A nonlinear model of spin wave excitation using a point contact in a thin ferromagnetic film is introduced. Large-amplitude magnetic solitary waves are computed, which help explain recent spin-torque experiments. Numerical simulations of the fully nonlinear model predict excitation frequencies in excess of 0.2 THz for contact diameters smaller than 6 nm. Simulations also predict a saturation and red shift of the frequency at currents large enough to invert the magnetization under the point contact. The theory is approximated by a cubic complex Ginzburg-Landau type equation. The mode's nonlinear frequency shift is found by use of perturbation techniques, whose results agree with those of direct numerical simulations.
@article{arxiv.cond-mat/0509265,
title = {Theory of Magnetodynamics Induced by Spin Torque in Perpendicularly Magnetized Thin Films},
author = {M. A. Hoefer and M. J. Ablowitz and B. Ilan and M. R. Pufall and T. J. Silva},
journal= {arXiv preprint arXiv:cond-mat/0509265},
year = {2009}
}