Experimental and DFT + U investigation of PrFe₂O₄ spinel ferrite: structural, optical, and electronic properties

Abstract

The multifunctional applications of rare-earth spinel ferrites remain limited due to incomplete understanding of their structural–electronic correlations. In this study, we address this challenge by combining experimental characterization and DFT + U calculations to uncover the structural, optical, and electronic properties of PrFe₂O₄. X-ray diffraction confirmed the formation of a single-phase cubic spinel structure (Fd-3 m) with a refined lattice parameter of 8.236 Å and unit cell volume of 558.661 Å3. Crystallite size analysis revealed nanoscale domains (32–43 nm), while SEM showed densely packed micrometer-sized grains, confirming structural densification. Optical measurements identified a strong absorption peak at 950 nm and dual band gaps—an indirect gap of 2.473 eV and a direct gap of 5.453 eV—highlighting broad-spectrum light response. A relatively high Urbach energy (1.941 eV) indicated structural disorder and localized electronic states, correlating with enhanced sub-bandgap absorption. Spin-polarized DFT + U calculations validated the half-metallic nature of PrFe₂O₄, with metallic character in the spin-up channel and semiconducting behavior in the spin-down channel, accompanied by strong spin polarization near the Fermi level. Theoretical optical simulations further revealed anisotropy in dielectric and absorption responses, with the extinction coefficient peaking at 6.5 near 1 eV and a static refractive index exceeding 6. These findings establish PrFe₂O₄ as a multifunctional material with promising potential for spintronic, optoelectronic, and energy-related applications, providing new insights into the structure–property relationship of rare-earth ferrites.