Transition of laser-induced terahertz spin currents from torque- to conduction-electron-mediated transport

Jimenez-Cavero P, Gueckstock O, Nadvornik L, Lucas I, Seifert TS, Wolf M, Rouzegar R, Brouwer PW, Becker S, Jakob G, Klaeui M, Guo C, Wan C, Han X, Jin Z, Zhao H, Wu D, Morellon L, Kampfrath T (2022)

Publication Type: Journal article

Publication year: 2022

Journal

Physical Review B American Physical Society

Book Volume: 105

Article Number: 184408

Journal Issue: 18

DOI: 10.1103/PhysRevB.105.184408

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.

Involved external institutions

Freie Universität Berlin DE Germany (DE) University of Chinese Academy of Sciences CN China (CN) Universidad de Zaragoza ES Spain (ES) Johannes Gutenberg-Universität Mainz (JGU) DE Germany (DE) University of Shanghai for Science and Technology (USST) CN China (CN) Nanjing University CN China (CN) Fritz-Haber-Institut der Max-Planck-Gesellschaft (FHI) DE Germany (DE)

How to cite

APA:

Jimenez-Cavero, P., Gueckstock, O., Nadvornik, L., Lucas, I., Seifert, T.S., Wolf, M.,... Kampfrath, T. (2022). Transition of laser-induced terahertz spin currents from torque- to conduction-electron-mediated transport. Physical Review B, 105(18). https://dx.doi.org/10.1103/PhysRevB.105.184408

MLA:

Jimenez-Cavero, Pilar, et al. "Transition of laser-induced terahertz spin currents from torque- to conduction-electron-mediated transport." Physical Review B 105.18 (2022).

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