Theoretical predictions of magnetic shape memory alloys in Gallium-rich Heusler compounds

This paper provides a comprehensive study of the structural, magnetic, electronic, vibrational, and bulk mechanical properties for Ga₂(Nb,Ta,W)X (X = Cr, Mn, Fe, Co, and Ni) Heusler alloys using first-principles density-functional theory. By considering the total energy, the structural type and magnetic configuration of cubic Ga₂(Nb,Ta,W)X are determined. Analyzing the calculated formation energies allows determination of the compounds that are stable electronically. The total energy difference between the austenite and martensite phases indicates that all the alloys are prone to tetragonal transitions from the austenite to martensite phases. Furthermore, the martensitic transitions are demonstrated from the perspectives of the density of states, phonon dispersion, mechanical stability criteria, and elastic anisotropy ratio. The ratio of the shear to bulk moduli indicates that all the considered Ga₂-based materials are inherently ductile, and most of the alloys possess much better ductility than the well-known Ni₂MnGa material. Among the considered alloys, Ga₂(Nb,Ta)X (X = Cr, Mn, and Fe) and Ga₂WX (X = Cr, Mn, Fe, and Co), which have martensitic transition temperatures above room temperature, are expected to operate as new magnetic shape memory alloys.