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

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.