Ab Initio Study of the β-Fe₂O₃ Phase.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Materials Science

Background:

• The cubic bulk β-phase of iron(III) oxide (Fe2O3) presents a complex magnetic structure due to competing magnetic couplings.
• Identifying the magnetic ground state of β-Fe2O3 is challenging due to potential magnetic frustration in its high-symmetry crystal structure.

Purpose of the Study:

• To investigate the electronic and magnetic properties of the cubic bulk β-phase of Fe2O3 using first-principles calculations.
• To determine the definitive magnetic ground state of β-Fe2O3 and compare it with other phases (α and γ).

Main Methods:

• First-principles calculations were employed to analyze the electronic and magnetic properties.
• Various possible magnetic phases, including ferrimagnets, altermagnets, and Kramers antiferromagnets, were examined.
• Density of states and band gap evolution were studied as a function of electronic correlations (Coulomb repulsion).

Main Results:

• The magnetic ground state of bulk β-Fe2O3 was identified as a Kramers antiferromagnet.
• A bulk d-wave altermagnetic phase was found to be energetically close to the ground state.
• For appropriate Coulomb repulsion, β-Fe2O3 behaves as a charge-transfer insulator with an indirect band gap of 1.5 eV.

Conclusions:

• The study definitively establishes the Kramers antiferromagnetic ground state for β-Fe2O3, contrasting with the altermagnetic α-phase and ferrimagnetic γ-phase.
• The calculated Néel temperature is lower than other phases due to the cancellation of first-neighbor interactions.
• These findings provide a foundation for ab initio studies of β-Fe2O3 nanoparticles and alloys.