Effect of Ni substitution on the crystal structure and magnetic properties of BiFeO3

In this paper, BiFe1−xNixO3 (x = 0, 0.05, 0.10, 0.15, 0.20, and 0.25) nanoparticles were synthesized by a sol–gel process X-ray diffraction (XRD), and Raman technique analysis showed that a rhombohedrally distorted BiFeO3 structure with compressive lattice distortion induced by the Ni substitution at Fe sites. Superconducting QUantum Interference Device (SQUID) results showed that, compared with BiFeO3 prepared under similar conditions, the magnetic properties were significantly enhanced at room temperature. The enhanced ferromagnetism was attributed to the size confinement effect of the nanostructures, the ferromagnetic exchange between the neighboring Fe3+ and Ni3+ ions, and the changing of the Fe–O–Fe bond angle. Superparamagnetism with blocking temperature of 10 K for BiFe0.95Ni0.05O3, 75 K for BiFe0.85Ni0.15O3, 125 K for BiFe0.80Ni0.20O3, and 200 K for BiFe0.75Ni0.25O3 was also observed.

► BiFe1−xNixO3 (x = 0.05, 0.10, 0.15, 0.20, and 0.25) nanoparticles are prepared by sol–gel method.
► Structural refinement reveals all the samples were rhombohedral structure.
► The enhanced magnetization was attributed to the suppression of the cycloidal spin structure.