Tunable coercivity and size and shape dependent magnetic properties in multiferroic barium titanate-cobalt ferrite (BaTiO3@CoFe2O4) nanostructures

BaTiO₃@CoFe₂O₄ nanostructures were synthesized using four facile low-temperature protocols involving coprecipitation, hydrothermal, and in situ hydrothermal routes to achieve controlled particle size and morphology. X-ray diffraction, FESEM, TEM, HRTEM, and BET analyses confirmed the formation of crystalline BaTiO₃@CoFe₂O₄ nanostructures with spherical, nanosheet, and cubic core–shell morphologies. Magnetization measurements at 100 K and 300 K revealed ferromagnetic behavior for all samples. The saturation magnetization ranged from 19 to 31 emu g⁻¹, while the coercivity varied from 32 to 11,716 Oe depending on particle size and morphology, demonstrating highly tunable magnetic properties. The highest saturation magnetization was obtained for the cubic core–shell nanostructures, whereas the spherical nanostructures exhibited the lowest coercivity, indicating excellent soft magnetic characteristics. The variation in coercivity was successfully explained using the random anisotropy model, which revealed a direct dependence on particle volume and an inverse dependence on the surface-to-volume ratio. These results demonstrate that low-temperature synthesis provides an effective route for tailoring the magnetic properties of BaTiO₃@CoFe₂O₄ nanostructures, making them promising candidates for multifunctional magnetic and spintronic applications.