Spin Seebeck effect in Pt/SrMnO₃ heterostructures

Spin Seebeck effect (SSE) is one of the effective ways of generating pure spin currents driven by thermal gradients and has been extensively explored in spin caloritronics, an active branch in spintronics. In recent years, the focus has shifted to antiferromagnetic insulators (AFM-I), where spin currents created by a thermal gradient has been studied. Thermal gradients across the AFM-I film produce pure spin currents in an adjacent heavy metal layer such as platinum (Pt) due to non-equilibrium distribution of thermal magnons. These spin currents can be detected as a transverse charge current across the Pt layer via inverse spin Hall effect. Here, we have performed systematic investigations of SSE employing two measurement geometries, local and non-local configurations, on oxygen (non-)stoichiometric-SrMnO₃ thin films, which exhibit weak-ferromagnetic, insulating behavior down to low temperatures. Controlled experiments as a function of the applied dc bias, magnitude and orientation of applied magnetic field were used to disentangle the role of possible magnetic proximity effects. We observe a quadratic dependence of the SSE signal in Pt/SrMnO₃ with the applied current density. SSE is an important tool to detect and study magnon transport in hitherto unexplored complex oxides.