Anisotropic and Controllable Nonlocal Damping in Exchange Bias Bilayers

Area of Science:

• Spintronics
• Condensed Matter Physics
• Materials Science

Background:

• Antiferromagnetic (AFM)/ferromagnetic (FM) interfaces are crucial for spintronics applications.
• Exchange bias (EB) and spin current phenomena at these interfaces are of significant interest.
• The precise relationship between EB and spin current remains an active area of research.

Purpose of the Study:

• To investigate the relationship between exchange bias and nonlocal damping in Co/CoO bilayers.
• To explore the influence of controllable magnetic anisotropy on spin current properties.
• To understand the impact of the training effect on damping in EB systems.

Main Methods:

• Fabrication of Co/CoO bilayers using oblique deposition of Co and in situ oxidation of CoO.
• Characterization of magnetic properties, including uniaxial magnetic anisotropy (UMA).
• Measurement of nonlocal damping and its dependence on UMA and training effects.

Main Results:

• Observation of anisotropic and controllable nonlocal damping in the Co/CoO system.
• Demonstration that the Gilbert damping constant is higher along the hard axis compared to the easy axis of UMA.
• Evidence that the training effect enhances nonlocal damping due to reorientation of interfacial uncompensated AFM spins.

Conclusions:

• The study provides valuable insights into how exchange bias influences nonlocal damping.
• The findings suggest a new method for controlling spin current in antiferromagnetic spintronic devices.
• Controllable anisotropy and training effects are key factors in manipulating spin dynamics at AFM/FM interfaces.