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Domain wall motion in perpendicular anisotropy nanowires with edge roughness
Maximilian Albert1, Matteo Franchin, Thomas Fischbacher
1School of Engineering Sciences, University of Southampton, Southampton, UK.
Journal of Physics. Condensed Matter : an Institute of Physics Journal
|December 17, 2011
Summary
Edge roughness in magnetic nanowires creates a depinning field, slowing domain wall motion initially but not affecting ultimate speed. Dynamic pinning occurs stochastically, influenced by roughness magnitude and correlation length.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Computational Physics
Background:
- Domain wall (DW) motion in magnetic nanowires is crucial for spintronic devices.
- Perpendicular magnetic anisotropy (PMA) is essential for high-density magnetic storage.
- Understanding DW dynamics under realistic conditions, including defects, is vital for device performance.
Purpose of the Study:
- To investigate the impact of edge roughness on field-driven domain wall motion in nanowires with PMA.
- To quantify the effects of roughness magnitude and correlation length on DW depinning and velocity.
- To analyze the phenomenon of dynamic pinning in the presence of edge imperfections.
Main Methods:
- Finite element micromagnetic simulations were employed.
- Edge roughness was introduced by deforming the finite element mesh.
- Correlation length and magnitude of roughness were systematically varied.
Main Results:
- Walker breakdown was observed, with steady motion below H(c) and oscillatory motion above.
- Edge roughness introduced a depinning field and significantly reduced transient DW velocity.
- Asymptotic DW velocity and the critical Walker field H(c) were largely unaffected by roughness.
- Dynamic pinning was observed as a stochastic process, dependent on field strength and DW oscillation cycle.
- Depinning field scaled linearly with roughness magnitude, with peak pinning at correlation lengths matching DW width.
Conclusions:
- Edge roughness in magnetic nanowires introduces significant depinning effects and dynamic pinning.
- While transient DW motion is slowed, steady-state velocity and Walker breakdown fields remain robust against roughness.
- The interplay between roughness characteristics and DW width dictates pinning strength, offering insights for defect engineering in spintronic devices.
