Authors:	Jimenez-Cavero, Pilar Gueckstock, Oliver Nádvorník, Lukáš Lucas, Irene Seifert, Tom S. Wolf, Martin Rouzegar, Reza Brouwer, Piet W. Becker, Sven Jakob, Gerhard Kläui, Mathias Guo, Chenyang Wan, Caihua Han, Xiufeng Jin, Zuanming Zhao, Hui Wu, Di Morellón, Luis Kampfrath, Tobias
Title:	Transition of laser-induced terahertz spin currents from torque- to conduction-electron-mediated transport
Online publication date:	1-Aug-2022
Year of first publication:	2022
Language:	english
Abstract:	Spin transport is crucial for future spintronic devices operating at bandwidths up to the terahertz range. In F|N thin-film stacks made of a ferromagnetic/ferrimagnetic layer F and a normal-metal layer N, spin transport is mediated by (1) spin-polarized conduction electrons and/or (2) torque between electron spins. To identify a crossover from (1) to (2), we study laser-driven spin currents in F|Pt stacks where F consists of model materials with different degrees of electrical conductivity. For the magnetic insulators yttrium iron garnet, gadolinium iron garnet (GIG) and γ -Fe2O3, identical dynamics is observed. It arises from the terahertz interfacial spin Seebeck effect (SSE), is fully determined by the relaxation of the electrons in the metal layer, and provides a rough estimate of the spin-mixing conductance of the GIG/Pt and γ -Fe2O3/Pt interfaces. Remarkably, in the half-metallic ferrimagnet Fe3O4 (magnetite), our measurements reveal two spin-current components with opposite direction. The slower, positive component exhibits SSE dynamics and is assigned to torque-type magnon excitation of the A- and B-spin sublattices of Fe3O4. The faster, negative component arises from the pyrospintronic effect and can consistently be assigned to ultrafast demagnetization of minority-spin hopping electrons. This observation supports the magneto-electronic model of Fe3O4. In general, our results provide a route to the contact-free separation of torque- and conduction-electron-mediated spin currents.
DDC:	530 Physik 530 Physics
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 08 Physik, Mathematik u. Informatik
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-7464
Version:	Published version
Publication type:	Zeitschriftenaufsatz
Document type specification:	Scientific article
License:	CC BY
Information on rights of use:	https://creativecommons.org/licenses/by/4.0/
Journal:	Physical review : B 105 18
Pages or article number:	184408
Publisher:	American Physical Society
Publisher place:	Ridge, NY
Issue date:	2022
ISSN:	2469-9950
Publisher DOI:	10.1103/PhysRevB.105.184408
Appears in collections:	JGU-Publikationen