Ferromagnetic and Relaxor-Ferroelectric Properties of Oxygen-Loaded Y_1-xTb_xMnO_3-δ

The magnetic, dielectric, and thermal properties of oxygen-stoichiometric and oxygen-loaded Y_1-xTb_xMnO_3-δ (x = 0, 0.3, 0.5) were studied in polycrystalline and single-crystal forms. Tb substitution induces low-temperature Mn spin-reorientation, attributed to Mn³⁺–Tb³⁺ interactions. In the as-grown samples, dielectric anomalies align with magnetic and spin-reorientation transitions, indicating magnetoelectric coupling. High-pressure oxygen annealing introduces significant amounts of excess oxygen, converting the Mn sublattice from antiferromagnetic to ferromagnetic, with Curie temperatures reaching 78 K. Broad, frequency-dependent relaxor-ferroelectric peaks in dielectric permittivity appear in heavily oxygenated samples, suggesting complex interactions between magnetoelectric and relaxor effects due to Tb substitution and oxygenation. These findings highlight the tunable magnetoelectric properties of hexagonal manganites under oxygen loading, with potential applications in multiferroic and relaxor-ferroelectric devices.