Dresden 2017 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 23: Spin Dynamics and Transport: Ultrafast Effect
MA 23.8: Vortrag
Dienstag, 21. März 2017, 11:30–11:45, HSZ 403
Ultrafast Spin Transfer Torque Generated by a Femtosecond Laser Pulse — •Pavel Baláž1, Martin Žonda1, Karel Carva1, Pablo Maldonado2, and Peter Oppeneer2 — 1Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, CZ-12116 Prague 2, Czech Republic — 2Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
A phenomenon of laser pulse-induced ultrafast demagnetization of magnetic material on femtosecond time-scale, is connected with number of open questions. Particularly, in transition metals and their alloys featuring spin polarized 3d valence band and conduction 4s band, a laser pulse can excite electrons from the d band into the s one with higher electron mobility. Consequently, the nonequilibrium hot charge carriers migrate away from the laser spot and reduce the local magnetic moment. This process is described by the superdiffusive spin transport model [1], which takes into account scattering of hot electrons on atomic sites leading to nonequilibrium avalanches of excited electrons.
In this work, we study the spin transfer torque and magnetization dynamics induced by a spin current of hot electrons in spin valve consisted of two magnetic layer with perpendicular magnetizations separated by a nonmagnetic one. To this end, we developed a four-channel model of spin transport, which allows us to calculate spin transfer torque and describe magnetization dynamics.
[1] M. Battiato, K. Carva, P. Oppeneer Phys. Rev. Lett. 105, 027203 (2010); Phys. Rev. B 86, 024404 (2012).