BaFe12–xTixO19 hexaferrites up to x = 2.00 were fabricated in an ordinary ceramic way. Crystal structure parameters were isothermally defined at 300 K from the powder XRD by the Rietveld technique....

Changes in the Structure, Magnetization, and Resistivity of BaFe12–xTixO19

Impact of Gd substitution on the structure, hyperfine interactions, and magnetic properties of Sr hexaferrites

We report the synthesis of Ba05Sr05ZnxZrxFe12-2xO19 (x = 000–100) samples using sol–gel auto combustion method The Rietveld refinement of XRD data indicates a) pure phase formation, b) increase in lattice parameters with composition and c) the absence of undesirable phases such as α–Fe2O3, BaCO3 and SrCO3 FESEM and TEM micrographs reveal an increase in grain size with ‘x’ The broadening of Raman peaks without any peak shift in all the samples indicates that the Zn2+/Zr4+ions are incorporated into Ba05Sr05Fe12O19 without altering the local structure Magnetic measurements reveal that the maximum value of saturation magnetization (Ms) is 6737 emu/g in x = 04 sample The coercivity (Hc) monotonically decreases from 4936 KOe to 1029 KOe with increasing concentration of non-magnetic dopants The dielectric constant values decreases monotonically as function of frequency for all the samples The samples because of their superior magnetic properties could be vital for high density perpendicular recording, high density parallel recording EM shielding and permanent magnet applications

Impact of Zn2+-Zr4+ substitution on M-type Barium Strontium Hexaferrite’s structural, surface morphology, dielectric and magnetic properties

The (110) plane of Co3O4 spinel exhibits significantly higher rates of carbon monoxide conversion due to the presence of active Co3+ species at the surface. However, experimental studies of Co3O4 (110) surfaces and interfaces have been limited by the difficulties in growing high-quality films. We report thin (10–250 A) Co3O4 films grown by molecular beam epitaxy in the polar (110) direction on MgAl2O4 substrates. Reflection high-energy electron diffraction, atomic force microscopy, x-ray diffraction, and transmission electron microscopy measurements attest to the high quality of the as-grown films. Furthermore, we investigate the electronic structure of this material by core level and valence band x-ray photoelectron spectroscopy, and first-principles density functional theory calculations. Ellipsometry reveals a direct band gap of 0.75 eV and other interband transitions at higher energies. A valence band offset of 3.2 eV is measured for the Co3O4/MgAl2O4 heterostructure. Magnetic measurements show the si...

http://absimage.aps.org/image/MAR14/MWS_MAR14-2013-003857.pdf

Epitaxy of polar semiconductor $Co_{3}O_{4}$ (110): growth, structure, and characterization

Monoclinic α‐NaVOPO4 as cathode materials for sodium‐ions batteries: Experimental and DFT investigation

In this paper, rare-earth doped M-type strontium hexaferrite magnetic nanoparticles SrHoxGdySmzFe(12−(x+z+y))O19 (x = y = z = 0.01) have been prepared by the sol–gel combustion method for the first time. The properties of the material were investigated using XRD, FTIR spectroscopy, Raman spectroscopy, SEM, UV-Vis spectroscopy, and VSM. X-ray analysis revealed that a magnetic single-phase was formed with a crystallite average size of 49 nm. FTIR spectra confirmed the formation of the structure of the hexaferrite phase. Raman analysis confirmed the formation of all crystallographic hexaferrite sites. A shift in the octahedral site frequencies and a significant shift were observed at site 12k and 2a, indicating that the doping elements occupied these sites. The SEM analysis showed that the particles were different in shape and slightly agglomerated. The EDS result confirmed the purity of the sample. The calculated band gap from the UV-Vis NIR spectroscopy spectra of the sample was 1.62 eV. The magnetic analysis of the sample material at room temperature revealed a coercivity of 5257.63 Oe, saturation magnetization of 67.72 emu g−1, remanence ratio of 0.52, a maximum magnetic energy product of 1.06 MGOe and Curie temperature of Tc = 765 K. First-principles calculations were conducted on multiple configurations of SrFe12−xXxO19 with x = 0, 0.5 and X = Sm, Gd, Ho. The site preference of each doping element was determined, and the effect of the doping on the structural, electronic, and magnetic properties of the compound was studied. The magnetic properties of this rare earth (Gd, Ho, Sm) doped strontium hexaferrite indicated that this compound could be used in both permanent magnets and water treatment application.

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New nanosized Gd–Ho–Sm doped M-type strontium hexaferrite for water treatment application: experimental and theoretical investigations

ZnFe2-x-yGdxSmyO4 (x = y = 0.01) ferrite nanoparticles with average size of 5 nm are synthesized by the co-precipitation method for the first time. X-Ray Diffractometer (XRD) revealed the formation of single-phase spinel with a high crystallinity. Fourier Transform Infrared (FTIR) confirmed the formation of spinel matrix crystallographic sites and Transmission Electron Microscopy (TEM) confirmed the formation of agglomerated spherical particles with nanometric sizes. The analysis of magnetic properties indicates a week ferrimagnetic behavior at low temperatures, while a superparamagnetic behavior is observed at high temperatures. The blocking temperature value is 55 K. A DFT study was performed on the normal, mixed and Sm–Gd co-doped spinel zinc ferrite using the GGA + U method to evaluate their ground state magnetic spin configuration and the effect of Sm3+ and Gd3+ doping on the structural, magnetic and electronic properties of zinc ferrite nanoparticles. It is found that the nanomaterial is most likely to adopt a ferrimagnetic spin arrangement with a degree of inversion close to 0.5. These results suggest that this material has significant function in the industry, which could be beneficial in point of view for telecommunication applications.

New nanosized (Gd3+, Sm3+) co-doped zinc ferrite: Structural, magnetic and first-principles study

Moroccan non-standard materials are used for the first time to synthesize nanoparticles of Manganese Cobaltite Spinel Oxide (MnCo2O4) at low temperature by the molten salt technique. The products have been characterized to determine their chemical compositions, phases and morphologies. The x-ray Diffraction (XRD) patterns show the formation of a single-phase MnCo2O4 nanoparticles at three different temperatures with a particle size between 29 and 41 nm. Fourier Transform-Infrared spectra (FTIR) analysis confirms the formation of spinel MnCo2O4 without any bands of parasitic phases or impurities, and gives, in good agreement with the results of Thermo-Gravimetric Analysis (TGA), ample information leading to the deduction of the cationic distribution of the products. Moreover, the majority of the elaborated nanoparticles have a polyhedral shape. First principal calculation results show that the inverse spinel structure with a ferrimagnetic ordering is the most stable configuration for MnCo2O4 which agrees with the experimental results.

https://iopscience.iop.org/article/10.1088/2053-1591/aaf447/pdf

Elaboration, characterization and first principle studies of MnCo 2 O 4 nanomaterials prepared from non-standard raw materials

For the first time, the nanoparticles of LiCo2O4 spinel were elaborated at low temperature by a new process using non-standard Moroccan metallurgical grade reagents. Thermogravimetric analysis (TGA) of the as prepared powders was carried out for the determination of decomposition temperature. X-ray diffraction (XRD) patterns confirmed the formation of LiCo2O4 at 400 °C, which has a cubic spinel structure with the space group (Fd3m). The crystallite size and lattice parameters were found to be 19 nm and 8.153 A, respectively, which illustrate the transition of the spinel to the nanocomposite HT-LiCoO2–Co3O4–CoO at 900 °C. The FTIR (Fourier Transform Infrared) spectra showed three fundamental absorption bands (v1, v2 and v3), which are attributed to the stretching vibrations of octahedral and tetrahedral sites, respectively. Particle size, morphology and chemical composition of spinel LiCo2O4 are evaluated using transmission electron microscopy (TEM) coupled with EDS. The EDS spectrum has confirmed the purity of the compound by the presence of Co and O. In addition, first-principles calculations were performed on the spinel material using the Full-Potential Linear Augmented Plane Wave method. The corresponding electronic structure is studied and the Li average voltage is calculated using the GGA+U method with the present work self-consistently calculated Ueff values.

New technique for elaboration and characterization of a high voltage spinel LiCo2O4 cathode and theoretical investigation

For the first time, rare earth doped strontium hexaferrite nanoparticles Sr(1−x)LaxGdySmzFe(12−(z+y))O19 (x = 0.3, y = z = 0.01) were synthesized by the sol–gel combustion method in this paper. A single-phase with space group P63/mmc was confirmed by X-ray diffraction (XRD) and the average crystallite size was found to be 46 nm. The existence of absorption bands of the hexaferrite phase structure was shown by the Fourier transform infrared (FT-IR) spectra. Raman analysis confirms the formation of all crystallographic hexaferrite sites. The effect of the rare earth elements on the nanoparticles’ morphology was evaluated by scanning electron microscopy (SEM) analysis. Energy-dispersive X-ray spectroscopy (EDX) results confirm the sample homogeneity. The value of the band gap was found to be 1.52 eV from the UV-vis NIR spectra. The magnetic analysis of the prepared sample revealed at room temperature a coercivity, saturation magnetization, remanence ratio, maximum magnetic energy product, switching field distribution, and a Curie temperature of 4296.39 Oe, 62.29 emu g−1, 0.49, 7.79 KJ m−3, 0.663, and 490 °C, respectively. These results suggest that this material has a significant function in industry, which could be beneficial for recording media applications. Using first-principles calculations, the site preference of the doping elements Sm, Gd, and La, as well as the effect of doping with these elements on the structural, magnetic, and electronic properties of the M-type strontium hexaferrite, was investigated.

C. Ahmani Ferdi

Papers

New nanosized Gd–Ho–Sm doped M-type strontium hexaferrite for water treatment application: experimental and theoretical investigations

New nanosized (Gd3+, Sm3+) co-doped zinc ferrite: Structural, magnetic and first-principles study

Elaboration, characterization and first principle studies of MnCo 2 O 4 nanomaterials prepared from non-standard raw materials

New technique for elaboration and characterization of a high voltage spinel LiCo2O4 cathode and theoretical investigation

Novel ferrimagnetic nanomaterial Sr(1−x)LaxGdySmzFe(12−(z+y))O19 for recording media applications: experimental and theoretical investigations