RESUMO
The research for lead-free magnetoelectric (ME) multiferroic composite materials has increased considerably because they are environmentally friendly. For composites with 0-3 connectivity, synthesis with lead-free phase has proven challenging to obtain high values of ME coupling. This work reports the successful synthesis of the KNN/CFO composite (K0.5N0.5NbO3/CoFe2O4) by conventional synthesis process. XRD and SEI showed two well-defined, also presenting good electric polarization values. The ME coefficient was very high, reaching values close to 2850 mV cm-1·Oe at the electromechanical resonance frequency. The dipolar interaction between the electric charges and magnetic moments of the KNN and CFO phases was responsible for the high value and the behavior of dependence on the applied magnetic field.
RESUMO
The dependence of frequency and applied magnetic field in the magnetoelectric effect (ME) of the composites 0.68Pb(Mg1/3Nb2/3)-0.32PbTiO3/CoFe2O4 (PMN-PT/CFO) and 0.68Pb(Mg1/3Nb2/3)-0.32PbTiO3/NiFe2O4 (PMN-PT/NFO) are investigated. The results for PMN-PT/CFO composite, show a hysteretic behavior for the ME coefficient, at low temperatures (5 K), for frequencies higher than 1000 Hz. Contrasting with these results, the ME coefficient for the PMN-PT/NFO shows a well-known peak-peak related with the magnetostriction coefficient. Based on energy levels of stabilization for each ferromagnetic phase, it was possible to explain the ME hysteretic distinct behavior of PMN-PT/CFO, because of the degeneracy in the energy levels, due to the spin-orbit coupling causing changes in the dynamic properties of the magnetoelastic interactions.