This study reports the synthesis and characterization of nanocrystalline Ni0.5Co0.2Zn0.3BixFe2-xO4 (x = 0.00, 0.025, 0.050, 0.075, 0.100) ferrites synthesized via the sol-gel auto combustion method. The structural, morphological, electric, dielectric, and magnetic properties of Bi3+-doped Ni–Co–Zn spinel ferrites annealed at 700 °C and further sintered at 850 °C, have been investigated towards analyzing the effect of Bi3+ doping. X-ray diffraction (XRD) patterns and Fourier Transform Infrared Spectroscopy (FTIR) spectra have revealed the single-phase cubic-spinel structure of all inspected materials while retaining their high crystalline nature. Their average crystallite size and average grain size are found in the nanoscale range (48–74 nm) and (46–67 nm), respectively. The saturation magnetization (Ms) and experimental magnetic moment (ηexp) are found to decrease with increasing Bi3+ content. The samples sintered at 850 °C display higher AC resistivity, attributing to the reduction of electrons hopping through grains in the samples. The low coercivity values (23.68–87.71 Oe) are observed, classifying the investigated materials as soft ferromagnetic. The increased magnetic anisotropy (K) through Bi3+ doping indicates tunable stability in magnetic orientations, making them suitable for spintronics applications.
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