Terahertz spectroscopy for all-optical spintronic characterization of the spin-Hall-effect metals Pt, W and Cu${}_{80}$Ir${}_{20}$

Abstract

Identifying materials with an efficient spin-to-charge conversion is crucial for future spintronic applications. The spin Hall effect is a central mechanism as it allows for the interconversion of spin and charge currents. Spintronic material research aims at maximizing its efficiency, quantified by the spin Hall angle ${\Theta }_{\text{SH}}$ and the spin-current relaxation length ${\lambda }_{\text{rel}}$. We develop an all-optical method with large sample throughput that allows us to extract ${\Theta }_{\text{SH}}$ and ${\lambda }_{\text{rel}}$. Employing terahertz spectroscopy, we characterize magnetic metallic heterostructures involving Pt, W and Cu${}_{80}$Ir${}_{20}$ in terms of their optical and spintronic properties. We furthermore find indications that the interface plays a minor role for the spin-current transmission. Our analytical model is validated by the good agreement with literature DC values. These findings establish terahertz emission spectroscopy as a reliable tool complementing the spintronics workbench.

Article for Special Issue on Spincaloritronic in the Journal of Physics D