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The nanoparticle spinel ferrites Mg0.5Zn0.5CexLaxFe2-2xO4 (x = 0.0, 0.0125, 0.025, 0.0375, 0.05) were synthesized by mean of co-precipitation method. These magnetic nanoparticles were sintered at 750 °C for 8 h. XRD patterns confirmed the formation of the cubic spinel structure of prepared nanoparticles. The lattice constant of nanoparticle ferrites increased, while crystallite size decreased with doping content (x). Pure ferrite sample has an optical bandgap of 2.61 eV, and it increases from 1.73 to 2.17 eV as concentration (x) is changed from 0.0125 to 0.05. The electrical dc resistivity is of the order of 1010 Ω cm for doping content (x) from 0 to 0.0375 and has a maximum value of 5.48617 × 1012 Ω cm for content x = 0.05. The Curie temperature (Tc) decreased 433–373 K as concentration (x) was increased. The dielectric constant, dielectric loss, and impedance are reduced with the increase of frequency. The dielectric constant, as well as the dielectric loss diminished while impedance increased as doping of cerium and lanthanum, was increased. [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]

Due to their outstanding properties, low cost, and environmental friendliness, mixed transition metal oxides are frequently used in various applications. In this study, Ce3+ doped CdFe 2 O 4 powder samples were prepared through the co-precipitation process. A peak shift was observed towards a lower 2 θ angle with the substitution of Ce3+ at their lattice site and the lattice constant has a maximum value for the x = 0.06 sample with the crystallite size of 34 nm. Moreover, for x = 0.06 sample, the resistivity was found in the order of 106 Ω cm and the dielectric tangent loss had a smaller value. The electrical and dielectric analysis of the as-prepared x = 0.06 sample indicate that it is the best for high-frequency applications. • The Ce3+ doped CdFe 2 O 4 samples were prepared via the co-precipitation route. • The crystallite size was found 34 nm for a sample having Ce3+ x = 0.06 sample. • The x = 0.06 sample resistivity was observed in the order of 106 Ω cm. • The dielectric tangent loss has a smaller value for the x = 0.06 sample. • The electrical and dielectric properties suggested that x = 0.06 sample is suitable for high-frequency applications. [ABSTRACT FROM AUTHOR]

Technology important ferrites ceramic Sr 2 Ni 2 Ga x Fe 12-x O 22 (x = 0.00, 0.2, 0.4, 0.6, and 0.8) samples were produced using sol-gel auto combustion route. Structural, electrical, dielectric, and magnetic parameters were identified by substituting Ga3+ at the Fe3+ site. It was recognized that an increase of Ga3+ content in (Sr 2 Ni 2 Ga x Fe 12-x O 22) ceramic samples first decreased, then increased lattice parameters, and the density of samples was observed. This is because of the ionic radii and atomic weight of Ga3+ and Fe3+ cations. FTIR spectra show two characteristic absorption bands at 444-513 cm−1 caused by metal-oxygen vibrations. Due to the contribution of smaller grains of samples, the higher values of resistivity were observed, which vary from 3.78 × 1010 (Ω cm) to 1.13 × 1011 (Ω cm) by the substitution of Ga3+ ions at the octahedral site. The activation energy was measured between 0.20 and 0.61 eV. The dielectric response of Ga3+ substituted ferrite ceramic samples were studied in the 1 MHz-6 GHz frequency region. The Maxwell-Wagner bilayer model studied the effect of polarization with applied frequency on dielectric parameters. With the substitution of Ga3+, minimal losses in the range 0.34–0.44, about 6 GHz, and a high Q-value of about 10,000 were observed for each sample. In impedance spectroscopy analysis Cole-Cole plots confirm that the dielectric response is because of the influence of grain boundaries. The substitution of Ga3+ enhances saturation magnetization (68.20–71.78 emu/g) while coercivity decreases (655.86–507.86 Oe). In the present finding, the low dielectric loss, moderate permittivity, high value of the Quality factor, and very high value of resistivity of about 1.13 × 1011 that reduces the eddy current losses suggested that these materials are appropriate candidates for many high-frequency applications such as multilayer chip inductor, dielectric resonators, power applications, and microwave devices. [ABSTRACT FROM AUTHOR]

The impact of holmium (Ho) ions on lithium-rich spinel ferrites is studied through magnetic, morphological, and electrical transport properties. The X-ray photoelectron spectroscopy (XPS) analysis indicated the existence of all metal ions in the required valence state. Transmission electron microscopy (TEM) analysis exhibited nano-crystalline (∼50 nm) structures of these ferrites. The electrical resistivity measurements showed the higher resistivity values of the synthesized samples. The resistivity increased from 2.4 × 108 to 2.1 × 1010 Ω-cm with Ho inclusion, indicated an inverse relation with the size of grains. The Curie temperature (T c ) observed to decrease from 848 to 806 K with the incorporation of Ho 3+ ions. The activation energy (Δ E a ) noted to vary between 0.21 and 0.23 eV. The drift mobility (μ d) study revealed a decrease from 1.86x10 −12 to 6.14x10 −14 cm 2 V −1 s −1 by increasing Ho amount up to x = 0.06. A reduction in thermoelectric power (S) from - 143 to -95 μ.V/K by increase in Ho concentration confirmed the Fe replacement by Ho on octahedral B-sites. The ferromagnetic resonance (FMR) investigations indicated a drop in FMR line-broadening (ΔH) from 2491 to 2000 Oe by the increase of Ho concentration, making it beneficial to reduce microwave losses. A non-linear variation in the resonance field (H res) with the substitution of Ho was observed between 7359 to 7785 Oe. [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]

We investigate here the effect of holmium on Li–Co nano-ferrites to elaborate the surface morphology, dynamic magnetic and electrical transport properties. The transmission electron microscopy (TEM) technique was employed to examine the microstructure and grain size distribution. TEM analysis confirmed the nanocrystalline nature (~50 nm) of the prepared materials. X-ray photoelectron spectroscopy (XPS) experiment results verify the presence of all metal ions with the required valences. Ferromagnetic resonance (FMR) analysis revealed the need for a dense microstructure to cut down the microwave losses. FMR line width was observed to reduce from 2757 -to 1676 Oe except for x = 0.12 by the substitution of Ho ions which correspond to low microwave losses. The dc resistivity results show that high resistivity values are associated with smaller grains of the samples and vice versa. Resistivity values are found to increase from 3.66 × 108 -to 5.31 × 108 Ω-cm by increasing the Ho addition. Seebeck experiment revealed n-type conduction. Together with showing the nature of charge carriers, a decrease in the Seebeck coefficient with increasing Ho ensured the replacement of Fe ions by Ho ions on B-sites. [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]