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Nowadays, spinel ferrites are the subject of research as their structural, magnetic, and dielectric properties are quite prominent for applications in the magnetic and electrical fields. In this work, nanoparticles of manganese-cobalt spinel ferrite (Mn0.7Co0.3LaxFe2−xO4), with 0–10% doping variation of lanthanum ions, are prepared by Sol–Gel auto-combustion route. The powder obtained from the synthesis was annealed in a muffle furnace at 600 °C for 4 h. XRD results confirmed the formation of the face-centered cubic (FCC) structure with a space group of Fd3m in La3+ doped Mn-Co based spinel ferrites. The crystallite size was calculated from the Scherrer formula, found in the 9–14 nm range. Surface morphology was performed using SEM, revealing that non-uniform spherical shape grains with agglomeration are observed with the La3+ ions doping. FTIR transmittance versus wave number pattern represents two absorption bands corresponding to tetrahedral and octahedral sites. The electrical properties are investigated in the 1 MHz to 3 GHz frequency range, and obtained results are described using the Maxwell–Wagner model. A decreasing trend in the impedance and dielectric constant is observed with the increasing applied frequency for all concentrations of La. The highest impedance value is found for the sample with La concentration x = 0.15. Electric modulus Cole–Cole plots showed grain and grain boundary contribution to the conduction process. The hysteresis loop from VSM data confirms that the prepared ferrites are soft magnetic materials. The increasing concentration of La3+ ions significantly declines the coercive field and remanent magnetization. According to the findings, the prepared ferrite materials are appropriate for microwave and charge storage applications. On the other hand, La-doped Mn-Co ferrites are an excellent choice for soft magnetic applications such as transformer cores and magnetic storage devices. [ABSTRACT FROM AUTHOR]

Ni0.75Zn0.25Fe2O4 has been modified with Zr and Co in stoichiometry of Ni0.75Zn0.2ZrxCoxFe2-2xO4 (x = 0.00, 0.01, 0.02, 0.03, 0.04) in order to get improved electric and magnetic properties. The samples are synthesized by using sol–gel with auto-combustion method. The XRD patterns show their single-phase cubic spinel, and FT-IR spectra confirm F d 3 ¯ m ( O h 7 ) space group. The lattice parameter initially increased from 8.3253 to 8.3440 Å, thereafter decreasing to 8.3121 Å with increasing doping concentration. The crystallite size increased from 32.238 to 46.299 nm after that it decreased to 30.865 nm on commingle the Zr and Co ions in precursor material. The grain size initially increased from 59.9375 to 92.5675 µm; later gradual decrease was observed up to 56 µm on dilute the stoichiometric equation with Zr and Co ions. On inter-mix of Zr and Co ions in Ni0.75Zn0.25Fe2O4, the X-ray density shows the decreasing trend from 5.3938 g/cm3 to 5.3508 g/cm3. The overall porosity% was observed as in descending order from 11.6945% to 10.4506%. On devalue, the Fe3+ ions with Zr and Co ions in Ni0.75Zn0.25Fe2O4. The crystal catalysis activity (specific surface area) shows decreasing trend with raise of doping ions of Zr and Co in Ni0.75Zn0.25Fe2O4. The wave number for tetrahedral sites and octahedral sites are in increasing trend from 395 to 405/cm to 405/cm and 589 /cm to 603/cm, respectively, on surge of Zr and Co ions in precursor material. The corresponding force constant for tetrahedral sites and octahedral sites shows similar trend from 24.99 N/m to 25.59 N/m and 19.552 N/m to 20.554 N/m on augmentation of Zr and Co concentration. The dielectric constant increased from 1649 to 3210, and the corresponding loss factor shows exact trend from 0.07912 to 0.1965 by the application of external field. The AC conductivity also increased from -13.6970 to -13.0125 with increasing doping concentration. On escalation of adulterate, the saturation magnetization and net magnetic moment decreased from 122.6emu/gm to 74 emu/gm. The permeability is inflating from 67.54 to 139 on injecting of Zr and Co in stoichiometric equation of Ni0.75Zn0.25Fe2O4. The crystal shape anisotropy constant gradually decreased from 1357 erg/cm3 to 246erg/cm3on raising doping concentration in stoichiometric equation. On loading the Zr and Co concentration in sample, the coercive filed (Hc) diminish from 22.137 Os to 6.5705Os. The Y-K angles are raised from 14.66° to 27.19° on swarming the Zr and Co ions concentration in Ni0.75Zn0.25Fe2O4. [ABSTRACT FROM AUTHOR]