Narrow autoresonant magnetization structures in finite-length ferromagnetic nanoparticles

Area of Science:

• Condensed Matter Physics
• Materials Science
• Magnetism

Background:

• Controlling magnetization dynamics in ferromagnetic nanoparticles is crucial for applications like data storage and spintronics.
• Exciting and localizing large-amplitude magnetization structures presents significant challenges due to dissipation and field requirements.

Purpose of the Study:

• To propose and analyze an autoresonant excitation method for large-amplitude uniformly precessing magnetization structures.
• To investigate the role of boundary conditions in localizing these structures within finite-length ferromagnetic nanoparticles.
• To examine the influence of dissipation on the excitation threshold and the properties of the excited structures.

Main Methods:

• Utilized the Landau-Lifshitz-Gilbert model to simulate magnetization dynamics.
• Employed a spatially uniform, oscillating, chirped frequency magnetic field for excitation.
• Imposed localization via boundary conditions and analyzed the system's response to driving field amplitude and dissipation.

Main Results:

• The autoresonant approach successfully excites large-amplitude magnetization structures, requiring the driving field amplitude to exceed a specific threshold.
• Autoresonant driving effectively compensates for dissipation, though it reduces the maximum achievable amplitude of the excited structures.
• Simulations revealed fully nonlinear localized autoresonant solutions behaving analogously to quasiparticles, with precession frequency locked to the drive.

Conclusions:

• The proposed autoresonant method offers effective control over magnetization dynamics in ferromagnetic nanoparticles.
• The excited magnetization profiles approach the soliton limit under specific conditions of nanoparticle length and excitation amplitude.
• This approach provides a pathway for manipulating magnetic structures with potential applications in advanced magnetic devices.