Flexible Magnetoelastic Nanoscale-Thick FeGa/Pt Heterostructures for a Spintronic Terahertz Emitter

Spintronic terahertz (THz) emitters composed of nanoscale-thick ferromagnet/heavy metal multilayer structures exhibit an outstanding capability to generate high-quality, broadband THz pulses. However, there is a lack of research on laser-excited ultrafast spin current generation and manipulation in flexible nanoscale-thick magnetostrictive film/heavy metal heterostructures. Thus, we investigate photoinduced and strain-induced spin currents in flexible nanoscale-thick magnetostrictive film/heavy metal heterostructures employing THz emission spectroscopy. Under femtosecond laser excitation, ultrafast magnetization precession with a long lifetime is induced by photoinduced short strain waves in the magnetoelastic heterostructure due to magnetoelastic coupling. We observe a modulation in THz amplitudes with increasing external magnetic field strength, which aligns well with theoretical models based on magnetoelastic coupling in flexible magnetoelastic heterostructures. Specifically, we demonstrate how the strength of magnetoelastic coupling energy exchange affects ultrafast spin currents. Our work offers a significant method to advance the development of spintronic THz emitters based on nanoscale-thick magnetoelastic materials.