Synthesis and magnetic characterization of novel CoFe2O4–BiFeO3 nanocomposites

The novel mixed spinel–perovskite nanocomposites of xCoFe2O4(1 − x)BiFeO3 (x = 0.1, 0.2, 0.3, 0.4) have been prepared by sol–gel technique. The structure and morphology of the composites were examined by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), and electron diffraction (ED). The XRD and TEM results showed that the composites consisted of spinel CoFe2O4 and perovskite BiFeO3 after annealing at a temperature higher than 400 °C, and the crystal size ranges found to vary from 20 to 80 nm. Vibrating sample magnetometer and magnetoelectric measuring device were used to characterize the magnetic properties and the ME effect of the nanocomposites. It is shown that the nanocomposites exhibit high magnetic properties and a ME effect. The nanocomposites with composition 0.3CoFe2O40.7BiFeO3 annealed at 700 °C exhibited the largest coercivity (Hc) of 1351 Oe and the optimal squareness (Mr/Ms) of 54%. The saturation magnetization (Ms) and coercivity (Hc) increase drastically with the increase of CoFe2O4 concentration in the nanocomposites when annealed at 700 °C. The ME effect of the nanocomposites strongly depends on the magnetic bias and magnetic field frequency.