  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.
