Structural transformation and improved dielectric and magnetic properties in Ti-substituted Bi0.8La0.2FeO3 multiferroics

Ti-substituted BiLaFeO3 ceramics having compositions Bi0.8La0.2Fe1-xTixO3 (x = 0.0, 0.05, 0.1, 0.15) were synthesized by the conventional solid-state reaction method. Powder x-ray diffraction investigations performed at room temperature show that the crystal structure is rhombohedral for x = 0.0, 0.05; tetragonal for x = 0.15; and a phase boundary occurs at x = 0.1. In the Rietveld refinement good agreement between the observed and calculated pattern was observed. Dielectric response of these samples was analysed in the frequency range 1 kHz - 5 MHz at different temperatures. A decrease in the values of real (ε′) and imaginary (ε″) parts of dielectric constant with Ti substitution indicates reduced conductivity and hence enhanced resistivity in doped samples. Stability of dielectric constant and conductivity with temperature is considerably improved with Ti substitution. Magnetic measurements were carried out at room temperature up to a field of 20 kOe. Magnetic properties of Bi0.8La0.2FeO3 ceramics are considerably improved on Ti substitution along with a significant opening in the room temperature M-H hysteresis loop. Higher values of remanent magnetization (Mr) 0.1373 and 0.1487 emu g-1; coercivity (Hc) 4.856 and 5.904 kOe are observed for samples with x = 0.1 and 0.15, respectively. This is due to the structural phase transition from rhombohedral to tetragonal. (paper)