Dresden 2014 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 75: Focus Session: Spin-Orbit Torque at Surfaces and Interfaces (organized by MA)

TT 75.5: Topical Talk

Mittwoch, 2. April 2014, 17:15–17:45, BEY 118

Spin-orbit torques from first principles — •Frank Freimuth — Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany

Under application of electric currents, ferromagnetic (FM) layers asymmetrically sandwiched between nonmagnets (NM1, NM2) in NM1/FM/NM2 films are subject to spin-orbit torques (SOTs), which can serve to switch magnetization. Using density-functional theory calculations we study SOTs within the Kubo linear response formalism [1]. Comparing SOTs in NM1/FM films for different choices of NM1 (Pt, W, Ta, Ir, Ru, Au) we show that the sign of the spin Hall effect in these transition metals correlates with the even ("damping-like") component of SOT. Resolving torques and spin-fluxes on the atomic scale allows us to elucidate further the role of spin-currents in mediating the SOTs and to identify an additional spin-current independent component. Varying the thickness of Co and the choice of NM2 in NM2/Co/Pt(111) films we find a strong sensitivity of the odd ("field-like") component of SOT, while the even component is less sensitive. Estimating extrinsic contributions from a scalar disorder model [2] we argue that intrinsic effects prevail. We relate the intrinsic even SOT to the Dzyaloshinskii-Moriya interaction [3,4] and show that the intrinsic even SOT can be driven also by temperature gradients instead of electric currents.

[1] F. Freimuth et al., arXiv:1305.4873 [2] J. Weischenberg et al., PRL 107, 106601 (2011) [3] F. Freimuth et al., arXiv:1308.5983 [4] F. Freimuth et al., arXiv:1307.8085