2(b) and 2(c), a dc current I d c = − 42 mA applied in the NM layer in the direction opposite to that in Fig. Figure 2(a) shows the FMR spectrum of the YIG (154 nm)/ bilayer, measured at 3.0 GHz, with no current applied in the NM layer, as well as the fitting curve that gives a linewidth Δ H = 4.52 Oe. The effect of the spin-transfer-torque on the magnetization dynamics produced by the spin current is demonstrated in the various panels of Fig. 23 However, only with the development of techniques for the fabrication of high-quality nanometer-thick YIG films 24–29 did insulator-based magnonic nano-oscillators became feasible. 17–22 The research in the field gained additional impetus with the observation of spin wave driving by spin currents in the insulating ferrimagnet yttrium iron garnet (YIG), known for its very small magnetic damping. 6–16 Later, it was demonstrated that magnetic nano-oscillators can be driven by pure spin currents, generated by the conversion of charge currents in metallic films through the spin Hall effect. 2–5 By suitably injecting spin-polarized currents into metallic magnetic multilayers, several groups demonstrated the magnetization precession at microwave frequencies, making possible the implementation of tunable spin-transfer-torque nano-oscillators. 1 Some spin current effects that have attracted attention are based on the antidamping spin torque exerted on the magnetization of a ferromagnetic film. Spin currents are at the root of spintronic devices aiming to improve information and communication technologies. We interpret the BLS signal as due to phonons excited by the magnonic spin current injected into the YIG film, in a process that is the Onsager reciprocal of the spin pumping by coherent elastic waves. The second, observed by Brillouin light scattering (BLS), is the excitation of quasi-particles in the YIG film with frequencies that do not vary with the applied magnetic field. The first, demonstrated by ferromagnetic resonance (FMR) experiments, is the dramatic reduction of the magnon damping measured by the FMR linewidth due to the spin torque produced by the spin current. Here, we show experimentally two effects of the large spin current generated by the giant spin Hall effect in a platinum strip with nanoscopic silver particles adjacent to a film of the insulating ferrimagnet yttrium iron garnet (YIG). In recent years, several groups reported experiments in which spin currents are used to excite coherent magnetization dynamics in magnetic nanostructures. Spin current phenomena are at the heart of the active research field of spintronics that aims to develop new perspectives for emerging information technologies.
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