Large spin-wave bullet in a ferrimagnetic insulator driven by spin Hall effect

TL;DR

This paper demonstrates the direct imaging of nonlinear, self-localized spin-wave bullets in a ferrimagnetic insulator driven by spin Hall effect, revealing complex spin dynamics with potential for low-power spintronics.

Contribution

It provides the first direct spatial imaging of nonlinear spin-wave localization in a ferrimagnetic insulator driven by spin Hall effect, challenging the assumption of uniform precession.

Findings

Observation of a localized spin-wave 'bullet' in Y3Fe5O12.

Direct imaging of spin-torque ferromagnetic resonance in an insulator.

Evidence of nonlinear spin-wave phenomena in magnetic insulators.

Abstract

Due to its transverse nature, spin Hall effects (SHE) provide the possibility to excite and detect spin currents and magnetization dynamics even in magnetic insulators. Magnetic insulators are outstanding materials for the investigation of nonlinear phenomena and for novel low power spintronics applications because of their extremely low Gilbert damping. Here, we report on the direct imaging of electrically driven spin-torque ferromagnetic resonance (ST-FMR) in the ferrimagnetic insulator Y$_3$Fe$_5$O$_{12}$ based on the excitation and detection by SHEs. The driven spin dynamics in Y$_3$Fe$_5$O$_{12}$ is directly imaged by spatially-resolved microfocused Brillouin light scattering (BLS) spectroscopy. Previously, ST-FMR experiments assumed a uniform precession across the sample, which is not valid in our measurements. A strong spin-wave localization in the center of the sample is observed indicating the formation of a nonlinear, self-localized spin-wave `bullet'.