The photothermoelectric (PTE) effect that originates from the temperature difference within thermoelectric materials induced by light absorption can be used as the mechanism for a light sensor in optoelectronic applications. In this work, a PTE-based photodetector is reported using a spin thermoelectric structure consisting of CoFeB/Pt metallic bilayers and its signal enhancement achieved by incorporating a plasmonic structure consisting of Au nanorod arrays. The thermoelectric voltage of the bilayers markedly increases by 60 ± 10% when the plasmon resonance condition of the Au nanorods is matched to the wavelength of the incident laser. Full-wave electromagnetic simulations reveal that the signal enhancement is due to the increase in light absorption and consequential local heating. Moreover, the alignment of the Au nanorods makes the thermoelectric voltages sensitive to the polarization state of the laser, thereby enabling the detection of light polarization. These results demonstrate the feasibility of a hybrid device utilizing plasmonic and spin-thermoelectric effects as an efficient PTE-based photodetector.

The spin thermoelectric effect, an electric voltage generation by a thermal spin current in magnetic systems, has been investigated as a candidate for thermal energy harvesting, but its thermoelectric conversion efficiency has to be enhanced further for practical applications. In this study, we demonstrate the amplification of spin thermoelectric signals by forming a spin thermopile consisting of exchange biased Pt/CoFeB multilayers. When the Pt is thinner than 3 nm, the Pt/CoFeB multilayer behaves like a single ferromagnet, of which the magnetization direction is controlled through exchange coupling with an adjacent antiferromagnet IrMn. This enables the fabrication of spin thermopiles with the Pt/CoFeB magnetic multilayers, in which the thermoelectric signal increases in proportion to the numbers of multilayers and wire elements of the thermopile. This scalability in the thermoelectric signal of the multilayer spin thermopile opens the way for energy harvesting on the basis of the spin thermoelectric effect.