Femtosecond laser excitation of FeRh/Pt bilayers launches an ultrafast pulse of electric photocurrent in the Pt-layer and thus results in emission of electromagnetic radiation in the THz spectral range. Analysis of the THz emission as a function of polarization of the femtosecond laser pulse, external magnetic field, sample temperature and sample orientation shows that 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 to 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 subsequent generation of a photocurrent.
@article{arxiv.2005.13379,
title = {Femtosecond Photocurrents at the Pt/FeRh Interface},
author = {Rajasekhar Medapalli and Guanqiao Li and Sheena K. K. Patel and Rostislav. V. Mikhaylovskiy and Theo Rasing and Alexey V. Kimel and Eric E. Fullerton},
journal= {arXiv preprint arXiv:2005.13379},
year = {2020}
}