Ac electrical conductivity and magnetic properties of BiFeO3–CoFe2O4 nanocomposites

Abstract In this paper we report the synthesis of multiferroic BiFeO 3 (BFO)–CoFe 2 O 4 (CFO) nanocomposites. The XRD and SEM data confirm the formation of both the parent compounds and the composite. All the composite samples show typical frequency dispersion at low frequency. The composite samples possess low dielectric loss. The frequency dependence of ac electrical conductivity curves of the composite samples were fitted using the relation σ ( f ) = σ dc + A ( T ) f n ( T ) . It is observed that at lower frequency range the curve is not well fitted suggesting the contribution of small ac conductivity due to electrode polarization effect along with dc conductivity; however at higher frequency the curves are well fitted confirming the frequency dependence of ac conductivity at higher frequency. Frequency dependent of ac conductivity indicates that conduction occurs due to hopping of small polarons among the localized states. BFO shows weak ferromagnetism with coercivity, H c  = 374 Oe and magnetization, M s  = 0.06 emu/g at 21 kOe. All the composite samples show ferrimagnetic nature and found that there is a decrease in both saturation and remanence magnetization with increase in BFO content. However, there is a variation in coercivity with increase in BFO content and the sample 0.8(BFO)–0.2(CFO) (BF8–CF2) shows maximum H c .