Theory of Defect-Induced Crystal Field Perturbations in Rare-Earth Magnets

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Materials Science

Background:

• Single-ion anisotropy is crucial for rare-earth (RE) magnet performance.
• Point defects can significantly alter magnetic properties.
• Understanding defect-induced anisotropy is essential for designing advanced magnetic materials.

Purpose of the Study:

• To develop a theoretical framework for single-ion anisotropy in RE magnets with point defects.
• To investigate the impact of Ti substitutions on the crystal field in SmFe12 magnets.
• To provide a computationally efficient method for simulating defect effects on anisotropy.

Main Methods:

• First-principles calculations were employed to study the RE-lean 1∶12 magnet class.
• A screened point charge model was used to describe crystal field perturbations efficiently.
• Analytical expressions for anisotropy energy were derived for atomistic spin dynamics simulations.

Main Results:

• Ti substitutions in SmFe12 were shown to perturb the crystal field, creating new coefficients due to reduced symmetry.
• The screened point charge model accurately and efficiently describes these perturbations.
• Compositional disorder, even in structurally single-phase samples, leads to a varied anisotropy profile at the atomistic level.

Conclusions:

• The developed theory and model provide an efficient way to incorporate point defect effects into magnetic simulations.
• Significant crystal field perturbations highlight the impact of compositional disorder on magnetic anisotropy.
• These findings are crucial for understanding and controlling localized magnetic objects like domain walls and skyrmions in RE magnets.