Local ordering and interatomic bonding in magnetostrictive Fe_0.85Ga_0.15X (X=Ni,Cu,Co,La) alloy

The electronic structure of doped Fe–Ga alloy is investigated theoretically using methods of the density functional theory. The work aims to uncover the difference in the material's magnetostrictive properties when doping with transition metals or La as the simplest representative of rare-earth elements. The effect understudy was investigated by considering the change in two features of the electronic structure caused by doping: the density of d-states on Fe atoms and the nature of the Fe–Fe bonding near the doping atom. The transition metal atoms are surrounded by Fe atoms with a low-density d-states, eliminating the doping effect. The interatomic bonds of transition metals with the nearest Fe atoms have an antibonding character, while bonds between Fe atoms of the first and second coordination spheres are more binding than in an undoped alloy. This effect leads to magnetostriction decrease. In the La-doped alloy, the opposite picture is found. An increase in magnetostriction should occur due to the enhancement of the antibonding character of bonds between Fe atoms in the first and second coordination spheres of the dopant.