The torque generated by the transfer of spin angular momentum from a spin-polarized current to a nanoscale ferromagnet can switch the orientation of the nanomagnet much more efficiently than a current-generated magnetic field, and is therefore in development for use in next-generation magnetic random access memory (MRAM). Up to now, only DC currents and square-wave current pulses have been investigated in spin-torque switching experiments. Here we present measurements showing that spin transfer from a microwave-frequency pulse can produce a resonant excitation of a nanomagnet and lead to improved switching characteristics in combination with a square current pulse. With the assistance of a microwave-frequency pulse, the switching time is reduced and achieves a narrower distribution than when driven by a square current pulse alone, and this can permit significant reductions in the integrated power required for switching. Resonantly excited switching may also enable alternative, more compact MRAM circuit architectures.
@article{arxiv.0803.2880,
title = {Resonant Spin-Transfer-Driven Switching of Magnetic Devices Assisted by Microwave Current Pulses},
author = {Y. -T. Cui and J. C. Sankey and C. Wang and K. V. Thadani and Z. -P. Li and R. A. Buhrman and D. C. Ralph},
journal= {arXiv preprint arXiv:0803.2880},
year = {2009}
}