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.