INVESTIGATIONS ON THE MULTIFERROIC PROPERTIES OF (BiFe03),_x(BaTiO3)., SOLID SOLUTIONS

Abstract

Multiferroic materials, in which ferroelectricity and some kind of magnetic order occur in the same phase, may present a magnetoelectric effect, offering the possibility of controlling charge via an applied magnetic field, or, conversely, controlling spin via an applied voltage. These materials are suitable to the construction of multifunctional devices, such as electric field controlled magnetic data storage devices, sensors, transducers and spintronics devicesA series of multiferroic (BiFe03)i_ (BaTiO3)z [x= 0, 0.1, 0.2, 0.3, 0.4 and 0.5] solid solution ceramics were synthesised by conventional solid-state reaction with a view to obtaining magnetoelectric properties, i.e. ferroelectric and magnetic activity in the same range of temperatures. Well crystalline phase has been optimized at sintering temperature of 1000°C for 2 hours. The effect of BaTiO3 (BTO) content on structure, magnetic optical, dielectric, ferroelectric, surface morphology and magnetoelectric properties were investigated. X rays diffraction studies of these ceramics revealed change of phase from rhombohedral to cubic for x >0.3. Optical band gap of pure BiFeO3 (BFO) was found to be 2.72 eV which increased with content of BTO. The M-H curve revealed the BFO as antiferromagnetic material whereas, induced weak ferromagnetism was observed for (BiFeO3)i x(BaTiO3)x composites with x=0.1, 0.2, 0.3 and 0.4 at room temperature. The results evidenced the destruction of a space-modulated spin structure in bulk materials, via substituent effects, releasing a latent magnetization locked within the cycloid. Minimum tangent loss is obtained at 0.3 content of BaTiO3. All samples of BF-BT solid solution with different composition exhibit evident ferroelectricity by showing P-E loops. Relative to unmodified BiFeO3, modified BiFeO3-BaTiO3 based ceramics revealed enhancement in the electric-field-induced polarization. Magnetoelectric effect was supplemented by magneto-capacitance in which capacitance changes with applied magnetic field. All composition of (BiFeO3)1-(BaTiO3), ceramics have negative magnetocapacitance similar like most ferromagnetic and antifeiromagnetic materials and show a decrease in dielectric constant. The average grain size of samples was found to be between 1-2 μm. EDXS analysis verified the chemically homogeneity of each element Bi, Fe, Ba, Ti and their relative ratio in (BiFeO3)1_,,(BaTiO3)x solid solution