Spin current is the key element for nanoscale spintronic devices. For ultrafast operation of such nano-devices, generation of spin current in picoseconds, a timescale that is difficult to achieve using electrical circuits, is highly desired. Here we show thermally driven ultrafast demagnetization of a perpendicular ferromagnet leads to spin accumulation in a normal metal and spin transfer torque in an in-plane ferromagnet. The data are well described by models of spin generation and transport based on differences and gradients of thermodynamic parameters. The temperature difference between electrons and magnons is the driving force for spin current generation by ultrafast demagnetization. On longer timescales, a few picoseconds following laser excitation, we also observe a small contribution to spin current by a temperature gradient and the spin-dependent Seebeck effect.
Bibliographical noteFunding Information:
The development of TR-MOKE, thermal measurements and thermal modelling at the University of Illinois was supported by the US Department of Energy Office of Basic Energy Sciences under grant number DE-FG02-07ER46459. Measurements of thermally driven spin transport model were supported by the Army Research Office under grant number W911NF-11-10526. TR-MOKE and TDTR were carried out in the Laser and Spectroscopy Laboratory of the Materials Research Laboratory at the University of Illinois Urbana-Champaign. B.C.M. was supported by the Korea Institute of Science and Technology (KIST) institutional programme, the Pioneer Research Center Program of MSIP/NRF (2011-0027905) and the IT R&D programme of MOTIE/KEIT (10043398). B.C.M. acknowledges the technical assistance from Jung-Min Han at KIST. K.J.L. was supported by the NRF (NRF-2013R1A2A2A01013188) and KU-KIST School Joint Research Program. K.J.L. acknowledges M.D. Stiles for discussion.
Copyright 2014 Elsevier B.V., All rights reserved.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Physics and Astronomy(all)