Abstract-Nonlinear magnetization dynamics driven by strong terahertz fields

Matthias Hudl, Massimiliano d'Aquino, Matteo Pancaldi, See-Hun Yang, Mahesh G. Samant, Stuart S. P. Parkin, Hermann A. Dürr, Claudio Serpico, Matthias C. Hoffmann, Stefano Bonetti

https://arxiv.org/abs/1903.08395

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 ∼1ps 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.