Synthesis, structural characterization, and magnetic properties of La3+- and Bi3+-Doped Co–Ni–Zn–Cu ferrite nanoparticles

In this study, the synthesis and characterization of new nanoferrites were performed. The structural, morphological and magnetic properties of these materials were enhanced by Fe-site doping. Spinel ferrite nanoparticles with the composition Co 0.3 Ni 0.3 Zn 0.2 Cu 0.2 Fe 2 O 4 along with codoped variants Co 0.3 Ni 0.3 Zn 0.2 Cu 0.2 Fe 1.8 La 0.2−x Bi x O 4 (where x = 0, 0.02, 0.04, 0.08, and 0.12) were synthesized by the coprecipitation method. A comprehensive investigation of their structural, morphological, and magnetic properties was conducted. X-ray diffraction (XRD) confirmed the formation of a cubic spinel structure with a minor hematite phase, which decreased with La 3+ and Bi 3+ . A reduction in crystallite size from 16.69 to 6.67 nm was observed with increasing x from 0 to 0.12. Furthermore, the lattice parameter increased from 8.343 Å in the pure sample to 8.355 Å in the Bi0.12 sample. X-ray photoelectron spectroscopy (XPS) confirmed the oxidation states of constituent elements and indicated that La 3+ and Bi 3+ occupy the octahedral sites. The presence of two bands in the Fourier-transform infrared spectroscopy spectra within the ranges of 500–600 and 385–450 cm −1 indicated the formation of the spinel structure. Energy-dispersive X-ray (EDX) results confirmed that the actual composition of the constituent elements matches closely with the theoretical one. The particle size and lattice parameter , determined through transmission electron microscopy and selected area electron diffraction , were consistent with those obtained from XRD. Magnetic measurements showed a notable reduction in saturation magnetization , coercivity , and remanent magnetization upon codoping ferrite nanoparticles . Codoping with La 3+ and Bi 3+ ions considerably increased the superparamagnetic contribution from 1.27 % to 66.96 % and the paramagnetic contribution from 6.22 % to 32.65 % while reducing the ferromagnetic contribution from 92.51 % to 0.39 %. These results suggest that the nanoparticles can be used in magnetic hyperthermia and magnetic resonance imaging.