Spinel ferrites are materials that have technological and industrial applications. In this study Neodymium (Nd3+) substituted Co–Zn spinel ferrites (CZNF) with chemical formula Co0.7Zn0.3NdxFe2−xO4 with the contents of (x = 0.00–0.20 with a 0.05 difference) was synthesized through sol–gel auto combustion method. The structure of the single-phase formations was verified by using X-ray diffraction (XRD). Moreover, in CZNF samples the crystallite size decreased as the Nd3+ concentrations increased, except for the x = 0.15 sample. Moreover, by using XRD and Fourier transform infrared spectroscopy, the Nd3+ substitution into CZNF spinel ferrite was confirmed. Using image-J software for microstructural analysis, it was discovered that adding Nd3+ ions to CZNF caused an increase in particle size from 7 to 35 nm. It was noted that using UV–visible (UV–Vis) spectroscopy the optical energy band gap (Eg) was maximum at x = 0.00 and minimum for x = 0.20 by additions of Nd3+ to the CZNF samples. The AC conductivity and dielectric constant of CZNF improved with the increase of Nd3+. The addition of Neodymium (Nd3+) ion also decreased the dielectric tangent losses in CZNF spinel ferrites. The saturation magnetization and microwave frequency for x = 0.00 were a maximum of 82.22 (emu/g) and 18.14 GHz, and for x = 0.20, they were a minimum of 25.01 emu/g and 5.48 GHz, respectively. They are prospective materials for a variety of applications because of their dielectric and magnetic qualities, including bolometric devices, microwave absorption materials, and microwave frequency operating devices.Graphical abstract: The graphical abstract presents the synthesis process of pure and modified Co–Zn spinel ferrites by sol–gel auto-combustion technique. The prospective materials for a variety of applications because of their dielectric and magnetic qualities, including bolometric devices, microwave absorption materials, and microwave frequency operating devices.