Interatomic exchange interactions for finite-temperature magnetism and nonequilibrium spin dynamics

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Understanding magnetic exchange interactions is crucial for designing advanced magnetic materials.
• Existing models often simplify magnetic configurations, limiting their applicability to complex systems.
• Ab initio calculations provide a fundamental approach to deriving material properties.

Purpose of the Study:

• To derive ab initio exchange parameters for general noncollinear magnetic configurations.
• To investigate the presence and significance of anisotropic-like terms in magnetic exchange interactions.
• To develop a more accurate theoretical framework for finite-temperature magnetic properties.

Main Methods:

• Utilizing a multiple scattering formalism for ab initio calculations.
• Deriving general exchange formulas applicable to various magnetic configurations.
• Calculating magnon spectra for bcc Fe using configuration-dependent exchange parameters.

Main Results:

• An anisotropic-like term in the exchange formula was identified, present even without spin-orbit coupling.
• This term significantly impacts collinear configurations in materials like bcc Fe.
• The derived parameters accurately reproduce experimental results for bcc Fe magnon spectra at finite temperatures.

Conclusions:

• The derived ab initio exchange parameters offer a more comprehensive description of magnetic interactions.
• The identified anisotropic term is essential for accurate modeling of magnetic behavior, particularly at finite temperatures.
• This work provides a robust theoretical foundation for studying complex magnetic phenomena in materials.