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Direct observation of dynamic modes excited in a magnetic insulator by pure spin current

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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.

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Spatial characteristics of the field-driven ferromagnetic resonance mode.(a,b) Spatial maps of the FMR mode measured by BLS at I = 0 and 7 mA, respectively. The contours of the disk and the edges of the electrodes are shown by white lines. The maps were recorded at H0 = 1000 Oe. (c,d) Normalized spatial maps of the intensity of the dynamic magnetization in the FMR mode obtained from micromagnetic simulations. (c) corresponds to I = 0 and (d) corresponds to I = 7 mA.
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f5: Spatial characteristics of the field-driven ferromagnetic resonance mode.(a,b) Spatial maps of the FMR mode measured by BLS at I = 0 and 7 mA, respectively. The contours of the disk and the edges of the electrodes are shown by white lines. The maps were recorded at H0 = 1000 Oe. (c,d) Normalized spatial maps of the intensity of the dynamic magnetization in the FMR mode obtained from micromagnetic simulations. (c) corresponds to I = 0 and (d) corresponds to I = 7 mA.

Mentions: Finally, we address the nature of the localized dynamic mode, which is excited in the YIG disk at I = IC before the nonlinear broadening takes place. To understand why this mode shows a strong localization at the center of the disk, we perform ferromagnetic-resonance (FMR) measurements based on the excitation of the system by a dynamic magnetic field created by an additional 5 μm wide stripe antenna aligned parallel to the gap between the electrodes (see also Supplementary Figure S1). In Fig. 5a,b we show the spatial maps of the field-driven FMR mode recorded by BLS without any dc current in Pt and at I = 7 mA < IC, respectively. The maps clearly demonstrate that the FMR mode initially spread over the entire disk becomes localized at its center when the dc current is applied. We emphasize that the measurements were performed at sufficiently small microwave powers to exclude any nonlinear self-localization effects39. Therefore, the observed localization can only be attributed to the joint effect of the Oersted field of the dc current, the local reduction of the magnetization due to the Joule heating, and the partial compensation of the dynamic damping by the pure spin current injected into the YIG film.


Direct observation of dynamic modes excited in a magnetic insulator by pure spin current
Spatial characteristics of the field-driven ferromagnetic resonance mode.(a,b) Spatial maps of the FMR mode measured by BLS at I = 0 and 7 mA, respectively. The contours of the disk and the edges of the electrodes are shown by white lines. The maps were recorded at H0 = 1000 Oe. (c,d) Normalized spatial maps of the intensity of the dynamic magnetization in the FMR mode obtained from micromagnetic simulations. (c) corresponds to I = 0 and (d) corresponds to I = 7 mA.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016739&req=5

f5: Spatial characteristics of the field-driven ferromagnetic resonance mode.(a,b) Spatial maps of the FMR mode measured by BLS at I = 0 and 7 mA, respectively. The contours of the disk and the edges of the electrodes are shown by white lines. The maps were recorded at H0 = 1000 Oe. (c,d) Normalized spatial maps of the intensity of the dynamic magnetization in the FMR mode obtained from micromagnetic simulations. (c) corresponds to I = 0 and (d) corresponds to I = 7 mA.
Mentions: Finally, we address the nature of the localized dynamic mode, which is excited in the YIG disk at I = IC before the nonlinear broadening takes place. To understand why this mode shows a strong localization at the center of the disk, we perform ferromagnetic-resonance (FMR) measurements based on the excitation of the system by a dynamic magnetic field created by an additional 5 μm wide stripe antenna aligned parallel to the gap between the electrodes (see also Supplementary Figure S1). In Fig. 5a,b we show the spatial maps of the field-driven FMR mode recorded by BLS without any dc current in Pt and at I = 7 mA < IC, respectively. The maps clearly demonstrate that the FMR mode initially spread over the entire disk becomes localized at its center when the dc current is applied. We emphasize that the measurements were performed at sufficiently small microwave powers to exclude any nonlinear self-localization effects39. Therefore, the observed localization can only be attributed to the joint effect of the Oersted field of the dc current, the local reduction of the magnetization due to the Joule heating, and the partial compensation of the dynamic damping by the pure spin current injected into the YIG film.

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Related in: MedlinePlus