Crystal structure transformation, dielectric and magnetic properties of Ba and Co modified BiFeO3 multiferroic

Bi0.8Ba0.2Fe1−xCoxO3 ceramics have been prepared by solid-state reaction method. XRD and Rietveld studies revealed the phase transformation from rhombohedral (R3c, x ⩽ 0.01) to tetragonal (P4mm, x > 0.01). Dielectric constant (ε′) and dissipation factor (tan δ) measured in the frequency range 1 kHz to 5 MHz at different temperatures showed dispersive behavior at low frequencies. A small amount of Co concentration improved the stability of ε′ against temperature. Co addition resulted in an increased frequency independent dc plateau within the measured frequency window. The values of exponent 's' lie in the range 0 ⩽ s ⩽ 1 and follows the correlated barrier hopping model. M-H hysteresis loops were recorded at room temperature up to a field of 15 kOe. Ba and Co substitution transformed antiferromagnetic BiFeO3 into ferromagnetic. The enhanced saturation magnetization with Co addition is closely related to structural phase transition and modification of the antiparallel spin structure.