Enhanced magneto-capacitance in Sr2+ modified BiFeO3–PbTiO3 solid solutions

Abstract

Polycrystalline ceramics of 0.7BiFeO3-0.3 Pb(1-x)SrxTiO3 compositions with x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0 were successfully synthesized by solid state reaction method. The structural, microstructural, ferroelectric, magnetic, dielectric and magnetocapacitive properties have been investigated. X-Ray diffraction analysis using Rietveld refinement revealed the existence of multiphase region with rhombohedral (R3c) and tetragonal (P4mm) polymorphs for x = 0, 0.2, 0.4, 0.6 & 0.8 and single phase with cubic crystallinity for x = 1.0 with Pm3‾m space group. SEM micrographs depicted dense microstructure with non-uniform grains. Except x = 0, pinched ferroelectric loops have been observed for x = 0.2, 0.4, 0.6, 0.8 and 1.0 with low remnant polarization. Sr2+ substitution enhanced the magnetization by suppressing antiferromagnetic spin cycloid of BiFeO3 and the maximum value of remnant was found to be 9.98 memu/g for x = 1.0. Room temperature dielectric studies revealed that the dielectric constant decreases with increasing Sr2+ content in the composition. The magnetoelectric coupling was measured through observing the relative change in dielectric constant induced by applied magnetic field (Magnetocapacitance: MC). The maximum value of magnetocapacitance was found to be 0.88% for the composition with x = 0.6. The magnetic field induced fractional dielectric constant can also be expressed as MC ~ γM2 using Ginzburg–Landau theory and the linear fitting gave the value of positive value of magnetoelectric interaction constant, γ = 3.79, 2.08 and 1.76 for x = 0, 0.06 and 1.0, respectively.