Spin-torque-driven ballistic precessional switching with 50 ps impulses

We demonstrate reliable spin-torque-driven ballistic precessional switching using 50 ps current impulses in a spin-valve device that includes both in-plane and out-of-plane spin polarizers. Different threshold currents as the function of switching direction and current polarity enable the final orientation of the magnetic free layer to be steered, in accord with a macrospin analysis, by the sign of the pulse, eliminating the need for read-before-write toggle operation. The pulse amplitude windows for this deterministic operation are wider and more symmetric as a function of current polarity for shorter impulses, while inhomogeneous fringe fields from the polarizers lead to asymmetries as a function of current direction.