Tuning Structural, Optical, and Multiferroic Properties of Y _{1 <b>–</b> <i>x</i>} Gd _<i>x</i> FeO ₃ Orthoferrites through Rare-Earth Substitution: A Low-Temperature Hydrothermal Approach

Rare-earth orthoferrites (ReFeO3) exhibit multifaceted properties, including weak ferromagnetism, potential ferroelectricity, and magnetoelectric coupling. This study systematically investigated Y1–xGdxFeO3 (x = 0.2–1.0) synthesized via hydrothermal methods to understand how Gd substitution tunes these multifunctional properties. X-ray diffraction confirms single-phase orthorhombic structures (Pnma) with lattice expansion proportional to the Gd content, while SEM analysis reveals morphology evolving from flattened rectangles to cubes with increasing substitution. Density functional theory calculations reveal complex bandgap evolution (2.30–2.31 eV) with nonlinear electronic structure changes upon Gd doping, attributed to varying magnetic ordering configurations in the G-type antiferromagnetic structure, validated by UV–visible reflectivity measurements. Magnetic characterization shows enhanced saturation magnetization from 1.87 emu/g (x = 0.2) to 3.53 emu/g (x = 1.0) due to Gd3+ magnetic contributions while preserving canted antiferromagnetism. Notably, Y0.4Gd0.6FeO3 exhibits excellent ferroelectric performance with remnant polarization of 6.23 μC/cm2 at 100 kV/cm. These findings demonstrate effective property tuning through Gd doping, where the enhanced magnetization and tunable bandgap advance orthoferrites for magnetic memory applications and the observed ferroelectric properties enable multiferroic sensing capabilities.