Insights into the effects of Mn substitution in CoFe₂O₄ nanoferrites involving high-frequency storage device applications

Nanoferrites of the CoMn_xFe_(2–x)O₄ series (x = 0.00, 0.05, 0.10, 0.15, 0.20) were synthesized in this study using the sol–gel auto-combustion approach. The lattice constants were computed within the range of 8.312–8.406 Å, while crystallite sizes were estimated to range between 55.20 and 31.40 nm using the Scherrer method. The different functional groups were found to correlate with various absorption bands using Fourier transform infrared (FTIR) spectroscopy. Five active modes were identified by Raman spectroscopy, revealing vibration modes of O²⁻ ions at tetrahedral and octahedral locations. The ferromagnetic hysteresis loop was observed in all the synthesized samples, which can be explained by Neel’s model. The results showed that AC conductivity decreased with increasing Mn²⁺ content at the Fe²⁺ site, while the dielectric constant and dielectric loss increased with increasing frequency. Furthermore, the saturation magnetization (M_s), remnant magnetization (M_r), and coercivity (H_c) all showed declining trends with the increase in Mn²⁺ doping. Finally, the CoMn_0.20Fe_1.8O₄ samples showed M_s and M_r values ranging from 73.12 to 66.84 emu/g and from 37.77 to 51.89 emu/g, respectively, while H_c values ranged from 1939 to 1312 Oe, after which coercivity increased. Thus, the CoMn_0.20Fe_1.8O₄ sample can be considered a promising candidate for magnetic applications.