Speaker
Description
The origin of magnetocrystalline anisotropic energy (MAE) guided by spin-orbit coupling in the L1$_0$-FePt alloy was analyzed and the correlations among MAE and magnetoelastic (magnetostriction) constants $b^{\prime}𝑠$($\lambda^{\prime}𝑠$) by means of the electronic structure eigenvalues (orbital energies) and eigenfunctions (orbital occupancies) were established [1]. Our numerical analysis includes the convolution of the projected wave-function (density of states) of each orbital of the Fe and Pt sub-lattices into their orbital energies and its contribution to the MAE, $b^{\prime}𝑠$, and $\lambda^{\prime}𝑠$. However, this corresponds to the zero strain situation. For a zero stress (realistic conditions used in experiments) situtation a very small correction is found for the first anisotropy constant $\Delta K_1/K_1 = 0.07\%$, while a much more significant contribution is obtained for the second one $\Delta 𝐾_2/𝐾_2 = 21.86\%$. General analysis of this effect for tetragonal crystals is provided, finding that $\Delta 𝐾_1$ will be always positive for any stable phase with this symmetry [2]. We confront our magnetostriction coefficient with latest measurements for polycrystalline FePt.
Acknowledgements
The financial support of the projects QM4ST (CZ.02.01.01/00/22_008/0004572) by the Ministry of Education, Youth and Sports of the Czech Republic and No. 22-35410K of the Czech Science Foundation are acknowledged.
References
[1] T. Das et al., “Large magnetocrystalline anisotropic energy and its impact on magnetostriction of L10-FePt,” Journal of Physics D: Applied Physics, vol. 58, no. 3. IOP Publishing, p. 035004, Oct. 29, 2024. https://doi.org/10.1088/1361-6463/ad8001
[2] D. Legut, P. Nieves, "Second-order anisotropy due to magnetostriction for L1$_0$-FePt," Solid State Sciences, vol. 160. Elsevier BV, p. 107782, Feb. 2025. https://doi.org/10.1016/j.solidstatesciences.2024.107782
