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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]

Ho-substituted Li–Ni ferrites with composition L i 1.2 Ni 0.4 Ho x Fe 2- x O 4 ; 0≤ x ≤ 0.15 were synthesized by a self-ignited sol-gel process. An annealing temperature of 950 °C is estimated via thermal-gravimetric (TGA) analysis. X-ray diffraction (XRD) scans have confirmed the formation of the ferrite phase with a spinel structure in all samples. Substitution of Ho ions on the B-site significantly reduced the porosity from 38 -to 23% and the crystallite size from 23.4 -to 21.7 nm. Microstructural analysis revealed a denser structure with an increase in Ho content. Dielectric results showed that both the dielectric loss and dielectric constant depict a nonlinear variation with the addition of Ho. Complex impedance behavior with a single semicircle for all samples suggests the predominant effect of the grain boundary mechanism. The substitution of Ho ions in place of Fe ions significantly decreased the electrical conductivity. The anisotropic Ho3+ ions reinforce the L-S coupling which consequently enhanced the coercive force from 145 -to 389 Oe, and thus the anisotropy constant. [ABSTRACT FROM AUTHOR]

A series of Cu-Co-substituted manganese ferrites (Mn1-xCuxFe2-yCoyO4; x = 0.0–0.1, y = 0.00–0.25) were synthesized via microemulsion method. The values of structural parameters, i.e., lattice constant and crystallite size, were increased with the inclusion of Co and Cu ions. FTIR studies revealed first band at 400–500 cm−1 and second band at 561–588 cm−1. The values of dielectric parameters have been increased with the increase of Cu and Co concentrations. The magnetic parameters, i.e., saturation magnetization (Ms), coercivity (Hc), and remanence (Mr), have been investigated from M-H loops. The values of Ms and Mr were observed to increase from 5.00 to 36.02 emu/g and from 4.6 to 13.2 emu/g, respectively. The value of coercivity had been decreased from 466 to 261 Oe. The increase in saturation magnetization as well as decrease in dielectric losses proposed that synthesized nanoferrites may be potential candidates for high frequency and microwave applications. [ABSTRACT FROM AUTHOR]

We report the dopant- and size-dependent variations in high-frequency magnetic and electrical transport properties of Ho-substituted Li-Mn polycrystalline ferrites. Thermal stability and phase identification were confirmed by thermal gravimetric analysis and X-ray diffraction experiments. The overall average crystallite size decreased from 29.6 to 17.5 nm, whereas the bulk density increased from 3.47 to 4.29 g/cm 3 with increasing Ho content. Ferromagnetic resonance (FMR) measurements at the X-band revealed significant shifts in FMR linewidths and resonance positions as a function of composition. Both, FMR linewidth and porosity, were found to decrease with the systematic addition of Ho from 2538 to 2359 Oe and from 26% to 15.4%, respectively. The substitution of Ho 3+ for Fe 3+ reduced the net magnetization of the spinel lattice from 53 to 41 emu/g. Electrical measurements revealed that the resistivity is higher in samples with smaller grains possessing a greater number of thin insulating grain boundaries. The activation energy ∆ E required for hopping increases from 0.09 to 0.16 eV with Ho addition, which may be well explained by the increase in resistivity. The substitution of Ho 3+ for Fe 3+ causes a decrease in Curie temperature T c due to the damping of A-B exchange interactions. [ABSTRACT FROM AUTHOR]

In the present study, the impact of holmium (Ho) substitution on structural, spectral, dielectric and magnetic behavior of Li 1.2 Zn 0.4 Ho x Fe 2−x O 4 (0.00 ≤ x ≤ 0.15) ferrites was investigated. The development of spinel phase and structural changes induced by Ho doping were confirmed by X-ray diffraction. The accommodation of Ho ions into spinel lattice was restricted for x ≥ 0.06 as indicated by ortho phase (HoFeO 3 ) traces. The decrease in lattice parameter ( a ) was attributed to the segregation of Ho ions on grain boundaries. FTIR spectra featured two intrinsic vibrational bands v 1 (617 cm −1 ) and v 2 (488 cm −1 ) for x = 0 due to tetrahedral and octahedral vibrations respectively. The compositional dependence of force constants and bond lengths has explained on the basis of cations distribution and oxygen-cation bond distances of respective sites. The addition of Ho ions decreased the saturation magnetization and optimized the coercivity from 59 to 335 Oe, proposing these ferrites for magnetic recording media. Dielectric results for the entire range of frequency (1 MHz to 3 GHz) revealed that ac conductivity increased from 3.5 × 10 5 to 1.8 × 10 6 (Ω-cm) −1 up to x = 0.09 and then it decreased slightly for x = 0.12. The effective contribution of grain-interior mechanism to dielectric behavior was confirmed by complex impedance study. The results of dielectric studies displayed that Ho doped lithium ferrites are suitable low loss potential materials for high frequency based applications. [ABSTRACT FROM AUTHOR]

A comprehensive study on structural, spectral, magnetic and dielectric properties of holmium substituted (Ho 3+ ) lithium ferrites; Li 1.2 Co 0.4 Ho x Fe 2−x O 4 (x = 0.00–0.15) synthesized via auto-citric combustion route has been carried out. The annealing temperature essential for complete decomposition of precipitates and spinel phase formation was found around 950 °C which was estimated from thermo-gravimetric analysis (TGA). The development of face centered cubic (FCC) spinel structure was confirmed from X-ray diffraction (XRD) analysis. However, the traces of an ortho phase (HoFeO 3 ) were appeared for x ≥ 0.06 indicating the solubility limit of Ho 3+ ions. The lattice constant ′ a′ increased from 8.351 to 8.360 Å upon Ho addition up to x = 0.06 and it decreased thereafter from 8.360 to 8.352 Å. This decrease in lattice constant was attributed to the secondary phase formation revealing segregation of Ho 3+ ions at grain boundaries. The porosity was found to decrease from 44 to 23% by the inclusion of Ho 3+ ions. Fourier transform infrared spectra (FTIR) exhibited tetrahedral ( v 1 ) and octahedral ( v 2 ) intrinsic vibrational bands at 627 cm −1 and 479 cm −1 respectively and these bands revealed a shift with increasing Ho concentration. The variations in force constants ( K o and K t ) were calculated and discussed with the tetrahedral (r A ) and octahedral (r B ) bond length trends. The dielectric parameters have been investigated as a function of composition and frequency. The systematic addition of Ho gradually increased the ac conductivity from 8.97 × 10 3 to 5.56 × 10 4 (Ω-cm) −1 up to x = 0.12 and it subsequently decreased for x = 0.15. The complex impedance examination (Cole-Cole plots) confirmed a grain-interior phenomenon, effectively contributing to the dielectric properties. The coercivity was enhanced while the saturation magnetization (Ms) was lessened by the incorporation of Ho 3+ ions. The maximum value of coercivity (706 Oe) was obtained for Li 1.2 Co 0.4 Ho 0.12 Fe 1.88 O 4 . The improved coercivity may suggest their utilization in perpendicular recording media applications. [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]

Co2+ and Mn2+ co-doped lithium spinel ferrites with the chemical composition Li 0.5 Fe 2.5-0.5x Co x Mn x O 4 (x = 0.0–0.5) were fabricated by micro-emulsion method. The spinel structure with face centered the cubic phase was confirmed from the XRD study. The lattice constant was found to increase first from 8.369 to 8.374 Å and then decreased up to 8.367 Å, as the substitution level increased, attributed to the formation of the secondary phases. The crystallite size of nano ferrites was found in the range of 47 to 37 nm. Substitution of Co2+ and Mn2+ significantly enhanced the density of prepared ferrites. FTIR studies revealed the appearance of the characteristic vibration bands of Li 0.5 Fe 2.5 O 4 between 550 and 650 cm−1 which were appreciably influenced by the concentration of Co2+ and Mn2+. The force constants showed an indirect variation with the bond lengths of A- and B -sites. The dielectric properties such as dielectric constant (εʹ), complex dielectric constant (εʹʹ) and tangent loss (tanδ) were analyzed between 1 MHz and 3 GHz. By increasing the frequency, εʹ, εʹʹ, and tanδ were decreased and have shown a dispersive behavior at higher frequencies due to the effect of space-charge polarization. The obtained low values of dielectric loss may refer these materials for applications in transformer cores and high-frequency devices. • Growth of Li0.5Fe2.5-0.5xCoxMnxO4 (x = 0.0–0.5) ferrites by micro-emulsion method. • The lattice constant was found to increase first from 8.369 to 8.374 Å and then decreased. • FTIR studies revealed characteristic vibration bands of Li0.5Fe2.5O4 between 550 and 650 cm-1. • The dielectric properties were analyzed between 1 MHz and 3 GHz. [ABSTRACT FROM AUTHOR]

CoTb 0.03 Fe 1.97 O 4 ferrite and poypyrrole (PPy) polymer nano composites were prepared by mixing the nano crystalline ferrite with poypyrrole (PPy) by following the solid state reaction synthesis route. The XRD patterns of CoTb 0.03 Fe 1.97 O 4 spinel ferrite powders and polymer (PPy) exhibited single phase spinel structure. The amorphous nature of PPy was evidenced by the broad peaks of XRD patterns. The surface morphology unfolded heterogeneous distribution in composites and ferrite. The grains in ferrite were spherical in shape with clear boundaries. The morphology was appreciably altered by the inclusion of ferrite contents. The higher activation energy and resistivity aroused due to blocking of conduction mechanism owing to nanoparticles embedded in the PPy matrix. A downfall in the dielectric loss of the composites is observed as the frequency of the applied field is increased. The incorporation of ferrite contents optimized the magnetic parameters of the composites. The enhanced coercivity (Hc) of these nanocomposites might be beneficial for memory devices. [ABSTRACT FROM AUTHOR]

The substitution of Neodymium (Nd) in the cobalt - zinc (Co–Zn) ferrite was analyzed. The sol-gel technique was used to synthesize the se ceramic samples. The crystalline structural, molecular characterizations, and magnetic properties were analyzed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) experiments, and vibrating sample magnetometer (VSM) respectively. XRD patterns revealed the single-phase cubic spinel structure of the samples. Lattice p arameter varied from 8.41 to 8.38 Å with the inclusion of Nd concentration. The existence of two characteristic frequency bands in the range of 400–1400 cm−1 was confirmed by FTIR spectra. VSM measurements showed the magnetic behaviour at room temperature. The saturation magnetization was noted to decrease from 81 to 66 emu/g with increasing the Nd concentration. The sample having step size x = 0.025 revealed the highest coercivity and retentivity. Dielectric properties were studied and showed variation in dielectric constant, dielectric loss, ac conductivity, and energy dissipation (tangent loss) in the prepared material s. • Auto-citric combustion method was used to prepare Co0·6Zn0.4NdxFe2-xO4 ferrites. • The estimated value of constant lattice decreases upon increasing Nd ions. • Intrinsic vibrational bands revealed a shift with increasing the Nd content. • The porosity of the samples increased from 0.41 to 0.55. • Nd inclusion optimized saturation magnetization and coercivity. [ABSTRACT FROM AUTHOR]

Dy–Ni substituted Mn 1-x Ni x Fe 2-y Dy y O 4 (x = 0.0–0.1 and y = 0.0–0.2) soft magnetic oxides were synthesized using a size controlled micro-emulsion method. X-ray diffraction (XRD) analysis was employed to confirm the spinel structure of synthesized ferrites. Crystallite size was found to decrease (33-22 nm) while lattice constant was increased (8.58–8.63 Å) by increasing dopants content. FTIR bands observed in the range 500–600 cm−1 is the evidence to form the spinel structure of these ferrites. Dielectric constant (ε′) and dielectric loss (ε") were observed to decrease with the increase of frequency due to hopping mechanism. Hysteresis curves exhibited soft nature of synthesized nanoferrites. Remanence (M R) and saturation magnetization (M S) were increased with the incorporation of Dy and Ni ions. The decreased in dielectric losses and increased in magnetic parameters suggested that these ferrites are potential candidates for magnetic recording heads. [ABSTRACT FROM AUTHOR]