Dielectric and magnetoelectric characterization of CoFe₂O ₄/Ba_0.55Sr_0.25Ca_0.2Nb ₂O₆ composites

(1 - x)CoFe₂O₄/xBa_0.55Sr _0.25Ca_0.2Nb₂O₆ magnetoelectric (ME) composites were prepared and characterized. Co-presence of two endmembers was confirmed by SEM and X-ray diffraction analysis. A very high dielectric constant was obtained at low frequencies and an interesting temperature dependence of dielectric constant was observed in the present composite ceramics. All composites after postdensification annealing in oxygen could be electrically and magnetically poled to exhibit significant magnetoelectric effect. The ME effect of the composites was greatly dependent on the frequency of ac magnetic field. With increasing frequency, the magnetoelectric coefficient dE/dH increased firstly and then decreased. dE/dH also depended on the dc bias magnetic field. The highest dE/dH value of 9.51 mV/cm/Oe was observed in 0.2CoFe ₂O₄/0.8Ba_0..55Sr_0.25Ca _0.2Nb₂O₆ composites under 1 kOe and at 90kHz.