Electronic structure, magnetism and phase stability of isostructural Ga2MnCo-Ga2MnV Heusler alloys from first principles

The electronic structure, magnetism and phase stability of Ga2-based Heusler alloys Ga2MnCo and Ga2MnV are studied by first-principles calculations. The volume-conserving tetragonal distortions of the cubic Ga2MnCo and Ga2MnV show an energy minimum at c/a = 1.17 and 1.45, respectively. The isostructural alloying method is adopted to alloy two isostructures by substituting Co for V at density functional level. The calculations reveal that a potential tetragonal martensite phase can be expected with a large thermodynamic driving force and a moderate strain energy in Ga2MnCo-Ga2MnV system. For the middle composition of Ga2MnV0.5Co0.5, the energy difference between the martensite and parent phase reaches −140 meV/cell and the degree of distortion arrives at c/a = 1.275, which corresponds to a potential martensitic transformation. Based on the calculated results, the exchange interaction between Mn and V atoms is found to change from antiferromagnetic to ferromagnetic coupling with increasing c/a.