Effect of Rare-Earth Element Doping on Fe-Ga Alloys Properties: Ab Initio and Monte Carlo Modelling

In this paper, we study the effect of a small addition of rare earth elements on the structural, magnetic, and magnetomechanical properties of Fe 80,47 Ga 18,75 RE 0,78 alloys (RE = Tb, Pr, Er) in the D0 3 phase using the density functional theory and the Monte Carlo method.Geometrical optimization of the crystal lattice performed on a 128-atom supercell showed that one RE substitution atom leads to an increase in the volume per atom of the cell by ≈ 1%.It is shown that Fe 80,47 Ga 18,75 RE 0,78 alloys are mechanically stable, however a significant decrease in C ′ is observed.The addition of RE atoms has a significant effect on the magnetic anisotropy of the alloy and changes the direction of the easy axis from [001] to [111] compared to Fe 81,25 Ga 18,75 .The highest value of tetragonal magnetostriction λ 001 ≈ -179 × 10 -6 is found in the Fe 80,47 Ga 18,75 Tb 0,78 alloy.The calculated value of the Curie temperature in compositions containing RE is ≈ 200 K lower than that of Fe 81,25 Ga 18,75 , and the lowest value is found in the Fe 80,47 Ga 18,75 Er 0,78 alloy.This behavior is due to the presence of antiferromagnetic exchange interactions between Er and Fe atoms in the first and second coordination spheres.