Magnetodielectric effect in rare earth doped BaTiO3-CoFe2O4 multiferroic composites

Abstract

Magnetically switchable dielectric properties in functional multiferroic composites at room temperature is considered to be a great challenge in order to fabricate magnetoelectric devices. High magnetoelectric effect in such materials is possible provided ferroelectric phase is highly coupled to the magnetic phase. In this report, an attempt has been made to fabricate multiferroic composites (1-x) Ba0.95Ho0.05TiO3 – x CoDy0.1Fe1.9O4 (x = 0.03, 0.06 and 0.09) by solid state route, with tunable magnetodielectric properties. From XRD studies, a decrease in cell volume of CoDy0.1Fe1.9O4 phase is observed with the increase in Ba0.95Ho0.05TiO3 phase, which is responsible for higher magnetodielectric effect. In composites, an appreciable decrease in grain size is one of the main factor that drives the coupling between two ferroic phases. By the incorporation of Ho3+ ions in the BaTiO3 lattice, an increase in ε′ is observed, which resulted in improved magnetodielectric effect in composites. In composites, decrease in hopping length with the increase in ferrite phase, resulted in enhancement in dielectric constant. For all composites, the unsaturated ferroelectric hysteresis loops were observed due to the conducting nature of ferrite phase. The incorporation of Dy3+ ions in the CoFe2O4 expanded its lattice, resulting in strain, which highly affected the magnetic properties. The magnetocrystalline anisotropy of composites with multidomain structure was calculated by using Law of approach to saturation, which is directly related to coupling between two ferroic phases. Magnetodielectric studies revealed that the magnetic ordering of CoDy0.1Fe1.9O4 phase results in increase in number of polar domains of Ba0.95Ho0.05TiO3 phase and thereby improves the magnetodielectric effect. The overall results of this work established the unification of Ba0.95Ho0.05TiO3 and CoDy0.1Fe1.9O4 phases in multiferroic composites, with improved coupling, making them potential candidates for magnetoelectric devices.