Magnetic, dielectric and magnetoelectric properties of BiFeO3-CoFe2O4 nanocomposites

Nanocomposites (NCs) comprising BiFeO3 (BFO) and CoFe2O4 (CFO) with nominal composition, x CoFe2O4 - (1-x) BiFeO3 (x = 0.2, 0.3 and 0.4) have been synthesized adopting a sol-gel route. XRD patterns of the prepared samples exhibit presence of both BFO and CFO crystalline phases. TEM images of the NCs show that particles are mostly spherical with size in the range 15-25 nm. Room temperature Mössbauer spectra of the pristine samples and NCs reveal presence of Fe3+ ions at different inequivalent sites of BFO and CFO. Room temperature dc magnetization measurements show significant enhancement in magnetization of the NCs compared to that of the pristine BFO. Variation of dielectric constant of the NCs with frequency shows a dispersive behavior in low frequency region which is attributed to grain boundary relaxation in the NCs. εr - T curves of all samples exhibit an anomaly near the antiferromagnetic transition temperature of BFO indicating presence of magnetoelectric (ME) coupling. Variation of capacitance of the NCs in presence of external magnetic field confirms an improvement of ME coupling in BFO after formation of the NCs.