Fabricação e Caracterização de Heteroestruturas Magnetoelétricas do Sistema Pb(Zr0,2Ti0,8)O3/CoFe2O4 Obtidos Por RF-Sputtering
Bonini, Ricardo Pereira
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This dissertation aims to develop new nanostructured magnetoelectric composites systems based on magnetoelectric effect. The magnetoelectric coupling in nanostructured systems has attracted interests mainly due to possibility of integration between ferroelectricity and ferromagnetism through the handling of electric and magnetic order by cross coupling between electric and magnetic fields. Through an experimental approach (synthesis, processing and characterization) the fabrication process was investigated by the RF-Sputtering technique and the characterization of heterostructured multiferroic composite materials of Pb(Zr0.2Ti0.8)O3/CoFe2O4 were performed. The ferroic and multiferroic properties were investigated for both the separately constituted phases and the heterostructured systems. In this work, the interface between phases has a significant role for the existence of coupling between the different phases, which variations of the ferroelectric and dielectric properties in the heterostructured system were correlated to strain and/or stress at the interface between the phases. In this case, a tensional stress arose in the CFO phase due to the presence of the PZT phase, resulting in an improvement of magnetic properties in case of perpendicular fields to the film surface applied. It was also possible to determine the existence of magnetoelectric coupling, since an improvement in the ferroelectric properties was observed under the presence of a magnetic field of ~5 kOe. Finally, it was reported the magnetodielectric coupling is enhanced in the dielectric dispersion region due to competition between the compressive stress in the PZT phase generated by CFO phase and the changes of electric polarization due to the ME coupling.