László Szunyogh

Understanding the mechanism driving magnetization switching in spin-orbit-torque-assisted devices remains a subject of debate. While originally attributed to the spin Hall effect and spin Rashba-Edelstein effect, recent discoveries related to orbital moments induced by the orbital Hall effect and the orbital Rashba-Edelstein effect have added complexity to the comprehension of the switching process in nonmagnet/ferromagnet bilayers. Addressing this challenge, we present a quantitative investigation of a Pt/Co bilayer by employing atomistic spin dynamics simulations, incorporating the proximity-induced moments of Pt, as well as electrically induced spin and orbital moments obtained from first-principles calculations. Our layer-resolved model elucidates the dampinglike and fieldlike nature of the induced moments by separating them according to their even and odd magnetization dependence. In addition to demonstrating that a larger fieldlike spin-orbit-torque contribution comes from previously disregarded induced orbital moments, our work highlights the necessity of considering interactions with Pt-induced moments at the interface, as they contribute significantly to the switching dynamics.

We determine the Dzyaloshinskii-Moriya interaction within and between two magnetic cobalt layers separated by a nonmagnetic spacer through calculations. We investigate different materials for the nonmagnetic layer, focusing on the experimentally realized Co/Ag/Co system. We laterally shift the atoms in the nonmagnetic layer to achieve the symmetry breaking required for the interlayer Dzyaloshinskii-Moriya interaction. We compare the resulting interactions with the Levy-Fert model and observe a good overall agreement between the model and the calculations for the dependence on the atomic positions. Additionally, we derive a formula for the strength of the interlayer isotropic exchange interaction depending on the position of the atoms in the nonmagnetic layer and compare it to the first-principles results. We investigate the limitations of the Levy-Fert model by turning off the spin-orbit coupling separately on the nonmagnetic and magnetic atoms and by studying the effect of band filling. Our work advances the understanding of the microscopic mechanisms of the interlayer Dzyaloshinskii-Moriya interaction and gives insight into possible new material combinations with strong interlayer Dzyaloshinskii-Moriya interaction. Published by the American Physical Society 2024

In this paper we present an ab initio scheme based on linear response theory of exchange torque correlation, implemented into the real-space Korringa-Kohn-Rostoker (RS-KKR) framework to calculate diagonal elements of the atomic-site-dependent intrinsic Gilbert damping tensor. The method is first applied to bcc iron and fcc cobalt bulk systems. Besides reproducing earlier results from the literature for those bulk magnets, the effect of the lattice compression is also studied for Fe bulk, and significant changes for the Gilbert damping are found. Furthermore, (001)-oriented surfaces of Fe and Co are also investigated. It is found that the on-site Gilbert damping increases in the surface atomic layer and decreases in the subsurface layer, and approaches the bulk value moving further inside the magnets. Realistic atomic relaxation of the surface layers enhances the identified effects. The first-neighbor damping parameters are extremely sensitive to the surface relaxation. Despite their inhomogeneity caused by the surface, the transverse Gilbert damping tensor components remain largely insensitive to the magnetization direction.