Terahertz spectroscopy for all-optical spintronic characterization of the spin-Hall-effect metals Pt, W and Cu80Ir20

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