Ab Initio Study of the Structural Properties of the Co–Ni–Sn Heusler Alloys

The ab initio investigations of the structural and magnetic properties of the Co 2 Ni 1 + x Sn 1 – x ( x = 0, 0.25, 0.5, 0.75, 1) Heusler alloys are reported. The dependences of the total energy of the crystal structure on the degree of tetragonal distortions have been obtained and the most favorable crystal ordering has been established. The magnetocrystalline anisotropy energies for all the investigated compositions have been calculated. It is shown that all the compositions with the inverse Heusler structure are characterized by the easy-plane anisotropy, while in the regular Heusler structure the easy-plane anisotropy changes for easy-axis with the increasing Ni content. The highest anisotropy value has been found in the nonstoichiometric Co 2 Ni 1.5 Sn 0.5 and Co 2 Ni 1.75 Sn 0.25 compositions.