  We report a systematic study on the thermoelectric performance of spin
Seebeck devices based on Fe3O4/Pt junction systems. We explore two types of
device geometries: a spin Hall thermopile and spin Seebeck multilayer
structures. The spin Hall thermopile increases the sensitivity of the spin
Seebeck effect, while the increase in the sample internal resistance has a
detrimental effect on the output power. We found that the spin Seebeck
multilayers can overcome this limitation since the multilayers exhibit the
enhancement of the thermoelectric voltage and the reduction of the internal
resistance simultaneously, therefore resulting in significant power
enhancement. This result demonstrates that the multilayer structures are useful
for improving the thermoelectric performance of the spin Seebeck effect.
