Coherent Magnetization Dynamics in Ni80Fe20 Thin Films Incorporated in Fe/Au Spintronic Terahertz Emitters

摘要

Coherent magnetization dynamics at terahertz (THz) frequencies is achieved by directly incorporating ferromagnetic Ni ₈₀ Fe ₂₀ thin films into Fe/Au bilayer spintronic THz emitters. Electrooptical (EO) sampling demonstrates a generation of THz pulses centered near ~2.8 THz with a bandwidth in the 1–4 THz range. Ni ₈₀ Fe ₂₀ magnetization is directly coupled to the magnetic component of the THz wave, in which the large-amplitude magnetization precession is found phase locked with the THz pulse. The THz-induced magnetization dynamics can be controlled by external bias magnetic fields. The micromagnetic and analytical models based on the Landau–Lifshitz–Gilbert (LLG) equation are in good agreement with experimental findings and verify that the underlying mechanism of the THz-induced magnetization dynamics is the Zeeman coupling between the magnetic component of the THz field and Ni ₈₀ Fe ₂₀ magnetization. Our results open the opportunities for the use of low-cost metallic spintronic THz emitters in the studies of THz-induced magnetization dynamics in magnetic thin films.