We present a comprehensive experimental and numerical study of magnetization dynamics triggered in a thin metallic film by single-cycle terahertz pulses of ∼20 MV/m electric field amplitude and ∼1 ps duration. The experimental dynamics is probed using the femtosecond magneto-optical Kerr effect (MOKE), and it is reproduced numerically using macrospin simulations. The magnetization dynamics can be decomposed in three distinct processes: a coherent precession of the magnetization around the terahertz magnetic field, an ultrafast demagnetization that suddenly changes the anisotropy of the film, and a uniform precession around the equilibrium effective field that is relaxed on the nanosecond time scale, consistent with a Gilbert damping process. Macrospin simulations quantitatively reproduce the observed dynamics, and allow us to predict that novel nonlinear magnetization dynamics regimes can be attained with existing table-top terahertz sources.
@article{arxiv.1903.08395,
title = {Nonlinear magnetization dynamics driven by strong terahertz fields},
author = {Matthias Hudl and Massimiliano d'Aquino and Matteo Pancaldi and See-Hun Yang and Mahesh G. Samant and Stuart S. P. Parkin and Hermann A. Dürr and Claudio Serpico and Matthias C. Hoffmann and Stefano Bonetti},
journal= {arXiv preprint arXiv:1903.08395},
year = {2019}
}