Correlation between lattice strain and physical (magnetic, dielectric, and magnetodielectric) properties of perovskite-spinel (Bi0.85La0.15FeO3)(1-x)-(NiFe2O4)(x) composites

Multiferroic composites are the current research interest due to their multi-functional behavior with promising electrical and magnetic properties compared to single crystallographic phase multiferroic materials. Hence, multiferroic composites of (1-x)Bi0.85La0.15FeO3-(x)NiFe2O4 (x=0 to 0.50) have been investigated by considering Bi0.85La0.15FeO3 as a ferroelectric phase and NiFe2O4 as a magnetic phase. The crystal structure was examined by analyzing the X-ray diffraction (XRD) patterns. Different crystal structure parameters were obtained from the Rietveld refinement of XRD patterns. An increase in the lattice parameters of both Bi0.85La0.15FeO3 (BLFO) and NiFe2O4 (NFO) phases has been observed with the increase in the percentage of NiFe2O4 in the composites. Absorption peaks in Raman spectra shift toward lower frequencies with the increase in the percentage of NFO in the composite. Variation of lattice parameters and shifting of the Raman modes suggest the lattice strain at the interfaces of BLFO and NFO. Theoretical magnetizations were calculated for all composites by using the sum rule (using the magnetization of individual phases) and compared with experimentally observed magnetization. Interestingly, the experimental values of magnetizations of the composites are more than the theoretically calculated ones. It could be due to the lattice strain, which was observed from the XRD and Raman analysis.