In recent years, Spin Orbit interaction as a source of spin current has been widely used through the physics of Spin Hall Effect (SHE). The peculiar symmetry of SHE allows creating a spin accumulation at the interface between a spin-orbit metal and a magnetic insulator that could lead to a net pure spin current flowing from the metal into the insulator. This spin current will induce a torque on the magnetization and eventually could drive it into steady motion. As a ferromagnetic insulator with a very low Gilbert damping, Yttrium Iron Garnet (YIG) is a very promising candidate to investigate pure spin current phenomena. Only very recently, with the developments in preparation of high-quality nanometer-thick YIG films, the implementation of insulator-based spin-torque devices became practically feasible.
Here, we report on the excitation of auto-oscillations in microstructures of YIG(20nm)\Pt(8nm) driven by Spin Orbit torque (SOT). By injection of a dc current in the adjacent Pt layer, we have been able to prove that the SOT due to SHE is sufficiently strong and efficient to drive the YIG magnetization dynamics at frequencies that closely follow the ferromagnetic resonance mode. These auto-oscillations have been detected either inductively using a spectrum analyzer or directly observed using micro-focus Brillouin Light Scattering. Furthermore, we achieved an efficient control of spin waves attenuation length in a YIG waveguide using the SHE in the sub-critical regime i.e. below the auto-oscillations threshold. We believe that our finding pave the path to active magnonics devices made out of YIG films.
Martin Collet, Paolo Bortolotti, Vincent Cros, Abdelmadjid Anane, José Luis Prieto, Manuel Muñoz, Jamal Ben Youssef, Vladimir Naletov, Grégoire de Loubens, Olivier Klein, Michael Evelt, Vladimir Bessonov, Sergej O. Demokritov, and Vladislav E. Demidov, "Auto-oscillation and spin-wave propagation in ultra-thin YIG microstructures (Conference Presentation)," Proc. SPIE 10357, Spintronics X, 1035714 (Presented at SPIE Nanoscience + Engineering: August 08, 2017; Published: 21 September 2017); https://doi.org/10.1117/12.2272149.5583428444001.
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