Magnetoelectric characterization of xNi0.75Co0.25Fe2O4–(1−x)BiFeO3 nanocomposites

Magnetoelectric (ME) nanocomposites containing Ni0.75Co0.25Fe2O4–BiFeO3 phases were prepared by citrate sol–gel process. X-ray diffraction (XRD) analysis showed phase formation of xNi0.75Co0.25Fe2O4–(1−x)BiFeO3 (x=0.1, 0.2, 0.3 and 0.4) composites on heating at 700 °C. Transmission electron microscopy revealed the formation of powders of nano order size and the crystal size was found to vary from 30 to 85 nm. Dispersion in dielectric constant (ε) and dielectric loss (tan δ) in the low-frequency range have been observed. It is seen that nanocomposites exhibit strong magnetic properties and a large ME effect. On increasing Ni0.75Co0.25Fe2O4 contents in the nanocomposites, the saturation magnetization (MS) and coercivity (HC) increased after annealing at 700 °C. The large ME output in the nanocomposites exhibits strong dependence on magnetic bias and magnetic field frequency. The large value of ME output can be attributed to small grain size of ferrite phase of nanocomposite being prepared by citrate precursor process.