CoFe₂O₄–BaTiO₃ multiferroic composites: role of ferrite and ferroelectric phases on the structural, magneto dielectric properties

Cobalt ferrite (CoFe₂O₄) and Barium titanate (BaTiO₃) nanoparticles have been prepared by the microwave hydrothermal technique at 150 °C/60 min. The synthesized powders have been characterized using transmission electron microscopy, X-ray diffraction (XRD) and fourier transformation infrared spectroscopy. The XRD analysis confirms the formation of desired phase with crystallite sizes 25 nm for CoFe₂O₄ and 20 nm for BaTiO₃. The prepared powders were mixed at different weight proportions to obtain nanocomposites of (1 − x)CoFe₂O₄ + (x)BaTiO₃ (0 ≤ x ≤ 1) and densified at 910 °C/50 min via the microwave sintering process. The presence of two phases (CoFe₂O₄ and BaTiO₃) was confirmed using XRD and field emission scanning electron microscopy (FESEM). Ferroelectric (P–E) and magnetic (M–H) hysteresis loops have been studied at room temperature. In P–E loops, the coercive field and remanent polarization show light asymmetric behaviour with an increase of CoFe₂O₄phase concentration. The M–H loops infer that the magnetic saturation of the composite samples drops with increasing of BaTiO₃ phase concentration. The frequency dependent permittivity and permeability properties have been measured over a wide frequency range (100 kHz–1.8 GHz). The static magneto-electric (ME) voltage coefficient (dE/dH)_H is measured by vary in ME output voltage against the dc-bias magnetic field (H) at room temperature.