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The substitution of rare earth ions is a novel approach to vary the dynamic magnetic properties of soft ferrites to such an extent that its electrical properties and ferromagnetic resonance (FMR) response can be set over a broad frequency range. In this work, a complete transmission electron microscopy (TEM), scanning electron microscopy (SEM), ferromagnetic resonance spectroscopy (FMR), X-ray photoelectron spectroscopy (XPS), and current-voltage (I-V) analysis of holmium (Ho) substituted lithium-nickel soft ferrites with composition Li 1.2 Ni 0.4 Fe 2−x Ho x O 4 (x = 0, 0.03, 0.06, 0.09, 0.12, and 0.15) is carried out. TEM analysis reveals a spherical shape distribution of nanoparticles with a particle size of ∼ 50 nm. FMR study is carried out to check the role of Ho addition on magnetic energy losses, FMR line position, and shape. The shift in FMR line shape is mainly attributed to the anisotropy contribution, relaxation processes, and ferromagnetic interactions between the magnetic nanoparticles. XPS experiments confirm the presence of all compositional elements along their valence states. The Ho substitution increased the electrical resistivity, whereas the damping of A-B exchange interactions resulted in a decline of Curie temperature (T c), which is required for high-frequency power applications. • TEM study of Ho-doped Li-Ni ferrites revealed an average particle size of ∼ 50 nm. • XPS experiments confirm the presence of all compositional elements along their valence states. • Enhanced electrical resistivity and a decline in Curie temperature as a function of Ho were observed. • FMR losses were reduced by replacing the Fe ions with Ho ions required for high-frequency power 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]

Ni 0.5 Sn 0.5 Co x Mn x Fe 2−2x O 4 ferrites with x = 0.0–0.8 have been prepared by the micro-emulsion method, using CTAB as a surfactant material. X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR) and vibrational sample magnetometer (VSM) were used to investigate the effects of Co and Mn substitutions on cationic distribution, crystallite size, lattice constant, spectral, magnetic and dielectric properties. Lattice constant and crystallite size were found to increase from 7.4 to 9.25 Å and from 11.8 to 19.7 nm respectively with increasing substitution of Co and Mn ions. Saturation magnetization (M S ) gradually increased from 20.5 to 47.6 emu/g with increase in the value of x. However, Coercivity increased from 152.7 to 462.4 Oe up to x = 0.4 and then it decreased thereafter. The dielectric constant, complex dielectric constant and tan loss (tanδ) were observed to decrease with increase in frequency, depicting the semiconductor behavior of the ferrites. Dc resistivity was observed to decrease considerably upon addition of Co and Mn content. The outcome for the tunable magnetic properties and achieved modification of the synthesized nanocrystallites may be chosen for tremendous applications; such as miniaturized memory devices that are based on the energy storage principles and capacitive components. [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]

Antiperovskites have gained huge interest due to their distinctive physical, chemical, and thermodynamic properties. They are electronically inverted perovskites that turned out to be a growing class of versatile materials, providing a dynamic and effective research field to materials scientists. The present work is designated to study significant physical properties of novel antiperovskites XCRh 3 (X = Cd, Ta, W, Re, Os, Ir, Pt, Au, Hg, Ce, Pr, Nd, Pm, Sm, Eu, Tb) using density functional theory based first-principles approach. This study includes the investigation of the structural, electronic, elastic, magnetic, and thermodynamic properties of the presented antiperovskites. Both the paramagnetic and ferromagnetic phases have been considered for computing the formation energy of compounds to elaborate the structural and mechanical stability. The spin-polarized electronic properties of ferromagnetic stable compounds demonstrated metallic features at the Fermi level in both spin versions. The mechanical parameters related to macroscopic properties, i.e., Young's modulus, Bulk modulus, shear modulus, tetragonal shear modulus, Poisson's ratio, Pugh's ratio, Cauchy's pressure, Zener anisotropic factor, lubrication factor, and compressibility factor have also been computed. The quasi-harmonic Debye model has been employed to analyze various important thermodynamic properties under a broad range of pressure (0–50 GPa) and temperature (0–1400 K). [ABSTRACT FROM AUTHOR]

• Sol-gel route was used to prepare Ba 3 Co 2-x Mg x Fe 24 O 41 hexaferrites. • The occupancy of Mg2+ ions at the octahedral site was altered by Fe3+ ions. • The dielectric permittivity was decreased by incorporating of Magnesium. • Cole – Cole plots revealed a single semi-circle. • Magnetic investigations unfolded ferrimagnetic nature of all samples. The Ba 3 Co 2-x Mg x Fe 24 O 41 hexaferrites were prepared by the sol–gel combustion route. The materials were annealed at 1350 °C and displayed the single-phase characteristics. X-ray density (D x) decreases owing to increasing Mg-concentration. Crystallite size was calculated with the help of Debye Scherrer's formula and found within the 17–18 nm range. Fourier transform infrared spectroscopy was used to determine the specific absorption peaks of hexagonal ferrites. It was executed in the region of 420–700 cm−1—the occupancy of Mg2+ ions at the octahedral site at delayed alternation of Fe3+ ions. As a result, the dielectric permittivity decreased. The grain boundary contribution was clearly seen in synthesized ferrites' cole plots. The cole – cole plots show a single semi-circle which reveals that grain boundaries play a significant role in the conduction process. Magnetic measurement indicated the ferrimagnetic behavior of all samples. [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]

A series of holmium (Ho) doped nanocrystalline Ni 0.7 Zn 0.3 Ho 2x Fe 2–2x O 4 ; 0.0≤x≤0.07 ferrite was synthesized using the conventional ceramic technique. The cubic spinel structure was confirmed by powder X-ray diffraction (XRD). The lattice parameter increases with increase in Ho content due to large ionic radius of Ho 3+ (0.901 Å) as compared to Fe 3+ (0.67 Å). Room temperature DC electrical resistivity and activation energy both increase with the increase of holmium contents. The saturation magnetization (M s ) decreased gradually from 78.92 to 54.17 emu/g due to holmium ions substitution in Ni-Zn ferrites. This decrease in M s is explained on the basis of redistribution of cations amongst the sites and weakening the A-B exchange interactions. An increase in electrical resistivity made this material suitable for its use in high frequency device applications. [ABSTRACT FROM AUTHOR]

• Sol-gel technique was employed to synthesize Ba 4 Cu 2-x Ni x Fe 36 O 60 ferrites. • Cole-Cole plots markedly distinguished grain boundary contribution. • Coercivity (H c) increased (1844.44–2946.83 Oe) by increasing Ni contents. • The squareness ratio (0.471–0.450) revealed single magnetic domain. • The results suggest their potential use in high-frequency applications. This paper reports the impacts of nickel substitution on dielectric, magnetic, and structural characteristics of Ba 4 Cu 2-x Ni x Fe 36 O 60 hexaferrites prepared via the sol–gel method. The sample was annealed for 5 h at 1200 °C. The crystalline structure, magnetic and dielectric features were examined by X-ray diffraction, vibrating sample magnetometer, and impedance analyzer individually. The specific absorption bands of hexagonal ferrites were identified by FTIR spectroscopy and in the 420–600 cm−1 range. M−H loops of samples were determined to examine the magnetic properties of synthesized materials. Magnetic measurement shows that samples exhibit ferrimagnetic behavior at room temperature. The magnetic properties are described in cation distribution and grain size effect. Dielectric properties of the samples were observed in the frequency range (1–3 GHz). Cole-Cole graphs of prepared materials revealed the influence of grain boundaries. A single semi-circle in the impedance Cole-Cole plots approves a special part of grain boundaries in the conduction process. Dielectric properties are affected by the electron hopping mechanism between Fe2+ and Fe3+ ions. These performances expose that these nanomaterials are appropriate for high-frequency applications. [ABSTRACT FROM AUTHOR]