Reversal magnetization and dielectric properties in high-entropy multifunctional Gd₁/₅Sm₁/₅Nd₁/₅Pr₁/₅La₁/₅FeO₃ oxide: Optical insights and the role of rare-earth steric hindrance

High-entropy engineering provides a powerful route to manipulate competing interactions in complex oxides. We report the hydrothermal synthesis of a novel high-entropy orthoferrite, Gd 1/5 Sm 1/5 Nd 1/5 Pr 1/5 La 1/5 FeO 3 , crystallizing as a single-phase orthorhombic perovskite ( Pnma ) with high crystallinity. Scanning electron microscopy revealed well-defined box-like microcrystals with random cation distributions and stoichiometric retention of rare-earth elements. Raman spectroscopy showed that increasing disorder promotes the arising, softening, and overlap of vibrational modes, while preserving the principal B 3g (5) breathing phonon associated with the magneto-optic properties of orthoferrites. Diffuse reflectance spectroscopy classified the materials as charge-transfer semiconductors, with direct band gaps decreasing from 2.34 eV to 1.92 eV as configurational entropy increased. Analysis of the optical response using Tanabe-Sugano diagrams revealed a reduction in the crystal field energy of Fe 3+ from 5888.56 cm -1 in GdFeO 3 to 4095.94 cm -1 in Gd 1/5 Sm 1/5 Nd 1/5 Pr 1/5 La 1/5 FeO 3 , accompanied by weakened interelectronic interactions due to coupling between Fe 3+ ( d 5 ) orbitals and the unusual sp 3 d 3 f 2 hybridization of rare-earth ions in a ninefold coordination environment. Magnetization reversal occurs at a compensation temperature (T comp. ) of 23 K due to competition between the Fe 3+ sublattice and the collective rare-earth moments in the presence of high-entropy induced disorder and steric effects. Ionic size mismatch es among the five rare-earth cations generate steric and local strain fluctuations associated with compositional disorder, which modify the Fe–O–Fe bond geometry, effectively tuning the Dzyaloshinskii–Moriya interactions. The dielectric and loss tangent characteristics show Maxwell-Wagner-type interfacial polarization as well as a signal of magnetoelastic coupling at the T N . As expected, the disorder increases the AC conductivity via small polarons as charge carriers . These findings demonstrate that the interplay of configurational entropy and steric effects provides a robust platform for designing next-generation multifunctional orthoferrites with controllable magnetic compensation and coupled optical properties for spintronic and magneto-optical applications.