Amplification of Spin Thermoelectric Signals in Multilayer Spin Thermopiles

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.