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 cation stoichiometries were synthesized via a classical mixed-oxide method. XRD patterns of all ceramics show reflections of the target phases SryBa1−yNb2O6 and NixCo1−xFe2O4. The influence of stoichiometry of the ferrimagnetic and 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 temperature increases with nickel content. However, the saturation magnetizations as well as the Curie temperatures of the composites 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 accordance with the dynamic magnetostriction coefficient. The evolution of αME of (NiFe2O4)0.3−(SryBa1−yNb2O6)0.7 composites shows an increase with strontium content up to y 0.5. Higher strontium content leads to a significant reducing of αME.