Current-Induced Magnetization Reversal in High Magnetic Fields inCo/Cu/CoNanopillars

Current-induced magnetization dynamics in $\mathrm{C}\mathrm{o}/\mathrm{C}\mathrm{u}/\mathrm{C}\mathrm{o}$ trilayer nanopillars ($\sim 100\mathrm{n}\mathrm{m}$ in diameter) have been studied experimentally at low temperatures for large applied fields perpendicular to the layers. At 4.2 K an abrupt and hysteretic increase in resistance is observed at high current densities for one polarity of the current, comparable to the giant magnetoresistance effect observed at low fields. A micromagnetic model that includes a spin-transfer torque suggests that the current induces a complete reversal of the thin Co layer to alignment antiparallel to the applied field—that is, to a state of maximum magnetic energy.