  We investigate the angular dependence of the spin torque generated when
applying a temperature difference across a spin-valve. Our study shows the
presence of a non-trivial fixed point in this angular dependence, i.e. the
possibility for a temperature gradient to stabilize radio frequency
oscillations without the need for an external magnetic field. This so called
"wavy" behavior can already be found upon applying a voltage difference across
a spin-valve but we find that this effect is much more pronounced with a
temperature difference. Our semi-classical theory is parametrized with
experimentally measured parameters and allows one to predict the amplitude of
the torque with good precision. Although thermal spin torque is by nature less
effective than its voltage counterpart, we find that in certain geometries,
temperature differences as low as a few degrees should be sufficient to trigger
the switching of the magnetization.
