  We investigate the relation between thermal spin-transfer torque (TSTT) and
the spin-dependent Seebeck effect (SDSE), which produces a spin current when a
temperature gradient is applied across a metallic ferromagnet, in nanopillar
metallic spin valves. Comparing its angular dependence (aSDSE) with the angle
dependent magnetoresistance (aMR) measurements on the same device, we are able
to verify that a small spin heat accumulation builds up in our devices. From
the SDSE measurement and the observed current driven STT switching current of
0.8 mA in our spin valve devices, it was estimated that a temperature
difference of 230 K is needed to produce an equal amount of TSTT. Experiments
specifically focused on investigating TSTT show a response that is dominated by
overall heating of the magnetic layer. Comparing it to the current driven STT
experiments we estimate that only ~10% of the response is due to TSTT. This
leads us to conclude that switching dominated by TSTT requires a direct
coupling to a perfect heat sink to minimize the effect of overall heating.
Nevertheless the combined effect of heating, STT and TSTT could prove useful
for inducing magnetization switching when further investigated and optimized.
