Precharging strategy to accelerate spin-transfer switching below the nanosecond

We compared different ways of inducing magnetization switching by spin momentum transfer in pillar shaped CoFe/Cu/CoFe trilayers using sub-ns-current pulses. In comparison with switching induced by a single sub-ns pulse, precharging the device with a bias current prior to the application of the pulse proved to lower the required peak current. Precharging is efficient for pulses ranging from 2 ns down to at least 200 ps. Simulations indicate that the bias current prepares the magnetization in a precession state that provides an enhanced susceptibility to the spin torque of the pulsed current. The precession settling time is typically 2 ns, hence the precharging strategy loses its efficiency for longer pulses, in agreement with experiments. 0 2005 American Institute of Physics.