Preparation, Ferroelectric And Ferromagnetic Properties Of Pb（Zr,Ti）O₃-CoFe₂O₄Nanocomposite Thin Films

Recently, multiferroic materials with ferroelectric, ferromagnetic and magnetoelectric properties have attracted ever-increasing interest due to their widely potential applications, such as sensors, transducers, memories and novel multifunctional devices. To prepare magnetoelectric nanocomposite film, Pb(Zr, Ti)O3(PZT) and CoFe2O4(CFO) are generally used as ferroelectric and ferromagnetic phases, respectively, because PZT has a large piezoelectric effect and CFO has an outstanding magnetostrictive effect However, PZT-CFO nanocomposite thin films annealed by conventional method are easy to occur inter-diffusion and reaction problems between the two phases, which deteriorate the crystal quality and show poor ferroelectric and ferromagnetic properties. On the other hand, the number and thickness of each layer have a significant effect on microstructure of the PZT-CFO multi-layer films, especially the residual strain, which will affect the properties of the entire multi-layer nanocomposite thin film.In this paper, PZT-CFO nanocomposite thin films were first deposited onto Pt/Ti/SiO2/Si substrates by a chemical solution deposition (CSD) method. And then the effects of annealing process (conventional annealing and layer-by-layer annealing) on microstructure, preferred orientation and properties of these films were studied. The results indicated that the PZT-CFO nanocomposite thin films annealed by layer-by-layer annealing were able to achieve columnar growth, obtain a greater grain size and reduce diffusion of elements. Thereby, this thermal processing is effective to improve the ferroelectric and ferromagnetic properties.Moreover, to study the effect of interfacial numbers on the multi-layer films, the nanocomposite films with3layer,5layer and9layer of PZT and CFO were deposited using the same method, and investigated by XRD, AFM, SEM, ferroelectric analyzer and PPMS. These results showed that the lattice constant of PZT and CFO gradually deviated from bulk materials and a significant decrease in grain size with increase in number of layers. Consequently, the ferroelectric property of the composite films progressively deteriorated while ferromagnetic property became better then worse.