Quantitative temperature dependence of the Spin Seebeck effect in a mixed valent manganite*

Spin Seebeck effect offers a pure spin current under the application of a thermal gradient across a magnetic material and has become an active area of research in the field of spin caloritronics. Here, we report on the temperature dependence of the longitudinal spin Seebeck effect (LSSE) in the mixed valent manganite La_0.7Ca_0.3MnO₃. By disentangling the contribution arising due to the anomalous Nernst effect, we observe that in the low-temperature regime, the LSSE exhibits a T^0.5 dependence, which matches well with that predicted by the magnon-driven spin current model. Across the double exchange driven paramagnetic-ferromagnetic transition, the LSSE exponent is significantly higher than the magnetization one and also depends on the thickness of the spin-to-charge conversion layer. These observations highlight the importance of individually ascertaining the temperature evolution of different mechanisms — especially the spin mixing conductance — which contribute to the measured spin Seebeck signal.