First-principles investigation of martensitic transformation and magnetic properties of Ni2XAl (X=Cr, Fe, Co) Heusler compounds

Abstract

The tetragonal distortion, magnetic and electronic properties of full Heusler compounds Ni2XAl (X = Cr, Fe, Co) have been studied by first-principles calculations based on density functional theory. The obtained lattice parameters, magnetic moments and bulk modulus are well consistent with available data of references. The ferromagnetic Ni2XAl compounds are more favorable than non-magnetic compounds. The resistance to volume deformation increases as the order of Ni2CrAl < Ni2FeAl < Ni2CoAl. Ni2CrAl have no tetragonal martensitic transformation and shape memory effect along Bain paths, but adjusting the stoichiometric ratio may lead to magnetic shape memory effect. Ni2CrAl are favorable in L21 austenite phase with magnetic moments of 3.503μB/f.u. Ni2FeAl and Ni2CoAl have austenite-to-martensite transformation existence, i.e., they have shape memory effect by applying external magnetic field and temperature. The corresponding lattice constants of L10 martensite phase are a = b = 5.211 Å, c = 6.983 Å and a = b = 5.109 Å, c = 7.051 Å, and magnetic moments are about 3.292μB/f.u. and 1.791μB/f.u., respectively. Finally, total and partial density of sates are analyzed to clarify the physical origin of Ni2XAl compounds, such as magnetism and phase transformation.