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In present research, we employed sol-gel auto-combustion method to synthesize soft ferrites, specifically Ca 0.5 Co 0.5 Cr x Fe 2-x O 4 , with Cr3+ doping, where x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5. As the Cr3+ concentration increased, we observed decrease in both the average crystallite size (from 16.4 nm to 13.5 nm) and lattice constant (form 8.3 Å to 8.2 Å). Notably, the Ca 0.5 Co 0.5 Cr 0.3 Fe 1.7 O 4 sample exhibited the highest AC conductivity at room temperature. Raman spectroscopy confirmed the presence of five active molecular vibrational modes, namely A 1g , E g, and 3T 2g. Direct current (DC) resistivity decreased with the increasing concentration of Cr3+, and the Ca 0.5 Co 0.5 Fe 2 O 4 sample displayed the maximum DC resistivity (6.81 × 108 ohm cm) at a Curie temperature of 383 K. Magnetic properties of soft ferrites, characterized through M-H loop analysis, revealed coercivity values in the range of H C = 1242.6 Oe to 660.8 Oe. These synthesized ferrites exhibit potential applications in longitudinal recording media owing to their performance in the microwave frequency range (6.0 GHz to 13 GHz), consistent DC resistivity, and stable dielectric constant. [Display omitted] • Ca 0.5 Co 0.5 Cr x Fe 2-x O 4 (0.0 ≤ x ≤ 0.5) ferrites were prepared by sol-gel auto combustion. • Dielectric factors exponentially decreased as a function of frequency. • The maximum ac conductivity was revealed by sample x = 0.3 at room temperature. • Maximum DC resistivity (6.8 × 108 Ω-cm) was shown by sample Ca 0.5 Co 0.5 Fe 2 O 4. • Microwave frequency range confirmed the ferrites are best for microwave devices. [ABSTRACT FROM AUTHOR]

Spinel ferrites are attaining huge importance in the modern era, due to their incredible properties, which means they are widely used in various fields. Therefore, in this paper a cost-effective and environmentally friendly preparation of Mg0.25Ni0.25Cu0.5−xCoxFe1.97La0.03O4 (x = 0.0, 0.125, 0.25, 0.375, and 0.5) ferrites via the sol–gel auto-combustion method were carried out. How the structural and functional properties varied with the Cu to Co ratio was studied. It was found that the crystallite size (D) was reduced from 47.2 to 27.6 nm as the Co2+ increased from x = 0.0 to 0.5. While the two major absorption bands including the higher frequency band (υ1) and lower frequency band (υ2) lie in the range of 573.80–538.65 cm−1 and 470.37–405.65 cm−1 belong to the spinel matrix. Five active Raman modes were found in the range of wave number 200–800 cm−1 corresponds to the sublattices of the spinel structure. The optical bandgap increased from 0.85 eV to 1.33 eV for x = 0.0 to x = 0.25 and then observed optical band gap was 1.15 eV and 1.46 eV for x = 0.375 to x = 0.5. The resistivity (ρ) was minimum for Co2+ concentration x = 0.25 at low temperature, while at high temperature the resistivity (ρ) was maximum for Co2+ doping x = 0.25. The temperature coefficient of resistance percentage (TCR %) was −2.66%/K at 513 K for x = 0.25, as shown in the graphical abstract. At lower frequencies, the impedance was observed maximum for Co2+ doping x = 0.125 and minimum for x = 0.375. These findings indicate that the as-prepared ferrites are a potential candidate for optoelectrical and bolometric devices. Highlights: Mg0.25Ni0.25Cu0.5−xCoxFe1.97La0.03O4 synthesis via the sol-gel auto-combustion method. The crystallite size was decreased with Co2+ doping. At high temperatures, the resistivity (ρ) was maximum for Co2+ doping x = 0.25. At lower frequency, the impedance was maximum for Co2+ doping x = 0.125. The temperature coefficient of resistance percentage (TCR%) was −2.66%/K at 513 K for x = 0.25. [ABSTRACT FROM AUTHOR]

Cadmium ferrites belong to normal spinel ferrites, and they exhibit interesting electrical, magnetic, and optical properties. The pure and cerium-doped cadmium ferrites CdFe2−xCexO4 (x = 0.0, 0.125, 0.250, 0.375, 0.5) were synthesized by a chemical co-precipitating technique using sodium hydroxide as a co-precipitating agent. The structures and phase purity of fabricated nanomaterials were analyzed by X-ray diffraction (XRD). The crystallite size for all the prepared nanomaterials was in the range of 28–46 nm. The lattice constant and unit cell volume were found to decrease with the increasing concentration of Cerium, which was confirmed by the peak shift in the XRD pattern. The X-ray density for all nano ferrites increased with the enhancement of cerium composition. The resistivity of the nanomaterials has random behavior with the enhancement of cerium composition for a temperature, but the value of resistivity at x = 0.125 has the lowest value and at x = 0.375 has the highest value for almost all temperatures. For specific concentrations, a decreasing trend of resistivity of fabricated materials was found with an increment of temperature. The activation energies were also calculated, and it increased for x = 0.125 and then decreased for all the nanomaterials. For the confirmation of the M–O bonds, FTIR analysis of all the nano ferrites was also performed. The analysis shows a higher frequency absorption band in the range of 531.24–534.84 cm−1. This absorption band confirms that metal oxides are formed in all the synthesized nanoparticles. [ABSTRACT FROM AUTHOR]

Low temperature and more efficient sol-gel auto combustion process was utilized to synthesize Co 0.3 Li 0.1 Ca 0.5 Fe 2.1- x La x O 4 [ La-CLCF ] spinel ferrites (where x = 0.00, 0.01, 0.02, 0.03, 0.04, and,0.05). The La-CLCF sample's structural, optoelectrical, dielectric, and magnetic properties were examined as a result of La3+ doping. All synthesized La-CLCF samples have single-phased spinel matrix, according to X-ray diffraction (XRD) analysis. It was found that the crystallite size was 11 nm, and the bandgap energy of 3.45 eV for La3+ doping x = 0.03. The resistivity and activation energy both were increased with the substitution of La3+ in the CLCF spinel matrix, while the peak position of temperature coefficient of resistance (TCR) percentage was − 3.92%/K at 372 K for sample x = 0.03. The alternating current conductivity improves with frequency, whereas the dielectric constant and tangent loss decrease as frequency increases. Further, the saturation magnetization and the microwave operating frequency for all the samples were reduced with the doping of La3+. The minimum coercivity was 242 Oe at x = 0.03. Our study suggested that the Co 0.3 Li 0.1 Ca 0.5 Fe 2.07 La 0.03 O 4 sample is tested as an active material for potential use in high-frequency applications, electromagnetic wave absorbing material, and evaluating the sensitivity of infrared (IR) detectors used in night vision bolometers. [Display omitted] • Co 0.3 Li 0.1 Ca 0.5 Fe 2.1- x La x O 4 spinel ferrites preparation via SGAC route. • The peak position of TCR was − 3.92%/K at 372 K for sample x = 0.03. • The minimum coercivity was 242 Oe for La3+ doping x = 0.03 • The sample x = 0.03 is a potential candidate for high-frequency applications, electromagnetic wave absorbing material, and bolometers. [ABSTRACT FROM AUTHOR]

Rare earth cerium (Ce3+) doped Cu 0. 5 Cd 0. 25 Co 0.25 Ce x Fe 2-x O 4 (x = 0, 0.0125, 0.025, 0.0375, 0.05) spinel ferrites nanoparticles were synthesized via co-precipitation technique. XRD, FT-IR, UV-VIS, VSM, LCR and current-voltage measurement techniques were utilized to investigate the structural parameters, metal stretching vibrations, indirect energy band gap, magnetic parameters and electrical behavior of synthesized ferrite powders respectively. The XRD patterns confirmed the remarkable reduction in crystallites size, cell volume and lattice constant while both densities (ρ x , ρ b u l k ) tends to increase with rise in Ce3+contents(x). The indirect energy band gaps (E g) and the DC electrical resistivities were found in decreasing order from 3.48 to 2.50 eV and 9.902 × 107 to 0.142 × 107(ohm-cm) respectively at room temperature (303 K) with Ce3+ doping concentration. LCR meter inveterate that the dielectric constant had declining, and ac conductivity had growing trend at fix value of cerium concentration with rise of frequency from 8 Hz to 8 MHz. The soft magnetic properties can be significantly improved by the small amount of Ce3+ ion doping (x = 0.0375) with an increase of the saturation magnetization (Ms), and retentivity (Mr). [ABSTRACT FROM AUTHOR]

Cadmium ferrites belong to normal spinel ferrites, and they exhibit interesting electrical, magnetic, and optical properties. The pure and cerium-doped cadmium ferrites CdFe2−xCexO4 (x = 0.0, 0.125, 0.250, 0.375, 0.5) were synthesized by a chemical co-precipitating technique using sodium hydroxide as a co-precipitating agent. The structures and phase purity of fabricated nanomaterials were analyzed by X-ray diffraction (XRD). The crystallite size for all the prepared nanomaterials was in the range of 28–46 nm. The lattice constant and unit cell volume were found to decrease with the increasing concentration of Cerium, which was confirmed by the peak shift in the XRD pattern. The X-ray density for all nano ferrites increased with the enhancement of cerium composition. The resistivity of the nanomaterials has random behavior with the enhancement of cerium composition for a temperature, but the value of resistivity at x = 0.125 has the lowest value and at x = 0.375 has the highest value for almost all temperatures. For specific concentrations, a decreasing trend of resistivity of fabricated materials was found with an increment of temperature. The activation energies were also calculated, and it increased for x = 0.125 and then decreased for all the nanomaterials. For the confirmation of the M–O bonds, FTIR analysis of all the nano ferrites was also performed. The analysis shows a higher frequency absorption band in the range of 531.24–534.84 cm−1. This absorption band confirms that metal oxides are formed in all the synthesized nanoparticles. [ABSTRACT FROM AUTHOR]

Tertiary Cu 0.25 Ni 0.15 M 0.25 Co 0.35 La 0.15 Fe 1.85 O 4 (M = Mg 2+ , Mn 2+ , and Cd 2+ ) spinel ferrites powders were prepared using the cost-effective sol-gel auto combustion route. The lattice parameters, absorption and vibrational bands, energy band gap, AC conductivity, and dielectric loss of the as-prepared ferrites were all measured. The Cd2+ doped ferrite has a minimum crystallite size (D) of 50.9 nm, which is smaller compared to Mg2+ and Mn2+ doped ferrites. Furthermore, the X-ray diffraction (XRD), as well as Fourier transform infrared radiation (FTIR) and Raman analysis confirmed the doping of Mg2+, Mn2+, and Cd2+ ions on their respective lattice sites. The resistivity of the divalent ions (Mg2+, Mn2+, and Cd2+) doped ferrites decreased in the para region and increased in the ferro region as the temperature increased. Moreover, the resistivity of the Cd2+ doped ferrite was smaller when compared to the ferrites doped with Mg2+ and Mn2+ ions. From Arrhenius plots, the minimum activation energy (Δ E) 0.8671 eV was observed for Cd2+ doped ferrites. The Cd2+ substituted ferrite also has the smallest AC conductivity and dielectric loss compared to Mg2+ and Mn2+ substituted ferrites. The coercivity and saturation magnetization were 136.41 Oe and 92.29 emu/g for the Cd2+ doped ferrite, respectively. These results suggest that the Cd2+ doped ferrite material could be used in high-frequency and high-power applications. • The Cu 0.25 Ni 0.15 M 0.25 Co 0.35 La 0.15 Fe 1.85 O 4 (M = Mg 2+ , Mn 2+ , and Cd 2+ ) spinel ferrites were prepared. • Minimum activation energy and maximum optical bandgap energy were observed for Cd-CNCL ferrite. • The minimum coercivity and maximum initial permeability were found for Cd-doped CNCL ferrite. • The Cd2+ doped CNCL ferrite exhibits minimum dielectric losses. • The Cd2+ doped CNCL ferrite is best for high-frequency and high-power applications. [ABSTRACT FROM AUTHOR]

Due to their low cost, easy preparation, and outstanding electrical, dielectric, and magnetic properties, spinel ferrites are of enormous scientific and technological importance. Moreover, graphene nanoplatelets (GNPs) are an excellent supporting material for the construction of a wide range of composites. The sol-gel auto combustion (SGAC) route was used to prepare Ni 0.5 Co 0.5 Fe 1.97 Nd 0.03 O 4 (NCNF) ferrite and their composites with GNPs. Single-phase structures were found by X-ray diffraction (XRD) analysis and the crystallite size increased with the insertion of GNPs into the NCNF sample. Raman spectra also confirmed the spinel structure of the ferrites and supported the existence of graphene in the composite. Micrographs indicate that agglomeration decreased in all the samples. It was found for the NCNF/2.5 wt%GNPs composite, the energy bandgap was 1.90 eV, while the temperature coefficient of resistance (TCR) had a value of −4.27 K−1 and the values of the dielectric constant and quality (Q) factor were a maximum. Moreover, the dielectric tangent loss was minimum, and magnetic tangent loss was maximum for the NCNF/2.5 wt%GNPs composite. A saturation magnetization of 108.83 emu/g and 24.06 GHz microwave frequency were observed for NCNF/2.5 wt%GNPs composite. Therefore, the composite NCNF/2.5 wt%GNPs had improved dielectric characteristics making them a promising material for a variety of applications, including microwave frequency operating devices, bolometric devices, and microwave absorbing materials. [Display omitted] • Sol-gel auto combustion was used to synthesize Ni 0.5 Co 0.5 Fe 1.97 Nd 0.03 O 4 /GNPs composites. • XRD and Raman analysis was used to study the structure. • The energy bandgap had a value of 1.90 eV for NCNF/2.5 wt%GNPs composite. • The peak position of temperature versus temperature coefficient of resistance (TCR) percentage plots occurs at 382 K. • The dielectric tangent loss was minimum, and magnetic tangent loss was maximum for NCNF/2.5 wt%GNPs composite. • The NCNF/2.5 wt%GNPs composite promising candidate for bolometric devices, microwave absorbing materials & frequency operating devices. [ABSTRACT FROM AUTHOR]

Lanthanum substituted Mg–Ni–Cu–Co ferrite nanoparticles prepared through the Sol-Gel method were studied using different methods such as XRD, FTIR, UV-VIS, SEM, Raman, LCR, EDX and IV to evaluate the structural, optical and electrical properties. The single-phase cubic spinel structure of the prepared samples was confirmed from X-ray diffraction analysis. The FT-IR spectra indicated two absorption bands, ν 1 and ν 2 that represent the complex Fe3+–O2− at A-site (tetrahedral) and B-site (octahedral) vibration. The optical band gap decreased from 2.48eV to 1.53eV observed by UV–Vis, and matched with the electrical resistivity measurements. Variation in the lattice parameters from XRD, the absorption band (octahedral) from FTIR, the optical energy band gap from the UV–vis data and the DC resistivity demonstrated change in structural, optical and electric properties of Mg–Ni–Cu–Co ferrites nanoparticles due to the addition of the rare earth element La3+. Both the dielectric losses and dielectric constant of the prepared samples decreased due to the La3+ ions doping, and A.C conductivity increased with increasing the value of frequency from 8 Hz to 8 M Hz. The variation in Raman peaks reveals that Raman shift varied due to the La3+ addition. EDX data confirmed the stoichiometric calculations of La3+ions substituted into Mg–Ni–Cu–Co ferrite nanoparticles. [ABSTRACT FROM AUTHOR]