Dominik Legut
IT4Innovations, VSB – Technical University of Ostrava, Czech Republic

Magneto-crystalline anisotropy is one of the fundamental quantities for permanent magnets, but not only. The other example are magnetostriction and magnetoelastic effects. Utilizing the in-house developed approach the origin of the anisotropic magnetocrystalline energy (MAE) guided by the spin-orbit coupling (SOC) in the ordered Fe5Ta2 and L10-FePt phase is analyzed and discussed by means of theoretical calculations showing excellent agreement with the known experimental studies. A systematic analysis of the MAE, magnetostriction, and magnetoelasticity by means of first-principles plane-wave calculations and post-processing of calculated eigenvalues (orbital energies) and functions (orbital occupancies) are done to establish their correlations. Our study includes the convolution of the projected wave function (density of states) of each orbital of the Fe and Pt sub-lattices into orbital energies. The current novel technique shows the orbital contributions to MAE and magnetoelasticity in accordance with the plane-wave total energies including SOC, which have not been discussed earlier. We also explore the complete anisotropic magnetostriction of this material, finding a significant magnetostrictive (λ) performance of theorder about λ ∼ 10⁻⁴ − 10⁻³ in some particular crystallographic directions of the ordered crystal model, also known in the experiment. However, the poly-crystalline model of L10-FePt based on the uniform stress approximation, leads to a sharp decline in the overall magnetostrictive behaviour due to the linear combination of the single crystal magnetostrictive coefficients in the standard numerical techniques, leaving us with an explanation of the lower magnetostriction for polycrystalline thin-films as known also in the latest laboratory research.

More informations in following publications:
P. Nieves et al., Comp. Phys. Comm. 264, 107964 (2021).
P. Nieves et al., Comp. Phys. Comm. 271, 108197 (2022).
P. Nieves et al., Sensors, 20, 6436 (2020).
P. Nieves et al., Comp. Mater. Sci. 224, 112158 (2023).
S. Arapan et al., Phys. Rev. B 101, 014426 (2020).
T. Das et al., J. Phys. D: Appl. Phys. 58, 035004 (2025).
D. Legut and P. Nieves, Sol. St. Sci. (accepted)