Co-substitution induced structural transition with enhanced magnetic and electrical properties of multiferroic BiFeO₃ nanoparticles

Polycrystalline Bi_1−xTb_xFe_1−xCo_xO₃ (for x = 0.05, 0.10, 0.15 and 0.20) nanoparticles were synthesized by tartaric acid assisted sol–gel route. The quantitative crystallographic phase analysis of XRD pattern demonstrates the subsequent structural phase transition from rhombohedral (R3c) to cubic (Pm\(\bar {3}\)m) with the intermediate orthogonal (Pbnm) and orthogonal (Pnma) phase with the gradual increase in concentration of co-substituents. Raman spectroscopic analysis emphasizes that all the co-substituted samples has undergone structural phase transitions which are in good agreement with the results of Rietveld analysis. X-ray photoelectron spectroscopy (XPS) have confirmed that Fe exists predominantly in +3 state in the co-substituted sample. The enhancement in the room temperature magnetic behavior of the sample can be attributed to the co-substitution induced suppression of spatially modulated spiral spin structure of BiFeO₃. All the samples exhibit dielectric anomaly at the vicinity of Neel temperature (T_N) signifies the change in magnetic ordering. Moreover, all the co-substituted samples have been witnessed with reduced leakage current and improved ferroelectric behaviour, which is the desirable characteristics for multifunctional device applications of multiferroics.