Investigation of Optically Generated Spin-Currents in Pt/magnetic Insulator Bi-layered Structures

Pure spin current, which is important for novel spintronic devices, can be produced by spin Seebeck effect or by spin pumping. Recently, a new method was introduced for generating pure spin current directly by optically exciting a nanometer-thick Pt on YIG. Initial measurements using a broadband light source suggested that photogenerated electrons and holes generates a voltage in the Pt that is in proximity to YIG. Here we report the observation of a near-constant, optically created voltage due to spin current over a wide spectral range from 350 - 1600 nm. Despite strong spin-orbit coupling in Pt, we show that this signal is insensitive to the optical polarization and only depends on the optical power. Temperature, magnetic field, and time-dependent measurement are consistent with both the spin Seebeck and photo-spin-voltaic effects. These measurements show that pure spin currents can be optically generated in Pt/YIG heterostructures over a broad spectral range, which suggests their potential for implementation into a broadband photo-detection devices.