  We measure the temperature, magnetic-field, and current dependence for the
switching of nanomagnets by a spin-polarized current. Depending on current
bias, switching can occur between either two static magnetic states or a static
state and a current-driven precessional mode. In both cases, the switching is
thermally activated and governed by the sample temperature, not a higher
effective magnetic temperature. The activation barriers for switching between
static states depend linearly on current, with a weaker dependence for dynamic
to static switching.
