Spin-lattice couplings and their effects in transition-metal ferromagnets with ab-initio accuracy

In the emergent field of ultrafast magnetization dynamics, understanding the interplay between lattice, spin, and electrons is extremely relevant to the description of several phenomena. For systems with magnetic order, characterized by the existence of a collective motion of spins, both magnetic moments and lattice degrees of freedom are coupled via the electronic medium, which can influence, for instance, both magnon and phonon spectrum and lifetimes. Although a formalism to describe the magnetization dynamics accounting for the spin-lattice coupling (SLC) is known from many years ago [1], there is still a gap in the literature regarding the parameters for real materials, obtained with first-principles accuracy. From a theoretical point of view, this requires computing the magnetic interactions (e.g., Heisenberg exchange, Dzyaloshinskii-Moriya) in a broken inversion symmetry situation, making the use of real-space-based ab-initio methods a suitable way to calculate such parameters. The combination with state-of-the-art spin-lattice-dynamics simulations [2], then, make it possible to the investigate the influence of such SLC parameters in a wide range of materials.

In this talk, the results of spin-lattice calculations and their impact will be shown and discussed. We will consider the well-known ferromagnetic test cases (Fe, Co, Ni), but also - and more interestingly - systems in which the impact of SLC is greater due to significant changes in magnetic moments and/or interactions, such as Tb and Invar (Fe-Ni).

References:

[1] V. P. Antropov et al., Phys. Rev. B 54, 1019 (1996).

[2] J. Hellsvik et al., Phys. Rev. B 99, 104302 (2019).