Femtosecond photocurrents at the FeRh/Pt interface

Medapalli, R. and Li, G. and Patel, S.K.K. and Mikhaylovskiy, R.V. and Rasing, T. and Kimel, A.V. and Fullerton, E.E. (2020) Femtosecond photocurrents at the FeRh/Pt interface. Applied Physics Letters, 117 (14): 142406. ISSN 0003-6951

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Abstract

Femtosecond laser excitations of FeRh/Pt bilayers launch an ultrafast pulse of electric photocurrents in the Pt-layer and subsequently result in the emission of electromagnetic radiation in the THz spectral range. Analysis of the THz emission as a function of the polarization of the femtosecond laser pulse, external magnetic field, sample temperature, and sample orientation shows that the photocurrent can emerge due to vertical spin pumping and photo-induced inverse spin-orbit torque at the FeRh/Pt interface. The vertical spin pumping from FeRh into Pt does not depend on the polarization of light and originates from ultrafast laser-induced demagnetization of the ferromagnetic phase of FeRh. The photo-induced inverse spin-orbit torque at the FeRh/Pt interface can be described in terms of a helicity-dependent effect of circularly polarized light on the magnetization of the ferromagnetic FeRh and the subsequent generation of a photocurrent. © 2020 Author(s).