Volume magnetostriction of Fe-Ga alloys: calculation from first principles

In this paper, with the help of the density functional theory, the magnetic and magnetoelastic properties of the crystal structures A2 and D03 of Fe100-xGax alloys (x = 18-22 at.%) have been studied. The calculations were performed using the SPR-KKR software package. The exchange integrals, the values of the volume magnetoelastic constant B0, and the volume magnetostriction ΔV/V have been calculated. The obtained dependence of the exchange interaction constants on the crystal lattice parameter is a decreasing function for both A2 and D03 structures. It has been shown that the ferromagnetic interaction between iron atoms in the first coordination sphere increases with increasing Ga concentration in the fully disordered A2 phase, while this interaction weakens in the ordered crystal structure D03. The obtained values of ∆V/V for various compositions of Fe100-xGax alloys are negative. It is shown that an increase in the Ga content leads to an increase in volume magnetostriction for the A2 structure and a decrease in ∆V/V for the D03 phase. The character of the volume magnetostriction dependence on the concentration of Ga for structure A2 is consistent with the experimental data and with the results obtained for compounds based on Ni.