Studies of current-driven excitations in Co/Cu/Co trilayer nanopillars

We measure the dynamic resistance of a Co/Cu/Co trilayer nanopillar at varied magnetic field H and current I. The resistance displays the usual behavior, almost symmetric in H, both when magnetization switching is hysteretic at small I, H, and reversible at larger I, H. We show differences in the I, H magnetization stability diagram measured by holding I fixed and varying H and vice versa. We also show how the peak in dV/dI associated with telegraph noise in the reversible switching regime, is calculated from the telegraph noise variations with I. Lastly, we show data for a similar sample that displays behavior asymmetric in H, and a negative reversible switching peak instead of a usual positive one.