Characterization and magnetic properties of Nd_xBi_1−xFe_0.95Co_0.05O₃ nanopowders synthesized by combustion-derived method at low temperature

Nd_xBi_1−xFe_0.95Co_0.05O₃ (x=0, 0.05, 0.10, 0.15) nanopowders were prepared by a combustion-derived method. The Rietvelt fitting of the X-Ray diffraction data from the Nd_xBi_1−xFe_0.95Co_0.05O₃ (NBFCO) powders showed nanopowders with rhombohedral BiFeO₃ crystalline structure (R3c) for x≤10 and a partial structural transition to orthorhombic phase (Pnma) for x=0.15. The differential thermal analysis and thermogravimetric analysis (DTA/TGA) showed a crystallization temperature of 180 °C. Transmission electronmicroscopy (TEM) images revealed that the NBFCO nanopowders were composed of fine particles under 60 nm. From Raman spectroscopy, a band of disordered anion lattice was observed at 653 cm⁻¹. In spite of the antiferromagnetic nature of bulk BiFeO₃, the NBFCO nanopowders obtained displayed a ferromagnetic hysteresis loop, with coercivity about 0.1 T and remanent magnetization of 1.02–4.33 A m²/kg were obtained at room temperature. This ferromagnetic behavior is due to increasing and uncompensated spins at the surface and the canted internal spin by the tilt of FeO₆ octahedral units. We have developed a novel synthetic route for the preparation of ferromagnetic BFO-derived nanopowder materials by a surfactant-assisted combustion-derived method. - Highlights: • The structure of materials obtained is studied. • A new synthesis method was proposed to obtain ferrimagnetic–ferromagnetic BiFeO₃ nanoparticles. • Synthesis temperature does not exceed 200 °C. • The obtained nanoparticles have sizes less than 52 nm