Anisotropic Absorption of Pure Spin Currents

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Spin transfer in magnetic multilayers is crucial for ultrafast, low-power electronic devices.
• Spin pumping is a key phenomenon in spintronic devices, involving the transfer of spin angular momentum.

Purpose of the Study:

• To investigate spin pumping in spin valves.
• To demonstrate the induction of spin pumping anisotropy via angular dependence of Gilbert damping.
• To explore mechanisms for enhanced spin torques and angular control in spintronic devices.

Main Methods:

• Utilized lab- and synchrotron-based ferromagnetic resonance (FMR).
• Studied spin valves with crystalline Co_{50}Fe_{50} as the source layer and polycrystalline Ni_{81}Fe_{19} as the spin sink layer.
• Investigated the role of the spin diffusion length in Chromium (Cr).

Main Results:

• Demonstrated that in-plane damping variations in the source layer induce anisotropic Gilbert damping (α) in the spin sink layer.
• Determined the spin diffusion length in Cr to be 8 nm.
• Showed that the observed anisotropy is suppressed above the spin diffusion length and is independent of static exchange coupling.

Conclusions:

• Anisotropy in spin pumping can be effectively controlled by the angular dependence of Gilbert damping in the spin sink layer.
• These findings provide insights into spin current transmission and absorption.
• The study offers a pathway for realizing enhanced spin torques and angular control in next-generation spintronic devices.