Terahertz excitation of spin dynamics in ferromagnetic thin films incorporated in metallic spintronic-THz-emitter

Abstract

An experimental approach to trigger ultrafast spin dynamics at frequencies of the terahertz (THz) regime is explored by directly incorporating ferromagnetic Ni80Fe20 films to a Fe/Au spintronic-THz-emitter. It is found that Ni80Fe20 magnetization is directly coupled to the terahertz magnetic fields, in which the magnetic responses of Ni80Fe20 are phase-locked with terahertz pulses. High efficiency of metallic spintronic-terahertz emitters in driving terahertz-induced magnetization dynamics is observed; the maximum precession amplitude of the out-of-plane component of the Ni80Fe20 magnetization reaches over 10% of its saturation magnetization. Analytical integrations of THz magnetic field pulses reproduce the experimental results, confirming that the underlying mechanism of the observed spin dynamics is the Zeeman coupling between the terahertz magnetic field and magnetization in the Ni80Fe20 film. Our results open up possibilities for the studies of terahertz spin dynamics by integrating highly efficient low-cost metallic spintronic-THz-emitters into magnetic thin film elements.