Low Temperature Frequency Dependence of Magnetoelectric effect in PMN-PT/CoFe2O4 and PMN-PT/NiFe2O4 multiferroic composites

Reference	Presenter	Authors (Institution)	Abstract
08-108	Alexandre José Gualdi	Gualdi, A.J.(Universidade Federal de São Carlos); Zabotto, F.L.(Universidade Federal de São Carlos); Garcia, D.(Universidade Federal de São Carlos); Bhalla, A.(University of Texas at San Antonio); Guo, R.(University of Texas at San Antonio); de Camargo, P.C.(Universidade Federal de São Carlos); Oliveira, A.J.(Universidade Federal de São Carlos);	Researches in smart materials have been increasing due to the capability to work with different ferroic orders at the same time in the same material. For example, in a magnetoelectric (ME) material it is possible to control the sample electric polarization with a magnetic field and vice versa. This effect is a good alternative to couple both electric and magnetic systems in many situations as a magnetic field sensor or as a multistate memory device. The characteristic ME effect is a peak in of ME response as a function of a DC magnetic field. This peak is associated with the magnetostriction behavior of the magnetostrictive phase of the composite. Since the ME effect is a dynamic property and it depends on an AC magnetic field, it is necessary to study the dynamic response of the material to understand the mechanical coupling between the two phases. This dynamic response for the ME effect is caused by the dynamic magnetostriction of the magnetic grain material and it is proportional both to the frequency and amplitude of the AC magnetic field. In this work, the magnetoelectric effect of the composites $0.68Pb\left(M{g}_{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right.}N{b}_{\raisebox{1ex}{$2$}\!\left/ \!\raisebox{-1ex}{$3$}\right.}\right)-0.32PbTi{O}_3/CoF{e}_2{O}_4$ (PMN-PT/CFO) and $0.68Pb\left(M{g}_{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right.}N{b}_{\raisebox{1ex}{$2$}\!\left/ \!\raisebox{-1ex}{$3$}\right.}\right)-0.32PbTi{O}_3/NiF{e}_2{O}_4$ (PMN-PT/NFO) are investigated using different frequencies of AC magnetic field (10 Hz and 1000 Hz). The results show that the ME coefficient, at low temperatures (5 K), for PMN-PT/CFO composite present a hysteretic behavior 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 behavior for the PMN-PT/CFO composite. This effect was attributed to the degeneracy in the energy levels due to the Spin-Orbit (SO) coupling causing changes in the dynamics properties of the magnetoelastic interactions.
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