Synthesis, structural characterization, and magnetic properties of Ni-Zn nanoferrites substituted with different metal ions (Mn2+, Co2+ and Cu2+)

Three series of nanocrystalline Ni-0.7x,Zn0.3MxFe2O4 ferrites (M = Mn2+, Co2+ and Cu2+; x = 0.0, 0.1, 0.3, 0.5, and 0.7) have been synthesized using the citrate method. Several techniques have been used to investigate the influence of the different dopant ions and their doping levels on the structural and magnetic properties of the Ni-Zn ferrites. X-ray diffraction (XRD) analysis confirmed the creation of a single-phase spinel structure. The lattice parameter was found to increase with increasing Mn2+ and Co2+ ion concentrations, but was not altered by adding Cu2+. The density decreased with increasing concentrations of Mn2+ and Co2+, but increased with increasing Cu2+ content. The average particle size estimated from transmission electron microscopy (TEM) images was found to be in the range 21-41 nm, which revealed the manufacture of nanocrystalline ferrites. Two prominent fundamental absorption bands detected in IR spectra between 370 and 570 cm(-1) can be ascribed to the intrinsic stretching vibrations of tetrahedral and octahedral complexes. The magnetic properties of the present spinel ferrites were measured by means of a vibrating sample magnetometer (VSM) at room temperature. The measurements showed that the saturation magnetization (M-s) for Ni-Zn-Mn ferrite increased from x = 0.0 to x = 0.3, but then decreased upon doping at x = 0.7, whereas a monotonic increase in saturation magnetization was observed for Ni-Zn-Co ferrite. For Ni-Zn-Cu ferrite, M-s decreased from 54.70 emu/g at x = 0.0-35.4 emu/g at x = 0.1 and then increased with further addition of Cu2+ . The variation of M-s with different dopant concentrations can be explained on the basis of Neel's two-sublattice model. Among the investigated series, Ni-0.7x,Zn0.3MxFe2O4 nanoferrites achieved high saturation magnetization and coercive field values, indicating that such compositions may find applications in the field of sensors.