Spin Seebeck effect in antiferromagnet nickel oxide in wide ranges of temperature and magnetic field

In the spin Seebeck effect (SSE), the spin currents generated by thermal gradients applied to a magnetic film are detected by an electric voltage along an adjacent metallic layer due to the spin to charge current conversion through the inverse spin Hall effect. The SSE has been widely studied in bilayers made of insulating ferro- or ferrimagnet insulators and metals with large spin-orbit coupling such as platinum. Few studies of the SSE have been reported in antiferromagnetic insulators despite the increasing attention these materials have been receiving in the field of antiferromagnetic spintronics. Here we report an investigation of the SSE in bilayers made of well-textured polycrystalline films of antiferromagnetic NiO with platinum in a wide range of temperatures and magnetic fields. We demonstrate that the SSE is detected only when the NiO layer is fabricated with a Py underlayer to induce a macroscopic antiferromagnetic arrangement. The results are in good qualitative agreement with a drift-diffusion magnonic theory developed for single-crystal NiO.