Ferromagnetic, ferroelectric and dielectric properties of Pb(Zr0.53Ti0.47)O3/CoFe2O4 multiferroic composite thick films

Abstract

Pb(Zr0.53Ti0.47)O3/CoFe2O4 (abbreviated as PZT/CFO) multiferroic composite thick films have been prepared on the Pt/Ti/SiO2/Si substrate by using a hybrid sol–gel process. The thick films were finally annealed at 650 °C in air and the ferromagnetic, ferroelectric and dielectric properties of these films were investigated. Both the PZT pervoskite phase and the CFO spinel phase were detected from x-ray diffraction. The thickness of the film was measured to be about 3.55 µm using a surface profiler and was confirmed with scanning electron microscopy. Effective saturated magnetization (Mes) estimated from the measured saturated magnetization (Ms) was defined and the result shows that the Mes of the film fabricated in this work is larger than that of the thickest PZT/CFO film reported so far, so are the coercive magnetic fields (Hc). The properties of the films can be attributed to less constraints from the substrate to the composite thick films. The remanent polarization (Pr) of 12.5 µC cm−2 is comparable to that of the thickest PZT/CFO film reported so far due to the lack of polyvinylpyrrolidone (PVP), while the coercive electric field (Ec) of 252.8 kV cm−1 is much larger than it. In addition, the PZT/CFO thick films exhibit a smaller dielectric permittivity of about 200 within the whole measured frequency range due to the introduction of the low dielectric permittivity CFO phase. Furthermore, dielectric loss decreases to ∼0.01 with increasing frequency to 1 MHz, even lower than that of the PZT thick films. Although the ferroelectric properties and the dielectric constant of the PZT/CFO thick film were degraded compared with a pure PZT thick film, the coexistence of a promising ferromagnetic and ferroelectric response with a lower loss indicated that the PZT/CFO film is a good candidate for future applications in a reasonably high frequency range.