Study of the Electronic Structure and Magnetic Properties of ε-Fe₂O₃by First-Principles Calculation and Molecular Orbital Calculations

Abstract

ε-Fe 2 O 3 is known to exhibit a large coercive field of 20 kOe at room temperature. In this work, we examine the electronic structure and magnetic properties of ε-Fe 2 O 3 using first-principles calculation and discrete variational (DV)-Xα molecular orbital calculation. The first-principles calculation shows that ε-Fe 2 O 3 is a charge-transfer type insulator with a valence band of O2p and a conduction band of Fe3d. The optical transition is an indirect transition from Γ to S point. The density of states (DOS) of the four nonequivalent Fe sites (Fe A , Fe B , Fe C , and Fe D ) indicates that ε-Fe 2 O 3 has ferrimagnetic ordering due to α spins on Fe B and Fe C and β spins on Fe A and Fe D . The charge density map of the occupied Fe3d band displays a strong hybridization between Fe3d and O2p. Molecular orbital calculation for each Fe site also supports the existence of a strong Fe3d−O2p hybridization. Such a strong hybridization induces nonzero orbital angular momentum L on Fe3d through the partial charge transfer from O2p to Fe3d. The appearance of L causes a large magnetic anisotropy through spin−orbit interaction, which induces the large coercive field.

Unusual Temperature Dependence of Zero-Field Ferromagnetic Resonance in Millimeter Wave Region on Al-Substituted ε-Fe2O3

“…This result was consistent with the experimental results from neutron diffraction measurements, Mössbauer spectroscopy measurements, etc. [13,14], and was also consistent with first-principles calculation results [33]. …”

Epitaxially stabilized thin films of ε-Fe2O3 (001) grown on YSZ (100)

“…This large magnetocrystalline anisotropy, induced by the lattice distortions of the Fe 3+ coordination polyhedra, leads to a strong hybridization between the Fe 3d and the O 2p orbitals, resulting in a non-zero orbital magnetic moment L , which, through spin-orbit coupling, defines a magnetic-easy axis. Later, first principle calculations supported the experimental finding, predicting that the magnetic easy axis lies along the crystal a axis direction 24 .…”

Tailoring of Optoelectronic Properties of ϵ‐Fe2O3 Thin Films Through Insertion of Organic Interlayers

“…Finally we estimated the optical bandgaps ( E g ) for our SL thin films based on the data in Figure . To the best of our knowledge no experimental bandgap values have been reported for ϵ‐Fe 2 O 3 but a theoretical study finds the indirect bandgap of ϵ‐Fe 2 O 3 at 1.6 eV . Thus assuming an indirect bandgap, we determined the E g values by extrapolating the linear regions of the ( αhν ) 1/2 versus hν plots, where α is the absorption coefficient (calculated from the T and R data) and hν is the photon energy, see Figure D.…”