A three-dimensional spin-diffusion model for micromagnetics

Area of Science:

• * Computational physics and materials science.
• * Spintronics and condensed matter physics.

Background:

• * Existing models for spin-torque phenomena, such as Slonzewski's multi-layer model and Zhang and Li's domain-wall motion model, have limitations in fully describing complex spin dynamics.
• * Understanding spin accumulation and nonlocal effects is crucial for advancing spintronic devices.

Purpose of the Study:

• * To develop and validate a unified numerical model for time-dependent spin-diffusion coupled with the Landau-Lifshitz-Gilbert equation.
• * To demonstrate the capability of this model to incorporate and reproduce the physics described by established spin-torque models.
• * To investigate the time-dependent behavior of spin accumulation.

Main Methods:

• * Numerical solution of a time-dependent three-dimensional spin-diffusion model.
• * Coupling the spin-diffusion model with the Landau-Lifshitz-Gilbert equation.
• * Validation against the Slonzewski and Zhang and Li spin-torque models.

Main Results:

• * The developed spin-diffusion model successfully incorporates the nonlocal effects described by the Slonzewski model.
• * The model captures spin accumulation resulting from magnetization gradients, as detailed in the Zhang and Li model.
• * The time-dependent evolution of spin accumulation is accurately resolved.

Conclusions:

• * The unified spin-diffusion model provides a comprehensive framework for simulating spin-torque phenomena.
• * This approach offers a more complete description of spin dynamics, including nonlocal effects and time-dependent spin accumulation.
• * The validated model can be used to explore and design advanced spintronic devices.