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

Highlights: • Particulate multiferroic composites based on Ba_0.99Tb_0.02Ti_0.99O₃ and CoFe_1.8Mn_0.2O₄ were prepared by solid state route. • Decrease in cell volume of magnetic CoFe_1.8Mn_0.2O₄ phase resulted in enhanced strain. • Manganese doping lead to insulating nature and reduced conducting nature of composites. • Terbium and manganese doping improved dielectric constant and magneto-capacitance in composites. • Improved magneto-capacitance depicts that the prepared particulate composites act as novel candidates for magnetoelectric devices. -- 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.