Subnanosecond magnetization reversal in magnetic nanopillars by spin angular momentum transfer

Sub-ns magnetization switching has been triggered by spin momentum transfer in pulsed current in pillar shaped $\mathrm{CoFe}∕\mathrm{Cu}∕\mathrm{CoFe}$ trilayers. By analyzing the change in magneto-resistance induced after the application of individual short current pulses $\left(100\mathrm{ps}–10\mathrm{ns}\right)$ , we measured the probability of magnetization reversal as a function of the current pulse magnitude, polarity and duration, at various temperatures between 150 and $300\mathrm{K}$ . At all studied temperatures, the reversal process can take place within a few $100\mathrm{ps}$ . The energy cost of the reversal scales favorably with the switching speed and decreases in the $1\mathrm{pJ}$ range when using $100\mathrm{ps}$ current pulses at $300\mathrm{K}$ . Significantly higher switching speeds are obtained at lower temperatures, which is opposite to a thermal activation of the reversal.