Exploring the mechanism of the photo-excited spin currents in W/Y₃Fe₅O₁₂ heterostructure

The spin photovoltaic effect (SPVE) is anticipated to generate pure spin current under light in a contactless way. We systematically investigate the SPVE of Y₃Fe₅O₁₂ (YIG) with different thicknesses in W/YIG heterostructures under different laser wavelengths. The SPVE signal decreases with reducing the thickness of YIG (l_YIG) and it approaches to zero when l_YIG < 10 nm. In the representative W/YIG (350 nm) sample, the SPVE signal increases with increasing wavelength. Compared with short-wavelength laser, long-wavelength laser can maintain higher and more uniform energy distribution in YIG, thereby more efficiently exciting spin waves. Our results indicate that the SPVE is mainly dominated by the bulk mechanism rather than the interface mechanism induced by the magnetic proximity effects. This work offers a comprehensive analysis of the SPVE mechanism, laying a solid foundation for the development of SPVE prototype devices.