Development of the magnetodielectric properties of BaTiO3-CoFe2O4 multiferroic composites

The lead-free x CoFe2O4 - (1-x) BaTiO3 (x = 0, 0.075, 0.15, 0.225, and 1) composites have been prepared via the solid-state process. The composites' microstructure, dielectric, ferroelectric, ferromagnetic, and magnetodielectric (MD) properties were investigated. Notably, XRD analysis indicates a decrease in the tetragonality factor (c(T)/a(T)) of the BTO phase, accompanied by an expansion of the unit cell as x increases from 7.5 to 22.5 wt%. According to the FESEM images, the CoFe2O4 (CFO) grains are uniformly distributed in the matrix with the formation of no impurity phase. The optimal dielectric properties (dielectric constant (epsilon(r)) similar to 2018 and dielectric loss factor (tan delta) similar to 0.16) and ferroelectric characteristics (saturation polarization (P-S) similar to 12 mu C/cm(2) and remnant polarization (P-r) similar to 10 mu C/cm(2)) are achieved at x = 7.5 wt%, attributed to the minimal presence of the non-ferroelectric CFO phase. By increasing the ferrite content (up to 22.5 wt%), the ferroelectric properties of the samples showed a gradual diminution. Also, from x = 7.5 to 22.5 wt%, a sharp increase in the saturation magnetization (from 3.75 to 11.3 emu/g) and remnant magnetization (from 0.93 to 2.35 emu/g) values was observed, while the coercivity diminished from 475.8 to similar to 272 Oe. The simultaneous observation of two ferroic characteristic hysteresis loops validated the multiferroicity of the composites (x = 7.5, 15, and 22.5 wt%). The maximum MD constant (4.68 %) was measured for x = 22.5 wt% composite at the applied magnetic field of 7 kOe.