Precharging strategy to accelerate spin-transfer switching below the nanosecond

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Abstract
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 2ns down to at least 200ps. 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 2ns, hence the precharging strategy loses its efficiency for longer pulses, in agreement with experiments.