The Effect of Doping with Al on the Stability of D03 and L12 Phases in Fe73.44(Ga,Al)26.56 Alloys: Ab Initio Calculation and Monte Carlo Modeling

The effect of doping with Al on the stability of D03 and L12 phases was studied in the magnetostriction Fe–Ga and Fe–Ga–Al alloys with a high content of nonmagnetic atoms of ≈27 at %. For the studied D03 and L12 structures, the tetragonal shear modules C' = (C11 – C12)/2 and the Debye temperatures ΘD were found by the methods of density functional theory. The replacement of 4.58 at % of Ga by Al atoms was shown to lead to an increase in ΘD and a decrease in C′. Using the combined approach ab initio and Monte Carlo modeling, the calculations of free energies were performed, and the D03–L12 phase transition temperatures were determined. The Al addition to the Fe–Ga system was shown to decrease the difference between the energies of the D03 and L12 structures.