IMF2017

The magnetoelectric effect (ME) is a combination of ferromagnetic and ferroelectric orders coupling magnetic and electric fields, which allows controlling the magnetic behavior with an electric signal and vice versa. For multiferroic composites, the ME effect can be explained by an indirect coupling between the ferroelectric and the ferromagnetic phases. The main characteristic of the ME is a peak in the DC magnetic field dependency, associated with the magnetostriction behavior of the ferromagnetic phase. In previous works, we reported that the ME voltage coefficient for composites based on CoFe₂O₄ shows a dependence with the frequency of the AC magnetic field. This effect was related to the trigonal field of the ferrite structure, which changes the magnetoelastic contribution at low temperatures, inducing a step-like behavior in the ME coefficient. In this work, the ME of the composites PMN-PT/CFO and PMN-PT/NFO with different frequencies of the AC magnetic field were studied. The results show that the ME coefficient, at low temperatures (5 K), for PMN-PT/CFO composite presents a hysteresis behavior for frequencies higher than 100 Hz. Contrasting these results, the ME coefficient for the PMN-PT/NFO composite shows the well-known peak-peak related to the magnetostriction coefficient. It was possible to explain the ME hysteresis behavior for the CoFe₂O₄ composite based on energy levels stabilization for each ferromagnetic phase. This effect was attributed to the degeneracy of the energy levels, which comes from the Spin-Orbit coupling, from which the dynamic properties of the magnetoelastic interactions are altered.