Magnons from time-dependent density-functional perturbation theory and nonempirical Hubbard functionals.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Chemistry

Background:

• Spin excitations are crucial for magnetic properties and magnonic devices.
• Accurate modeling of spin excitations in transition-metal and rare-earth compounds is challenging.
• Existing methods often rely on empirical parameters or simplified models.

Purpose of the Study:

• To present a fully first-principles approach for calculating spin-wave spectra.
• To enable accurate modeling of magnons in both collinear and noncollinear magnetic systems.
• To overcome limitations of empirical Hubbard U parameters and Heisenberg Hamiltonians.

Main Methods:

• Utilizing time-dependent density-functional perturbation theory (TDDFPT) with nonempirical Hubbard functionals.
• Implementing a general noncollinear formulation for broad applicability.
• Employing the Liouville-Lanczos approach to efficiently evaluate dynamical spin susceptibility.

Main Results:

• The novel method accurately calculates spin-wave spectra.
• Demonstrated remarkable agreement with experimental data for NiO and MnO.
• Satisfies the Goldstone condition without empirical rescaling or sum rule enforcement.

Conclusions:

• The developed computational scheme provides a robust tool for studying spin excitations.
• Highlights the importance of nonempirical Hubbard corrections for accurate predictions.
• Shows great promise for describing collective spin excitations in complex materials with localized electronic states.