Regensburg 2022 – scientific programme

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MA: Fachverband Magnetismus

MA 21: Terahertz Spintronics

MA 21.9: Talk

Wednesday, September 7, 2022, 11:30–11:45, H43

Transition of laser-induced terahertz spin currents from torque- to conduction-electron-mediated transport — •Oliver Gueckstock¹, Pilar Jimenez-Cavero^1,2, Lukas Nadvornik¹, Irene Lucas², Tom S. Seifert¹, Luis Morellon², and Tobias Kampfrath¹ — ¹FU Berlin, Germany — ²Universidad de Zaragoza, Spain

Transport of spin angular momentum is a fundamental operation required for future spin-electronic devices. To be competitive with other information carriers, it is required to push the bandwidth of spin transport to the terahertz (THz) frequency range [1]. Here, we use femtosecond laser pulses to excite prototypical F|N bilayers consisting of a ferrimagnetic metal F and a nonmagnetic metal N [2,3]. Following absorption of the pulse, a spin current in F is launched and converted into a transverse charge current in N, giving rise to the emission of a THz electromagnetic pulse [2]. Depending on the conductivity of F, two driving mechanisms of the spin current can occur: (i) the ultrafast spin Seebeck effect [3] generating magnons and (ii) a spin voltage, generating a spin current carried by conduction electrons [4]. Remarkably, in the half-metallic ferrimagnet Fe3O4, we observe the coexistence of these contributions and disentangle them based on their distinctly different ultrafast dynamics. Our results shed new light on the magnetic structure of this mature material. References: [1] Vedmedenko et al., J. Phys. D: Appl. Phys. 53 453001 (2020), [2] T. Seifert et al., Nat. Phot. 10, 483 (2016), [3] T. Seifert et al., Nat. Comm. 9, Article No: 2899 (2018), [4] R. Rouzegar et al., arXiv:2103.11710 (2021)