Structure, dielectric, magnetic and magnetoelectric coupling properties of xPbTiO3/(1-x)NiFe2O4 composite ceramics

In this paper, xPbTiO3/(1-x)NiFe2O4 (PTO/NFO, x = 0.1, 0.2, 0.3, 0.4 and 0.5) ceramic composites were prepared by mixing of sol-gel synthesized PTO and NFO powders, followed by their uniaxial pressing and sintering at 1150 °C. The effects of PTO/NFO composition on crystal structure, surface morphology, electrical, magnetic and magnetoelectric coupling properties were studied. XRD results showed that the prepared ceramics contain only PTO and NFO phases without any impurity phase. The samples were relatively dense while the grains were evenly distributed. The dielectric constant and loss varied monotonically with the frequency for different molar ratios. The hysteresis loop of the composites with high amount of high resistance NFO phase (x = 0.1, 0.2) has the shape characteristic for a material with large leakage current. The samples with x = 0.1 showed the largest saturated magnetization, while the sample with x = 0.2 had the maximum remnant magnetization. It was also shown that the polarization was affected by the external magnetic field of 1 mT and the strongest ME coupling (relative polarization change of 15.4%) was observed for the 0.5PbTiO3/0.5NiFe2O4 composite. In addition, the relevant calculation showed that the leakage mechanism may not be the main factor affecting the polarization of the obtained ceramics.