Structural and magneto-optical coupling in LaCoO₃–MnCo₂O₄ perovskite–spinel heterostructures

This study reports the synthesis and structural characterization of a novel LaCoO₃-MnCo₂O₄ perovskite-spinel heterostructure, with a focus on its magneto-optical coupling properties. Pervoskite and spinel oxides are prepared individually through a hydrothermal technique and then composited using ball milling while maintaining spinel oxide doping levels of 2.5% and 5%. X-ray diffraction confirms intimate interfacial coupling between rhombohedral LaCoO₃ and cubic MnCo₂O₄ phases, which indicates the formation of well-defined heterojunctions. Optical reflectance spectra exhibit an enhanced near-infrared to visible band edge with an energy band gap of 4.2 eV due to perovskite-spinel charge transfer. Photo luminescent spectra showed a broad emission band in the UV–visible spectrum, ranging from 300 to 600 nm, indicating effective charge transfer across the heterojunction and attributed to interfacial defect states. Magnetic studies demonstrate that the MnCo₂O₄ spinel prompted the composites to transition from paramagnetic to weak ferromagnetic behaviour using exchange interactions. These findings demonstrate how hetero-structural interfacing, defect-induced PL emission, and spin-charge interactions synergize to provide multifunctional optical and magnetic properties and promising for applications in magneto-optical sensors, isolators, and integrated spintronic-photonic devices.