Abstract
Excitation of magnetization dynamics by pure spin currents has been recently recognized as an enabling mechanism for spintronics and magnonics, which allows implementation of spin-torque devices based on low-damping insulating magnetic materials. Here we report the first spatially-resolved study of the dynamic modes excited by pure spin current in nanometer-thick microscopic insulating Yttrium Iron Garnet disks. We show that these modes exhibit nonlinear self-broadening preventing the formation of the self-localized magnetic bullet, which plays a crucial role in the stabilization of the single-mode magnetization oscillations in all-metallic systems. This peculiarity associated with the efficient nonlinear mode coupling in low-damping materials can be among the main factors governing the interaction of pure spin currents with the dynamic magnetization in high-quality magnetic insulators.
Highlights
IntroductionIt is long-known that the low damping in Yttrium Iron Garnet (YIG) facilitates the nonlinear coupling between dynamic magnetic modes[24]
The studied device consists of a Yttrium Iron Garnet (YIG)(20 nm)/Pt(8 nm) disk with a 2 μm diameter
The associated pure spin current is flowing in the out-ofplane direction and is injected into the YIG film[7] resulting in a spin-transfer torque (STT)[31,32] on its magnetization M
Summary
It is long-known that the low damping in YIG facilitates the nonlinear coupling between dynamic magnetic modes[24] This phenomenon was found to strongly affect the formation of spin-wave solitons[25] and result in a suppression of the nonlinear spatial self-localization phenomena[26,27], which play a crucial role in spin-torque driven nano-systems[20]. Just above the onset, the amplitude of the auto-oscillations rapidly saturates and the excited mode experiences a spatial broadening This phenomenon is opposite to the nonlinear self-localization observed in all-metallic systems and can be the main factor determining the response of the magnetization in low-damping materials to the spin current. We attribute these behaviors to the efficient nonlinear mode coupling, which prevents the growth of the amplitudes of the dynamic magnetization to the level necessary for the onset of nonlinear self-localization and formation of the bullet mode
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