IMF2017

Magnetoelectric materials have been studied for several possible technological applications based in the exploitation of the magnetoelectric effect. In order to enhance the magnetoelectric response, nanoparticles production has been proposed as an alternative for enhancing the magnetic response, and consequently, the magnetoelectric coupling. In fact, the magnetic properties change with decreasing of the particle size and exotic magnetic orders or behavior, as the superparamagnetism, can emerge. In this way, strong magnetic responses may result in a strong coupling between magnetic and electric order parameters in magnetoelectric materials. In this work, nanostructured ceramic bodies (mean grain sizes lower than 50 nm) of BiFeO₃-PbTiO₃ compounds were synthesized by using a modified Pechini method followed by fast-firing. Structural analysis showed single phase materials. A remarkable change in the magnetic order was achieved by a drastic reduction of the nanoparticle size (for paticles of ~10 nm in diameter, observed by Transmission Electronic Microscopy), whereas the magnetic hysteresis loops, obtained by vibrating sample magnetometry, revealed a typical superparamagnetic-like behavior. A phenomenological analysis of the magnetic hysteresis loops strongly suggest that the superparamagnetism is formed by the overlapping of weak-ferromagnetic and paramagnetic contributions of the magnetic ensemble. Finally, the thermal dependence of the electrical properties under external magnetic fields, such as conductivity, resistivity and resistance, was investigated and indicated an ehanced magnetoelectric coupling in these materials.