Hysteresis multicycles in nanomagnet arrays

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Physics

Background:

• Understanding magnetic hysteresis in nanomaterials is crucial for data storage and spintronic devices.
• Existing scalar models of hysteresis, like Ising models, offer simplified frameworks but may not capture complex dynamics.

Purpose of the Study:

• To predict and analyze physical effects in single-domain nanomagnet arrays using realistic simulations.
• To investigate the occurrence and influencing factors of hysteretic multicycles.
• To differentiate between vector Landau-Lifshitz-Gilbert (LLG) dynamics and scalar hysteresis models.

Main Methods:

• Performing simulations with a realistic model Hamiltonian and physical parameters.
• Utilizing continuous spin dynamics via the Landau-Lifshitz-Gilbert (LLG) equation.
• Analyzing the impact of system size, anisotropy, disorder, and frustration on magnetic behavior.

Main Results:

• Predicted hysteretic multicycles in nanomagnets, with probabilities up to 0.6 in certain parameter spaces.
• Identified that larger, more anisotropic nanomagnets, along with disorder and frustration, promote multicycle behavior.
• Demonstrated a fundamental difference between vector LLG dynamics and scalar hysteresis models, specifically regarding spin and external field inversion symmetry.

Conclusions:

• Hysteretic multicycles are a predictable phenomenon in nanomagnets, significantly influenced by material properties and system configuration.
• The vector LLG equation reveals dynamics that break inversion symmetry, unlike simpler scalar models, which has critical experimental consequences for understanding nanomagnet behavior.