Regensburg 2016 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 52: Focus: Ultrafast spin currents for spin-orbitronics: from metals to topological insulators

MA 52.5: Hauptvortrag

Freitag, 11. März 2016, 11:45–12:15, H32

Driving currents by magnetization dynamics in systems with broken inversion symmetry — •Frank Freimuth — Peter Grünberg Institut & Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany

By breaking the inversion symmetry in crystals, one switches on the correlation between axial and polar vectors, which otherwise would be forbidden by symmetry. In magnetic crystals one can thereby generate torques on the magnetization by applying electrical or heat currents, the so-called spin-orbit torques. Conversely, magnetization dynamics induces currents, which is the inverse spin-orbit torque effect. At small frequencies, i.e., under typical FMR conditions, the inverse spin-orbit torque can be understood in terms of spin pumping combined with the spin-Hall effect and the Rashba or Dresselhaus spin-orbit fields. However, when magnetic solids are excited by femtosecond laser pulses, additional effects set in, such as the generation of ultradiffusive spin-currents and ultrafast demagnetization, which lead to new mechanisms for generating electrical currents in inversion asymmetric magnets. Using the Kubo linear response formalism we systematically identify mechanisms behind the generation of electrical currents in the range from FMR up to optical frequencies, discovering also several new effects. In particular, we find that not only precession of magnetization, but also demagnetization, drive currents. Based on DFT calculations we investigate these effects in Co/Pt and Mn/W bilayers as well as in the half-Heusler compound PtMnSb and elucidate the role that spin-currents play.