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    Hydrothermal synthesis of CoyZnyMn1-2yFe2O4 nanoferrites: Magneto-optical investigation
    (Elsevier Ltd, 2018) Asiri, Sarah Mousa; Sertkol, Murat; Güner, Sadık; Güngüneş, Hakan; Mujasam Batoo, Khalid; Saleh, Tawfik A.; Sözeri, Hüseyin; Almessiere, Munirah Abdullah; Manikandan, A.; Baykal, Abdulhadi
    Manganese ferrites nanoparticles (NPs) substituted with both Co2+ and Zn2+ simultaneously (CoyZnyMn1-2yFe2O4 NPs for y=0.0 to 0.5), have been produced by hydrothermal approach. The substitution with both Co2+ and Zn2+ ions on the structure, spectroscopic and magneto-optical properties of nanocrystalline MnFe2O4 spinel ferrites have been analyzed in detail. The formation of spinel phase and structural changes induced by Co2+ and Zn2+ ions substitutions were confirmed by X-ray diffraction studies. Rietveld refinement revealed the cubic spinel phase for all products (minor amount of Fe2O3). Lattice constant and crystallite size were found to decrease from 8.478 to 8.370 Å and from 14.68 to 8.22 nm, respectively with increasing substitution of Co2+ and Zn2+ ions. HR-SEM and HR-TEM micrographs revealed the high homogeneity cubic structure of samples. The hyperfine magnetic field values for all products after Mn2+, Zn2+ and Co2+ ions substitution were determined by Mössbauer analysis. The estimated optical Eg (Energy band gap) values are in the range of 1.41–1.54 eV for the samples. The smaller Eg values are mainly attributed to greater particle size and decreasing quantum confinement effect. © 2017 Elsevier Ltd and Techna Group S.r.l.
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    Substitution effect of Cr 3+ on hyperfine interactions, magnetic and optical properties of Sr-hexaferrites
    (Elsevier Ltd, 2018) Slimani, Yassine; Baykal, Abdulhadi; Amir, Md.; Tashkandi, N. A.; Güngüneş, Hakan; Güner, Sadık; El Sayed, H. S.; Aldakheel, F.; Saleh, Tawfik A.; Manikandan, A.
    Chromium-substituted strontium nano-hexaferrites, SrCrxFe12-xO19 (0.0?? x???1.0), were produced by the hydrothermal route. The structure, morphology, optical and magnetic properties were studied. Crystal structure, spinel phase and functional groups were verified using X-ray diffraction and Fourier Transform Infrared spectroscopy. The average crystallites size is ranging between 50 and 67?nm. Scanning electron microscopy observations indicated that the multi-grains of the particles are aggleromated and are hexagonal in shape. The isotherm plots obtained from the nitrogen physisorption experiments showed that the mesopore area and the total pore volume decreased progressively with increasing the Cr3+ content. Besides, the band gap energy (Eg) decreases from 1.75 to 1.43?eV. The magnetic hysteresis loops showed that the produced nano-hexaferrites exhibit hard ferromagnetic-like (FM) behavior. Compared to the pristine SrFe12O19 product, the deduced saturation (Ms) and remanent (Mr) magnetizations, the coercivity (Hc) and the magnetocrystalline anisotropy field (Ha) increase for lower Cr3+ content (x???0.4) and then decrease as the Cr3+ content further increases. The squareness ratio Mr/Ms are ranging between 0.5 and 0.6, suggesting the single domain nano-sized particles with uniaxial anisotropy for various synthesized products. Mossbauer analysis was done to determine the quadrupole splitting, the isomer shift, and the hyperfine magnetic field values of all products.