Magnetoelectric, dielectric, and magnetic investigations of multiferroic NixCo1−xFe2O4−SryBa1−yNb2O6 composites

Magnetoelectric (NixCo1-xFe2O4)0.3-(SryBa1-yNb2O6)0.7 composites with a 0–3 connectivity and different cationstoichiometries were synthesized via a classical mixed-oxide method. XRD patterns of all ceramics show reflectionsof the target phases SryBa1-yNb2O6 and NixCo1-xFe2O4. The influence of stoichiometry of the ferrimagneticand ferroelectric phase on the magnetoelectric behavior was studied on composites with composition of(NixCo1-xFe2O4)0.3-(Sr0.5Ba0.5Nb2O6)0.7 and (NiFe2O4)0.3-(SryBa1-yNb2O6)0.7. The magnetic Curie temperatureincreases with nickel content. However, the saturation magnetizations as well as the Curie temperatures of thecomposites are always lower than the ones of bulk NixCo1-xFe2O4 samples. The maximum magnetoelectric coefficient(αME) rises with increasing nickel content from 40 (x = 0) to 180 μV Oe-1 cm-1 (x = 1) in accordancewith the dynamic magnetostriction coefficient. The evolution of αME of (NiFe2O4)0.3-(SryBa1-yNb2O6)0.7 compositesshows an increase with strontium content up to y 0.5. Higher strontium content leads to a significantreducing of αME.