Nernst thermopower in bismuth - ferromagnetic nanocomposites*

Magnetic materials in which thermal transport involves the generation of spin fluxes provide new opportunities to improve the thermal-to-electric energy conversion efficiency over that of conventional, electron-based thermoelectrics. In bulk ferromagnetic (FM) metals e.g. Co, Fe, and Ni, magnon dynamics result in a magnonic contribution to total thermopower, as shown by Watzman et al.¹ In thin-film structures composed of a normal metal (NM) film, e.g. Pt, deposited on an electrically insulating FM, e.g. yttrium iron garnet (YIG), a thermally driven spin flux injected from the FM into the NM layer gives rise to inverse spin-Hall voltage in the NM layer. Although these thin-film structures are not suitable for power generation, it was shown by Boona et al.² that it is possible to obtain a contribution from the spin-Seebeck effect (SSE) to the Nernst thermopower in bulk NM/FM nanocomposites. In this work, Bi will be used as a NM and Co as the FM. Bulk composites of Bi and Co nanoparticles will be studied to determine the SSE contribution to the Nernst thermopower.
(1) S.J. Watzman et al., Phys. Rev. B 94 (2016)
(2) S.R. Boona et al., Nat. Com. 7 (2016)