Correlation between magnetism and lattice dynamics for cubic FeGe under pressure

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Physics

Background:

• Ferromagnetic (FM) cubic B20 FeGe exhibits complex behavior under pressure.
• Standard density functional theory (DFT) calculations often struggle to accurately predict its properties, particularly phonon anomalies.
• Understanding pressure-induced changes in magnetic and lattice dynamics is crucial for materials applications.

Purpose of the Study:

• To investigate the effects of applied pressure on the structural, electronic, lattice dynamical properties, and electron-phonon coupling in FM cubic B20 FeGe.
• To refine theoretical predictions using the spin-scaling exchange-correlation (ssxc) approach, aligning critical pressure with experimental values.
• To elucidate the correlation between magnetic moment and phonon linewidths under pressure.

Main Methods:

• Employed first-principles calculations.
• Utilized the spin-scaling exchange-correlation (ssxc) approach to adjust magnetic moment and phase energetics.
• Analyzed phonon dispersion, electron-phonon interaction, and electronic joint density of states.

Main Results:

• The ssxc approach successfully adjusted the critical pressure (pc) and brought the magnetic moment closer to experimental values.
• Phonon softening and large linewidths near the R-point were mitigated by ssxc and diminished significantly with increasing pressure.
• The pressure dependence of phonon anomalies and linewidths was found to parallel the magnetic moment's behavior, driven by electron-phonon matrix elements.

Conclusions:

• Applied pressure significantly influences the electronic and lattice dynamics of FeGe, reducing phonon anomalies.
• The ssxc method provides a more accurate theoretical framework for studying pressure effects in magnetic materials.
• The correlation between magnetic moment and phonon linewidths under pressure in FeGe is primarily governed by electron-phonon matrix elements, differing from other B20 materials.