Spin-current across the metamagnetic transition in FeRh films as measured with THz emission spectroscopy*

THz emission from heterostructures of ferromagnetic (FM) and noble metal (NM) layers is attributed to spin-charge conversion at the FM/NM interface, yet similar effects in bare magnetic thin films are not fully understood. Here we perform THz emission spectroscopy on thin films of FeRh, which is well known to undergo an antiferromagnetic to ferromagnetic phase transition around room temperature. The emitted THz field is observed to have a strong temperature dependence and a power-law dependence on the incident pump pulse fluence. Combined with the knowledge of the spin Hall angle, we extract a temperature dependent spin current across the metamagnetic transition.