  We provide new data on current-driven switching in Permalloy (Py = Ni84Fe16)
based nanopillars at room temperature and 4.2K that confirm and extend
previously published work. We present data for both uncoupled and
antiferromagnetically coupled samples. The latter confirm prior results for
Co/Cu/Co. We show that inserting sufficiently strong spin-flip-scattering into
the Cu layer eliminates hysteretic current-driven switching. This result may
have ramifications for understanding current-driven switching.
