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Ferrites are among the most frequently investigated materials mainly due to interesting and practically different properties. Therefore, easily and cost-effective lanthanum doped Mg 0.5 Cd 0.25 Cu 0.25 Fe 2-x La x O 4 (x = 0.0, 0.0125, 0.025, 0.0375 and 0.05) ferrites were synthesized by a co-precipitation route, a comprehensive characterisation of their structural, optical, electric, dielectric, molecular vibrational, and magnetic properties were carried out. X-ray diffraction analysis confirmed the formation of a cubic spinel structure. Variations in frequency bands were also observed with amplification in optical band gap energy (2.95 – 3.38 eV) due to La3+ ions insertion. The electric resistivity had opposite trends at low and high temperatures with increasing La3+ content. The Curie temperature, activation energy, and drift mobility were also determined to have values consistent with the semiconducting behavior of the soft ferrites. The saturation magnetization (M S) has a maximum value 49.385 emu/g with remanent magnetization (M r) was 34.928 emu/g and coercivity 661.4 Oe for La3+ concentration x = 0.05. The minimum dielectric loss was observed for La3+ concentration x = 0.025. Moreover, the resistivity (ρ) has a maximum value of 7.95 × 104 Ω cm for La3+ concentration x = 0.025. The calculated frequency range of La3+ doped Mg–Cd–Cu ferrites was detected in the microwave range (3.36 – 10.80 GHz), suggesting the potential application of the materials in longitudinal recording media and microwave absorbance. [Display omitted] • La3+ doped Mg–Cd–Cu ferritessamples synthesized via co-precipitation. • The lattice constant increased with La3+ substitution. • At 303 K, for La3+ concentration x = 0.025, maximum resistivity was observed. • Magnetization saturation was increased with La3+ concentration. [ABSTRACT FROM AUTHOR]

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]

This research work analyzes the impact of graphene nanoplatelets (GNPs) on the structural, electrical, dielectric, optical, and magnetic properties of the Ni 0·4 Cd 0·6 Fe 1.97 Sm 0.03 O 4 /x-GNPs (SNCF/GNPs) composites (x = 0 %, 2.5 %, and 5 %) prepared via the sol-gel auto-combustion route. The results revealed that SNCF particles were distributed on GNPs which improved the multifaceted properties of SNCF spinel ferrites. XRD analysis confirmed the FCC spinel structure with a minimum crystallite size (D) of 18.99 nm for sample with 5 wt %GNPs. The DC electrical resistivity decreased from 9.06 × 1011 Ω-cm at 313K to 1.41 × 108 Ω-cm at 673K, revealing the semi-conducting nature of composites. The improved electroconductivity and reduced bandgap energy are observed for samples with minimum resistivity 1.02 × 105 Ω-cm at 673K and 1.70 eV energy, respectively, containing 5 wt %GNPs. Samples show higher permittivity values at low frequency and decreased at high frequency. The maximum ac conductivity is observed for composite with 5 wt %GNPs which is attributed to the hopping mechanism. Finally, the magnetization (Ms) increased from 52.24 to 79.71 emu/g with increasing GNPs contents. Hence, the synthesized composites with 5 wt %GNPs are more favorable than the pure sample for application in waste-water treatment, high-frequency devices, and energy storage devices. • Samarium doped nickel-cadmium spinel ferrites (SNCF)/Graphene nanoplatelets (GNP) composites were successfully synthesized. • XRD analysis revealed the existence of FCC spinel structure in the SNCF/GNPs composites. • The direct band-gap energy of the SNCF/GNPs composites was found in the range of 1.70–1.78 eV. • Improved electrical, dielectric and magnetic properties of prepared composites. • Potential for various applications like wastewater treatment, high frequency devices and energy storage devices. [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]

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]

A series of (Zr–Co) substituted Y-type polycrystalline hexaferrite with composition SrBaNi 2 (ZrCo) x Fe 12-2x O 22 (x = 0.0, 0.25, 0.50, 0.75, 1.0) were fabricated by sol-gel auto combustion method. Pure Y-type single phase formation was achieved at a relatively lower temperature of 1150 °C for 5:30 h. The fabricated nano ferrites were examined by X-ray powder diffraction to confirm the pure single-phase formation of Y-type hexaferrites. An increase in lattice parameters (a& c) was observed by adding Zr4+-Co2+ metal cations. Crystallite size (D) measured in the 48-19 nm range. FTIR spectra clarified iron-oxygen vibrational bands at 417-487 cm−1, which approved the Y-type hexaferrites formation. DC electrical resistivity has an opposite trend at high and low temperatures with increasing Zr4+-Co2+ content (x). DC electrical resistivity values depend on grain size; they have an inverse relation. Activation energy, drift mobility, and Curie temperature were also determined. Conduction is due to the hopping of electrons below the Curie temperature, and polarons are responsible for hopping above the Curie temperature. Activation energy varies from 0.39 to 0.10 eV with the substitution of Zr4+-Co2+ ions. A wide frequency range of dielectric characteristics (1 MHz–6GHz) was observed, and these parameters revealed a considerable fluctuation with the substitution of Zr4+–Co2+ ions. Dielectric constant, dielectric loss and ac conductivity of nano ferrites materials increased with frequency and Zr4+-Co2+ content (x). Complex impedance spectroscopy formalism using the Cole-Cole plots indicated that most dielectric responses arise from grain boundary contributions. [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]

Present work reports the synthesis of RE3+ (La3+, and Ce3+) and Co2+ co-doped Zn 0.75 Cu 0.25 Fe 2 O 4 samples powder using sol-gel auto combustion process. Rietveld refinement established the spinel matrix with the space group (F d -3 m) and suggests that the uniform distribution of cations at the tetrahedral and octahedral lattice sites. The comparative study of crystallite size (D) was found using the Scherrer's relation, Scherrer's plot, Williamson-Hall (W–H), and Size-Strain (SS) plot methods for the as-prepared ferrites. The absorption band analysis confirmed the characteristic band absorptions lie in the frequency range of (577.82–418.84) 102 × m−1. Moreover, the electrical resistivity (ρ) measurements showed that the Co–Ce doped ZCF sample is highly resistive as compared to the other samples. The dielectric measurements revealed a dispersion pattern at lower frequencies and an almost frequency-independent pattern at higher frequencies. The field dependence of the dM/dH curve shows a magnetically well stable state and good crystallization cubic matrix of all the samples. The field dependence of the dM/dH curve at 303 K suggests that the increasing peaks separation and height for the as-prepared ferrites are owing to the existence of good magnetic stability and crystallization. [Display omitted] • Sol-gel auto-igniting process used to prepare RE3+ (La3+, and Ce3+) and Co2+ co-doped Zn 0.75 Cu 0.25 Fe 2 O 4 samples powder. • Rietveld refinement confirmed uniform distribution of cations. • The microwaves operating frequency (ω m) lies within the range of 5.31–10.91 GHz. • Well, crystallization and magnetic stability of all the as-prepared samples. [ABSTRACT FROM AUTHOR]

Lanthanum doped Z n 0.5 C o 0.5 L a x F e 2 − x O 4 spinel ferrites were synthesized through the co-precipitation technique. To characterize the structural, vibrational, electro-optical, dielectric, and thermoelectric properties, the following characterization techniques X-ray diffraction (XRD), Fourier transformation infrared (FTIR) and Raman spectroscopy, I–V measurement analysis, UV–vis spectroscopy, LCR meter, Seebeck analysis, and Energy dispersive X-ray analysis (EDX) were used. The XRD patterns showed nano-crystalline single-phase structure formation. Moreover, the lattice constant increased from 8.3909 ± 0.0042 Å to 8.3994 ± 0.0042 Å, and the crystallite size reduced from 33.6 to 17.5 nm with increasing La3+ cations. The bond angles showed stronger A – A and A – B interactions and weak B – B interactions with the addition of La3+. FTIR spectra showed the existence of the M − O stretching band and functional group study. The resistivity, optical band gap, and activation energy had maximum values at x = 0.1. At room temperature (RT), the dielectric parameters were recorded between the range of 8 Hz to 8 MHz. The Seebeck voltage coefficient was obtained for the as-prepared nano-ferrites to determine the charge carrier type. The EDX spectra showed a compositional distribution of the elements in all the samples. • Z n 0.5 C o 0.5 L a x F e 2 − x O 4 nano ferrite powder was prepared via the co-precipitation route. • Single-phase crystal structure and crystallite size decreased with La3+ in Zn–Co ferrites. • The optical band gap and DC resistivity were maximum at x = 0.1. • Z n 0.5 C o 0.5 L a 0.1 F e 1.9 O 4 has a small dielectric tangent loss at low frequency. [ABSTRACT FROM AUTHOR]