LAUSR

We present a comprehensive study of the temperature (T) dependence of the longitudinal spin Seebeck effect (LSSE) in Pt/EuO1-x and Pt/La2NiMnO6 (LNMO) hybrid structures across their Curie temperatures (T-c). Both systems host ferromagnetic interaction below T-c, and hence present optimal conditions for testing magnon spin current based theories against ferrimagnetic yttrium iron garnet. Notably, we observe an anomalous Nernst effect generated voltage in bare EuO1-x, however, we find LSSE predominates the thermal signals in the bilayers with Pt. The T dependence of the LSSE in small T range near T-c could be fitted to a power law of the form (T-c- T)(p). The derived critical exponent P was verified for different methods of LSSE representation and sample crystallinity. The results are explained based on the magnon-driven thermal spin pumping mechanism that relates the T dependence of LSSE to the spin mixing conductance (G(mix)) at the heavy metal/ferromagnet interface, which in turn is known to vary inaccordance with the square of the spontaneous magnetization (M-s). Additionally, the T dependence of the real part of G(mix) derived from spin Hall magnetoresistance measurements at different temperatures for the Pt/LNMO structure further establishes the interdependence.