn improves the magnetic properties of the alloy without qualitative modification of the structural energy landscape, but at the expense of a reduced mixing energy.