Magnetic damping is a key metric for emerging technologies based on magnetic nanoparticles, such as spin torque memory and high-resolution biomagnetic imaging. Despite its importance, understanding of magnetic dissipation in nanoscale ferromagnets remains elusive, and the damping is often treated as a phenomenological constant. Here we report the discovery of a giant frequency-dependent nonlinear damping that strongly alters the response of a nanoscale ferromagnet to spin torque and microwave magnetic field. This novel damping mechanism originates from three-magnon scattering that is strongly enhanced by geometric confinement of magnons in the nanomagnet. We show that the giant nonlinear damping can invert the effect of spin torque on a nanomagnet leading to a surprising current-induced enhancement of damping by an antidamping torque. Our work advances understanding of magnetic dynamics in nanoscale ferromagnets and spin torque devices.
@article{arxiv.1803.10925,
title = {Giant resonant nonlinear damping in nanoscale ferromagnets},
author = {I. Barsukov and H. K. Lee and A. A. Jara and Y. -J. Chen and A. M. Gonçalves and C. Sha and J. A. Katine and R. E. Arias and B. A. Ivanov and I. N. Krivorotov},
journal= {arXiv preprint arXiv:1803.10925},
year = {2019}
}