Scaling of the spin Seebeck effect in bulk and thin film

Whilst there have been several reports of the spin Seebeck effect to date, comparison of the absolute voltage(s) measured, in particular for thin films, is limited. In this letter we demonstrate normalization of the spin Seebeck effect for Fe$_3$O$_4$:Pt thin film and YIG:Pt bulk samples with respect to the heat flux J$_q$, and temperature difference $\Delta$T. We demonstrate that the standard normalization procedures for these measurements do not account for an unexpected scaling of the measured voltage with area that is observed in both bulk and thin film. Finally, we present an alternative spin Seebeck coefficient for substrate and sample geometry independent characterization of the spin Seebeck effect.