Particulate multiferroic Ba0.99Tb0.02Ti0.99O3 – CoFe1.8Mn0.2O4 composites: Improved dielectric, ferroelectric and magneto-dielectric properties

Abstract

In present era, the challenge to design materials which unify multiple order parameters has motived the scientific community to work for multiferroic materials. In this work, the multiferroic particulate composites were fabricated from terbium doped BaTiO3 and manganese doped CoFe2O4. Terbium and manganese dopants improved dielectric and magnetic properties in BaTiO3 and CoFe2O4 respectively. Structural study revealed that doped BaTiO3 and CoFe2O4 crystalized into tetragonal and cubic structures, respectively in composites. In multiferroic composites, a dramatic drop in the unit cell volume of magnetic phase resulted in enhanced strain. The improvement in dielectric constant in composites is explained on the basis of bond and hopping lengths. The Curie Weiss Law ascertained that the dielectric peaks are widened. The calculated activation energy from resistivity measurements revealed insulating behavior of composites. The amphoteric nature of terbium and high resistivity of magnetic phase resulted in ferroelectric hysteresis loops which are free from leakage currents. The magneto-crystalline anisotropy was calculated by the Law of Approach to saturation, and was found to be small in composites, due to quenching of orbital angular momenta of the Co2+ ions by the non-magnetic ferroelectric phase. Temperature dependent magnetic study revealed increase in magnetization during zero field cooling as compared to field cooling, confirming magnetization of one sub lattice decreases at slower rate as compared to another sub lattice. The terbium and manganese doping improved the magneto-capacitance of prepared composites, suggesting the use of these composites in magnetoelectric devices.