Mathematical Modelling

Effect of rare-earth element doping on Fe–Ga alloys properties: ab initio and Monte Carlo modelling

M. V. Matyunina, A. S. Sokol, О. O. Pavlukhina, M. A. Zagrebin, V. V. Sokolovskiy, V. D. Buchelnikov

Chelyabinsk State University, Chelyabinsk, Russian Federation

Abstract: 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 $\approx 1$%. 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 $\left[001\right]$ to $\left[111\right]$ compared to Fe$_{81,25}$Ga$_{18,75}$. The highest value of tetragonal magnetostriction $\lambda_{001}\approx-179\times 10^{-6}$ 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 $\approx 200$ 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.

Keywords: magnetostriction, Fe-Ga alloys, density functional theory, rare earth elements.

UDC: 537.9+537.634.2

MSC: 82B26

Received: 06.12.2024

Language: English

DOI: 10.14529/mmp250202