Using thin film pillars ~100 nm in diameter, containing two ferromagnetic Co layers of different thicknesses separated by a paramagnetic Cu spacer, we examine effects of torques due to spin-polarized currents flowing perpendicular to the layers. In accordance with spin-transfer theory, spin-polarized electrons flowing from the thin to the thick Co layer can switch the magnetic moments of the layers antiparallel, while a reversed electron flow causes switching to a parallel state. When large magnetic fields are applied, the current no longer fully reverses the magnetic moment, but instead stimulates spin-wave excitations.
@article{arxiv.cond-mat/9908231,
title = {Current-driven Magnetization Reversal and Spin Wave Excitations in Co/Cu/Co Pillars},
author = {J. A. Katine and F. J. Albert and R. A. Buhrman and E. B. Myers and D. C. Ralph},
journal= {arXiv preprint arXiv:cond-mat/9908231},
year = {2009}
}