title: Spin current generated by thermally driven ultrafast demagnetization.
abstract: 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.
authors.affiliation: 1] Department of Materials Science and Engineering, and Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1304 West Green Street, Urbana, Illinois 61801, USA [2] Center for Spintronics Research, Korea Institute of Science and Technology, Seoul 136-791, Korea.
authors.forename: Gyung-Min
authors.initials: GM
authors.lastname: Choi
authors.affiliation: Center for Spintronics Research, Korea Institute of Science and Technology, Seoul 136-791, Korea.
authors.forename: Byoung-Chul
authors.initials: BC
authors.lastname: Min
authors.affiliation: Department of Materials Science and Engineering and KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 136-701, Korea.
authors.forename: Kyung-Jin
authors.initials: KJ
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering, and Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1304 West Green Street, Urbana, Illinois 61801, USA.
authors.forename: David G
authors.initials: DG
authors.lastname: Cahill