Femtosecond Photocurrents at the Pt/FeRh Interface

Direct and inverse spin-orbit torques in antiferromagnetic and ferromagnetic FeRh/W(001)

“…In Ref. [18,19] a helicity-dependent THz signal was measured in FeRh/Pt after illumination with a fs laserpulse, which can be explained by the model described in Ref. [37].…”

“…Assuming that L precesses around the z axis according to L(t) = [sin(θ) cos(ωt), sin(θ) sin(ωt), cos(θ)] T (18) at the antiferromagnetic resonance, we obtain from Eq. ( 13) the current densities…”

“…The inverse SOT [24,25] describes the electric current induced by magnetization dynamics and is therefore related to vertical spin pumping, which has been investigated experimentally in the similar system of FeRh/Pt [16]. The inverse SOT is also related to the helicity-dependent component of the THz signal that follows excitation by a fs laser-pulse, and which was measured experimentally in FeRh/Pt as well [18,19]. For comparison we compute the SOTs also in an Fe monolayer on W(001), which exhibits a c(2 × 2) AFM configuration [26] and is therefore compensated like FeRh.…”

“…Lateral spin-pumping between FM and AFM domains has been found to be crucial for the damping enhancement [16]. When FeRh/Pt is excited by femtosecond laser pulses superdiffusive spin currents are generated in FeRh and converted into a charge current by the inverse spin Hall effect, which leads to a measurable THz signal [17][18][19]. This THz signal varies strongly as FeRh goes through the AFM-FM phase transition because it is suppressed in the AFM state of FeRh.…”