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The Co substitution in Ni-Zn ferrites with respect to their structural and magnetic properties has been investigated in favor to select a material for future electromagnetic interference (EMI) shielding application purpose. Ni 0.6−x Zn 0.4 Co x Fe 2 O 4 (x = 0, 0.03, 0.09, 0.27) nanoparticles were synthesized using a sol-gel method and annealed at 700 • C. The prepared Ni 0.6−x Zn 0.4 Co x Fe 2 O 4 samples were characterized for their structural, stoichiometric, and magnetic properties. X-ray diffraction patterns reveal the formation of single-phase spinel cubic structure formed at x = 0.27. The influence of Co doping on structural properties of Ni-Zn ferrite was examined with X-ray diffraction and field emission scanning electron microscopy. The stoichiometry of prepared samples has also been examined by energy-dispersive X-ray spectroscopy. The magnetic behavior was studied using a vibrating sample magnetometer at room temperature. The variations in values of saturation magnetization were explained on the basis of spin canting effect imparted by hematite (α-Fe 2 O 3 ) phase with spinel phase. Ni 0.6−x Zn 0.4 Co x Fe 2 O 4 with x = 0.27 possesses best saturation magnetization and can be useful in EMI shielding material.

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Cobalt-substituted nickel-zinc ferrite nanoparticles (Ni 0.6-x Zn 0.4 Co x Fe 2 O 4 ) (x = 0, 0.0165, 0.033, 0.264 and 0.528) have been synthesized and characterized with respect to their structural and magnetic properties. Exceptionally in spite of the reported literature where the saturation magnetization increases with Co doping that attributes to Co 2? ions distribution in octahedral sites, the saturation magnetization in our samples decreases by increasing Co contents as revealed by vibrating sample magnetometer measurements. To know the structural properties such as phase identification, measurement of crystallite size and other structural parameters, prepared samples have been performed by X-ray diffraction technique. The X-ray diffraction spectra measurements show that samples have single-phase spinel cubic structure at x = 0, 0.033, 0.264 and 0.528, and at x = 0.0165, there is partial formation of hematite phase. The uncommonly decreased saturation magnetization, variation in retentivity, coercivity and magneto-crystalline anisotropy and also variation in structural properties with Co doping are explained on the basis of Co 2? ions distribution in tetrahedral and octahedral sites in place of Ni 2? and Zn 2? ions having different magnetic moments and different ionic radii, respectively. Using transmission electron microscopy, the particles size has been calculated. The morphology and stoichiometry of prepared samples have been investigated by field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy techniques, respectively. The structural and magnetic measurement results are well co-related with each other with respect to Co 2? ions doping and its distributions. The moderate saturation magnetization and low coercivity values of all samples show soft magnetic behavior and attribute the usefulness of these materials in magnetic recording devices. Graphical Abstract

Here we report, unveiling the active sites for improved electrocatalytic hydrogen evolution reaction (HER) by structural tailoring of Niobium Disulfide (NbS 2). NbS 2 synthesized by chemical vapor deposition method, structural deformation is carried out by post-argon plasma and annealing treatment. Plasma-treated (P.T) NbS 2 exhibits layer-by-layer stacked (≈250 nm) long and (≈200 nm) wide flakes, which show more edge sites and demonstrates low hydrogen evolution activity. Annealed NbS 2 flakes are enlarged in size (≈1 μm) having more surface area which shows additional active basal plane sites and demonstrate remarkable HER performance at 10 mA cm −2. As the thickness of NbS 2 is reduced, more basal planes are exposed hence improved HER activity was achieved. This enhanced electrocatalytic change demonstrates that the basal planes are the main active sites for HER in NbS.