Nd and Sc co-doped BiFeO3 nanopowders displaying enhanced ferromagnetism at room temperature

We have developed a novel synthetic route for the preparation of single phase NdxBi1 − xFe0.95Sc0.05O3 (NBFSO) nanopowder materials by a surfactant-assisted combustion-derived method. Rietveld fitting of the Powder X-ray diffraction data showed the nanopowder structure evolves from a distorted rhombohedral BiFeO3 crystalline structure (R3c, x = 0) to a orthorhombic structure (Pbnm, x = 0.10). Differential thermal analysis and thermogravimetric analysis (DTA/TGA) showed a crystallization temperature of 200 °C. Transmission electron microscopy (TEM) images revealed the presence of clusters formed by fine nanoparticles less than 60 nm in diameter. From Raman spectroscopy, the change from rhombohedral structure to cubic structure was observed by a drastic intensity reduction of the A1−2 and A1−3 Raman modes, with the A1−1 and A1−2 modes gradually merging together, indicating the merge of the orthorhombic phase. Despite the antiferromagnetic nature of bulk BiFeO3, the NBFSO nanopowders obtained displayed a ferromagnetic hysteresis loop, with coercivities of 0.08 T and remanent magnetizations of 0.65-4.05 Am2/kg when measured at room temperature. The increasing and uncompensated spins at the surface of nanoparticles and the canted internal spin by the tilt of FeO6 octahedral units and the structure transition appear to be the main reason for observed this ferromagnetic behavior.