A comparative study of magnetic and dielectric behaviors for La1-xBixMn1-yFeyO3 series (with x=0.5, 0.7 and y=0.3, 0.7)

We have carried out an extensive investigation into the effect of doping on both the A-and B-sites for the multiferroic La0.5Bi0.5Mn0.5Fe0.5O3 in relation to its physical properties. The temperature dependent magnetization and dielectric response are determined for different percentages of Bi- and Fe-substitutions. For La0.5Bi0.5Mn0.7Fe0.3O3, there is a prominent ferromagnetic transition T-C around 110 K, whereas the other La0.5Bi0.5Mn0.3Fe0.7O3 and La0.3Bi0.7Mn0.3Fe0.7O3 phases fail to exhibit any clear transition. On the other hand, for the Fe-rich phases, the coercive field increases to 2450 Oe compared to 1720 Oe (for the Mn-rich phase). All the compositions exhibit coexistence of ferromagnetic and antiferromagnetic phases at low temperatures. The temperature dependent dielectric constant of the investigated samples varies from 32 000 to 500 at room temperature and the data has been analyzed using the universal dielectric response model.