A long-ranged dynamic interaction between ferromagnetic films separated by normal-metal spacers is reported, which is communicated by nonequilibrium spin currents. It is measured by ferromagnetic resonance (FMR) and explained by an adiabatic spin-pump theory. In FMR the spin-pump mechanism of spatially separated magnetic moments leads to an appreciable increase in the FMR line width when the resonance fields are well apart, and results in a dramatic line-width narrowing when the FMR fields approach each other.
@article{arxiv.cond-mat/0210588,
title = {Dynamic exchange coupling in magnetic bilayers},
author = {Bret Heinrich and Yaroslav Tserkovnyak and Georg Woltersdorf and Arne Brataas and Radovan Urban and Gerrit E. W. Bauer},
journal= {arXiv preprint arXiv:cond-mat/0210588},
year = {2009}
}