Structural, electronic and magnetic properties of Ni2XAl (X= V, Cr, Mn, Fe, and Co) Heusler alloys: An ab initio study

Abstract

Nickel-based Ni2XAl (X ​= ​V, Cr, Mn, Fe, and Co) Heusler alloys for both L21 and L10 crystal structures are studied by using the density functional theory. The magnetization energy and formation energy of Ni2XAl Heusler alloys are calculated. We found that in the ideal L21 structure, ferromagnetic (FM) state is more stable than nonmagnetic (NM) and antiferromagnetic (AF) states, except Ni2VAl. The ground state for Ni2VAl is the nonmagnetic state. The so-called Bain paths method is applied to study the stability of Ni2XAl alloys under tetragonal distortion. We found that Ni2FeAl and Ni2CoAl are possible ferromagnetic shape materials (FSMs). We also found that Ni2CrAl and Ni2CoAl are energetically favorable in the antiferromagnetic state in the L10 structure. To study the stability between L21 and L10 crystal structure, we calculate the cohesive energy for comparison. We also calculate the elastic constants, bulk modulus, shear modulus, and universal elastic anisotropy to study the mechanical stability in L21 and L10 crystal structure. The spin polarization for the L21 structure is calculated whilst the largest spin polarization is smaller than 80%.