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Tungsten trioxide (WO 3 ) thin films have been prepared via sol-gel spin-coating technique for different concentrations of Al (0, 3, 6, 9 and 12 wt.%) and investigated them by structural, optical, dc electrical and Al:WO 3 /p-Si heterojunction diodes. The XRD analysis reveals that the trivalent impurity of Al effectively influences the WO 3 . The UV–vis analysis shows an increase in the Al dopant that caused the band gap energy (E g ) to decrease. The SEM analysis shows that the size of the plate-like grains has reduced the Al:WO 3 thin films. The composition ratio of W, O and Al elements has been confirmed by EDX spectrum. The dc electrical conductivity analysis has identified that Mott’s 3D variable hopping (VRH) mechanism influences the Al:WO 3 thin films. The Al:WO 3 /p-Si p - n heterojunction diode parameters of ideality factor (n), barrier height (Φ B ) and series resistance (R s ) have been calculated using the J-V method. From the current density-voltage-temperature (J-V-T) analysis, the inhomogeneity of barrier heights was extracted using the thermionic emission mechanism with Gaussian distribution (GD) function. As a result, the 9 wt.% of Al:WO 3 /p-Si diode gives better results compared to the other Al:WO 3 /p-Si diodes. [ABSTRACT FROM AUTHOR]

New organic non-linear optical (NLO) single crystals of guanidinium cinnamate were crystallized by solvent evaporation solution growth technique and the crystal and molecular structure were determined by single crystal X-ray diffraction. The crystal packing is dominated by classical N-H···O hydrogen bonding interactions. Due to deficiency of acceptor atoms compared to the donor sites, two unusual ring R (6) motifs are formed through two N-H···O hydrogen bonds. These ring motifs are further connected through chain C (6) or C (8) motifs along the b-axis of the unit cell. Further, these chain and ring motifs are cross-linked through another N-H···O hydrogen bond leading to classical ring R (8) motif. These chain and ring motifs are interlinked with each other to form secondary ring R (14)/R (16) motifs. The molecular geometry of the asymmetric part of the unit cell was optimized theoretically by density functional theory using the B3LYP function with 6-311 + + G(d,p) basis set. The optimized molecular geometry and computed vibrational spectra are compared with experimental results which showed significant agreement. The intermolecular interactions of the title compound were analyzed by the Hirshfeld surfaces. The computed hyperpolarizability values showed that the compound is a good candidate for NLO applications. The chemical hardness, electro-negativity and chemical potential of the molecule were computed by HOMO-LUMO plot. The lower band gap of the frontier orbitals indicates the suitability of fabrication of the material for non-linear optoelectronic applications. [ABSTRACT FROM AUTHOR]

The jet nebulizer sprayed tungsten doped molybdenum trioxide (WMoO3) thin films and its P-N junction diode parameters have been studied for different doping concentrations (0, 3, 6 and 9 wt.%) of tungsten (W). The prepared films were studied by XRD, SEM, EDX, UV and I-V. The structural analyses of XRD and SEM revealed that the WMoO3 films depicted the orthorhombic structure in polycrystalline nature and showed the sub-microsized plate and flake-like structures on the surface. The presence of the elements such as W, Mo and O in the WMoO3 films prepared by jet nebulizer spray (JNS) pyrolysis technique was confirmed by the EDX spectra. From UV-vis analysis, the absorbance decreases up to 3 wt.% of WMoO3 then increases. 3 wt.% WMoO3 film exhibited the minimum band gap energy. The electrical property from I-V represents that the maximum average conductivity obtained as 5.70169 × 10-12 S/cm for 3 wt.% WMoO3 film. From the I-V measurements in darkness and under the illumination, the different diode parameters of ideality factor (n), barrier height (Fb) and sheet resistance (Rs) of n-WMoO3/p-Si were examined using J-V, Cheung's and Norde methods. [ABSTRACT FROM AUTHOR]

Nanocrystalline ε-FeN and γ′-NiFeN (0.2 ≤ x ≤ 0.8) nitride materials are synthesized in pure phase via sol-gel-mediated oxide precursors. The materials are characterized using XRD, SEM (EDX), and magnetic measurements. ε-FeN and γ′-NiFeN (0.2 ≤ x ≤ 0.8) materials crystallize in hexagonal and cubic structures, respectively. The lattice parameters are estimated to be a = 4.7812(36) Å and c = 4.4232(31) Å for ε-FeN and in the range of 3.7922(10)-3.7957(3) Å for various γ′-NiFeN (0.2 ≤ x ≤ 0.8) materials. The values of the lattice parameters show increasing trend up to x = 0.6, showing a peak, and thereafter decreases with the increase in Ni weight percent in γ′-NiFeN (0.2 ≤ x ≤ 0.8) materials. The average crystallite sizes are in the range of 31-54 nm and confirm the nanocrystalline nature of the materials. The SEM particle sizes are in the range of 153(7)-250(14) nm. For pure ε-FeN, the values of saturation magnetization ( M) and coercivity ( H) are 12 emu/g and 225 Oe, respectively. With the progressive substitution of Ni atoms, hexagonal ( ε-phase) changes to cubic ( γ′-phase) at the same reaction temperature, which is evident from the increase in M and H values, i.e., in the range of 144-181 emu/g and 76-109 Oe, respectively, for γ′-NiFeN (0.2 ≤ x ≤ 0.8) compounds. The values of the saturation magnetization for γ′-NiFeN (0.2 ≤ x ≤ 0.8) are found to increase with the increase in Ni content in the materials up to the value of x = 0.6 and decrease thereafter. These results have been interpreted in terms of size and shape effects in nanomaterials including lattice strain and surface effects. [ABSTRACT FROM AUTHOR]

Nanocrystalline nickel oxide (NiO) and cobalt doped NiO have been prepared successfully by a simple chemical method. NiO and cobalt doped NiO nanoparticles have been characterised using various analytical techniques such as X-ray diffraction, FESEM, HRTEM, UV absorption and M-H curves. The average grain size of NiO nanoparticles and cobalt doped NiO nanoparticles are 12 and 9.5 nm respectively. The UV absorbance study shows a strong absorption peak present between 328 and 363 nm. The band gap values of NiO nanoparticles and cobalt doped NiO nanoparticles are 3.58 and 3.78 eV. The incorporation of cobalt into NiO nanoparticles have strongly influenced the magnetic behaviour and the material got converted from super paramagnetic to ferromagnetic material. [ABSTRACT FROM AUTHOR]

In this paper, CoRuFeX (X = Si, Ge) alloys were investigated by means of x-ray diffraction, Mössbauer spectroscopy, magnetic and magneto-transport measurements. Alloys are found to be exist in Y-type structure with presence of some B2 disorder. High values of Curie temperature ( T C ) of 867 K and 833 K are obtained for CoRuFeSi and CoRuFeGe alloys, respectively. The obtained T C values are found to be highest among all the equiatomic quaternary Heusler alloys. The saturation magnetization ( M S ) values are found to be in good agreement with the values obtained from Slater-Pauling estimation, which is a prerequisite for half-metallic ferromagnets. Electrical resistivity in the temperature range of 5–300 K gives an indirect evidence of half-metallic behavior in these alloys at low temperatures. Considering high T C and the transport behavior, both these materials seem to be interesting for spintronic applications. [ABSTRACT FROM AUTHOR]

The present investigation reveals the synthesis of capped nano-crystalline FexCo1−x (0.2 ≤x≤ 0.8) alloys via a superhydride reduction route using oleic acid and oleylamine as stabilizing agents. The synthesized nano-particles are stable against oxidation in an air atmosphere (air stable) at room temperature (298 K). The structure–property correlation in FeCo alloys has been achieved using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), magnetic and Mössbauer measurements. A FTIR study indicates the presence of organic content at the surface of the nanoparticles, which helps in the stabilization of the FeCo samples in an air atmosphere. FeCo alloys crystallize in a pure α-phase with the increase in the values of lattice parameters with the increase in Fe content, i.e. 2.836(±4) Å, 2.852(±2) Å, 2.859(±1) Å and 2.868(±1) Å for x = 0.2, 0.4, 0.6 and 0.8, respectively. Average crystallite sizes and TEM particle sizes were found to be in the range of ≈23–38 nm and 11–51 nm, respectively. The values of the saturation magnetization (Ms) for FeCo alloys range from 71.1–92.5 emu g−1 for heat treated materials and 93.1–142.2 emu g−1 after applying the corrections for organic wt% at the surface of the materials. The observed values of effective anisotropy constants (Keff) of FexCo1−x alloys from field cooled (FC) and zero field cooled (ZFC) studies (i.e. 1.5 kJ m−3, 4.6 kJ m−3 and 14.3 kJ m−3 for x = 0.4, 0.6 and 0.8, respectively) reveal the contribution from the reduced particle size and surface anisotropy. The maximum value of a hyperfine field for FexCo1−x alloys was found to be 34.9 T for Fe0.6Co0.4 composition and has been interpreted on the basis of enhancement of Fe moments in the disordered crystal lattice. [ABSTRACT FROM AUTHOR]

ZnO and Al doped ZnO nanorods have been successfully synthesized on ITO substrate via solgel dip coating method without using any catalyst. The X-ray diffraction studies showed that the Al doped ZnO samples are of hexagonal wurtzite structure. The Al ions were successfully incorporated into the ZnO lattice. Scanning electron microscopy images reveal that the average diameter of ZnO nanorods and Al doped ZnO nanorods are ∼300 nm and ∼200 nm respectively. The energy dispersive X-ray (EDS) analysis confirmed the presence Al in the ZnO thin films. The CdS quantum dot sensitized Al doped ZnO solar cell exhibited a power conversion efficiency of 1.5%. [ABSTRACT FROM AUTHOR]

The effect of film thickness on structure, microstructure, residual stress and soft magnetic properties of Fe 65 Co 35 thin films deposited on Si(001) and MgO(001) substrates was investigated by varying film thickness from 30 to 600 nm. X-ray diffraction studies showed that the FeCo films are polycrystalline in the as-deposited condition irrespective of deposition on Si or MgO substrate. The microstructure of films consisted of spherical grains for 30 nm film thickness and columnar grains for all other film thicknesses. The grain size for the films was found to increase from 15 to 50 nm with increasing film thickness. The sputtered films also exhibited tensile residual stresses with the magnitude of stress decreasing with increasing film thickness. The Fe 65 Co 35 films deposited on both substrates also exhibited very good in-plane soft magnetic properties with a saturation magnetization 4 πM s of ~23.6–23.8 kG and coercivity of ~27–30 Oe without any under-layer only for films with thickness of 30 nm. For all other thicknesses, these films exhibited a significantly higher coercivity. The observed variations in soft magnetic properties with film thickness were explained in terms of residual stress and microstructure of the films. [ABSTRACT FROM AUTHOR]

The influence of pH and current density on the structural and magnetic behavior of soft magnetic Co-Ni-Fe alloy thin films has been studied. The effect of pH and current density on the compositional, structural, and magnetic properties of the as-obtained films was investigated by EDX (energy dispersive analysis by X-rays), XRD (X-ray diffractometer) and VSM (vibrating sample magnetometer). The EDX results revealed that at the optimized deposition conditions, nickel content was low compared with cobalt and ferrous content. X-ray diffraction patterns revealed that the deposited films have polycrystalline nature with mixed (fcc-bcc) cubic structure and small crystallite size (<20 nm). The films prepared in optimized conditions exhibit high saturation magnetization (4 πM value above 2T) and low coercivity (below 160 A/m), which may be due to the reduced crystallite size. [ABSTRACT FROM AUTHOR]

Abstract: Effects of 150MeV Ni11+ swift heavy ion (SHI) irradiation on copper ferrite nanoparticles have been studied at the fluences of 1×1011, 1×1012, 1×1013, 1×1014 and 5×1014 ions/cm2. The XRD pattern shows the irradiation fluence dependant preferential orientation. Scanning electron microscope analysis displays fine blocks of material for pristine while partial agglomeration on irradiation. Notably, a large number of holes are present at the fluence of 5×1014 ions/cm2. The magnetization measurements performed in these samples exposes that the coercivity and remanence magnetization value increases due to the magnetocrystalline anisotropy up to the fluence of 1×1013 ions/cm2. At 1×1014 ions/cm2 fluence, the induced thermal energy overcomes the magnetocrystalline anisotropy constant and causes a decrease in coercivity and remanence values. The saturation magnetization decreases up to the fluence of 1×1013 ions/cm2 and then it increases for further irradiation. The change of crystalline orientation observed from XRD, the creation of holes from SEM and the change in magnetic properties are discussed on the basis of electro-phonon coupling and it invokes the thermal spike theory. [Copyright &y& Elsevier]

Influence of Ni11+ swift heavy ion (SHI) irradiation induced modifications on structural and morphological aspects of CuFe2O4 nanoparticles have been studied. The bulk sample is synthesized using co-precipitation technique. The cubic spinel structure is identified using X-ray diffraction technique and these nanoparticles have an average grain size of about 10 nm. These materials are irradiated at various fluences of 1 × 1011, 1 × 1012, 1 × 1013, 1 × 1014, and 5 × 1014ions/cm2 using Ni11+ ion beam of 150 MeV energy. The XRD pattern of the irradiated material shows the change in crystalline nature. The spinel ferrite (311) peak, which is having maximum intensity in the pristine, decreases at the fluence of 1 × 1011 and 1 × 1012ions/cm2 and then completely vanishes on further irradiation. However, a new X-ray peak arises in the (222) direction. All the other peaks in the pristine sample vanish on irradiation elucidating the creation of amorphization nature. Scanning electron microscope (SEM) analysis shows fine blocks of material for pristine and partial agglomeration on irradiation. Notably, a large number of holes are present at the fluence of 5 × 1014ions/cm2 due to heavy ion irradiation. The phase change from crystalline to amorphous nature on XRD and the creation of holes from SEM is discussed on the basis of electrophonon coupling and it invokes the thermal spike theory. [ABSTRACT FROM AUTHOR]

In this paper we report the investigation of transition metal oxide compound, LaCaSrBaMnO (LCSBMO), along with LaCaMnO (LCMO), synthesized by sol-gel route under identical conditions. The effect of simultaneous low level substitution of large size ions such as Sr and Ba for Ca ions on the electronic transport and magnetic susceptibility properties are analysed and compared apart from microstructure and lattice parameters. The temperature dependent electrical transport of the polycrystalline pellets of LCSBMO and LCMO when obeying the well studied law, $\rho = \rho_{0} + \rho_{2} \;T^{2}$ for T < T, is observed to differ by more than 50% from the values of ρ and ρ, with the former compound showing enhanced electrical conductivity than the latter. Similarly in fitting the adiabatic small polaron model for resistivity data of both the samples for T > T, the polaron activation energy is found to differ by about 11%. In addition, the temperature dependent a.c. magnetic susceptibility study of the compounds shows a shift of about 6% in the paramagnetic to ferromagnetic transition temperature (285 K for LCSBMO and 270 K for LCMO). [ABSTRACT FROM AUTHOR]

Abstract: Cobalt–Phosphorous (Co–P) alloy thin films were prepared by electrodeposition technique from an aqueous electrolytic bath at various sodium chloride (NaCl) concentrations. The effect of sodium chloride concentration on electrochemical, structural, morphological, compositional and magnetic properties of the films was investigated by cyclic voltammetry, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and vibrating sample magnetometer techniques, respectively. The mechanism of formation of Co–P alloy thin films was studied using cyclic voltammetry. The compositional analysis shows that the content of phosphorous (P) increases and the content of cobalt (Co) decreases by adding NaCl. X-ray diffraction studies revealed amorphous nature for films obtained at high concentration of NaCl and hexagonal closed packed (hcp) structure for films obtained at low NaCl concentration. Magnetic properties illustrate that high value of coercivity, saturation magnetization, remanence, and saturating field were obtained at high concentration of NaCl. [Copyright &y& Elsevier]

Abstract: Co–Ni–P alloy thin films have been electrodeposited from sulfate baths at various solution pH and current density values. The effect of pH and current density on compositional, structural, morphological, and magnetic properties of these films was investigated by EDAX (energy dispersive analysis of X-ray spectroscopy), XRD (X-ray diffractometer system), AFM (atomic force microscope) and VSM (vibrating sample magnetometer). The reaction mechanism of individual deposition of Co, Ni and Co–Ni–P were investigated by cyclic voltammetry. The EDAX results revealed that cobalt and phosphorous content were high and nickel content was low at high solution pH and at low current density. X-ray diffraction studies exhibit that the intensity of hcp and Co–Ni–P amorphous phases increases and the intensity of fcc phase decreased when increasing the solution pH and decreasing the value of current density. The surface morphology of the films were observed by AFM. The deposited films exhibit hard magnetic properties at high pH value and soft magnetic properties at low pH value. [Copyright &y& Elsevier]

Perpendicular Magnetic Anisotropy (PMA) was realized in as-deposited Mo(10)/Co 2 FeAl 0.5 Si 0.5 (CFAS)(3)/MgO(0.5)/Mo multilayer stacks with large perpendicular magnetic anisotropy energy (K eff ). PMA of this multilayer is found to be strongly dependent on the thickness of the individual CFAS (t CFAS ), Mo (t Mo ) and MgO (t MgO ) layers and annealing temperatures. The interactions at the Mo/CFAS/MgO interfaces are critical to induce PMA and are tuned by the interfacial oxidation. The major contribution to PMA is due to iron oxide at the CFAS/MgO interface. X-ray diffraction (XRD) and infrared spectroscopic (FT-IR) studies further ascertain this. However, an adequate oxidation of MgO and the formation of (0 2 4) and (0 1 8) planes of α-Fe 2 O 3 at the optimal Mo buffer layer thickness is mainly inducing PMA in Mo/CFAS/MgO/Mo stack. Microstructural changes in the films are observed by atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) demonstrates the oxidation of CFAS/MgO interface and the formation of Fe–O bonds confirming that the real origin of PMA in Mo/CFAS/MgO is due to hybridization of Fe (3d z 2 ) and O (2p z ) orbitals and the resulted spin-orbit interaction at their interface. The half-metallic nature CFAS with Mo layer exhibiting PMA can be a potential candidate as p-MTJs electrodes for the new generation spintronic devices. [ABSTRACT FROM AUTHOR]

Compared to single-phase multiferroic materials, multiferroic (MF)-magnetoelectric (ME) composites, which combine magnetic and ferroelectric materials, show improved (many orders of magnitude) ME coupling and a higher operating temperature (beyond room temperature). In the present study, lead-free multiferroic Ni0.5Co0.5Fe2O4/BaTiO3 (NCFO/BTO) composites with different weight percentages were prepared through the solid-state reaction approach. The phase purity and structural confirmation were carried out using X-ray diffractograms. The XRD peak shifting in the composites has been observed, and it is attributed to the formation of residual stresses/strains during the sample’s grinding, heating, and freezing processes. Fourier-transformative infrared spectroscopy confirmed the presence of metal-oxygen bonds in spinel NCFO and Ti-O and Ba-O bonds in perovskite BaTiO3. UV-vis spectra disclose the energy gap values of the magnetoelectric composites. It has been found that the energy gap values for pure ferrite are 1.53 eV, the pure ferroelectric phase is 2.99 eV, and the composites possess the Eg values of 1.78 eV, 2.33 eV, 2.77 eV with decreasing ferrite concentration. The M-H hysteresis loops reveal the ferromagnetic nature of pure ferrite as well as the presence of ferromagnetism in composites. The magnetic moment of the NCFO has been found as 2.26 µB and it further decreased to 0.59 µB for the 0.25NCFO-0.75BTO compound. The magneto crystalline anisotropy has been calculated using the law of approach (LA) method and the details are discussed in the paper. [ABSTRACT FROM AUTHOR]

Abstract: Thin films of zinc oxide (ZnO) have been grown by potentiostatic cathodic deposition onto tin oxide-coated glass from a simple aqueous zinc nitrate electrolyte. Cyclic voltammetry (CV) experiments were performed to determine the reaction kinetics of the species. The various optimum deposition parameters like potential, pH and bath temperature are found to be −1.1V (SCE), 5±0.1 and 80°C, respectively. Structural characterization by X-ray diffraction indicates the formation of ZnO film with a preferred c-axis orientation and exhibits the wurtzite structure. Optical studies revealed a band gap energy 3.32eV which is characteristic of ZnO films. SEM micrographs show a compact structure with nodular appearance, which is in agreement with the reported value of ZnO and the results are discussed. [Copyright &y& Elsevier]

Nanocrystalline spinel ferrite of composition Cu 0.2 Ni 0.2 Mg 0.2 Ca 0.4 Fe 2 O 4 is synthesized by wet hydroxyl co-precipitation method in ethylene glycol as chelating agent and sodium hydroxide as precipitator at pH 8. Ethylene glycol is utilized as the medium which serves as the dissolvable and in addition a complexing specialist. The synthesized particles are annealed at various temperatures. Thermogravimetric investigation affirms that at 280 °C ethylene glycol is dissipated totally and stable phase arrangement happens over 680 °C. FTIR spectra of as synthesized and annealed at 1050 °C recorded between 400 cm −1 and 4000 cm −1 . Structural characterizations of all the samples are carried out by X-ray diffraction (XRD) technique. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) affirm that the particles are spherical and cubic shape with the crystallite size of 12 nm to 32 nm. Magnetic measurements are performed utilizing vibrating sample magnetometer at room temperature. [ABSTRACT FROM AUTHOR]

An attempt has been made to prepare nanocrystalline nickel substituted lithium ferrites, having chemical composition Li 0.5−0.5 x Ni x Fe 2.5−0.5 x O 4 (where x =0.0–1.0 with a step increment of 0.2) by a citrate-gel auto combustion method. Structural characterization of the synthesized samples was carried out by X-ray diffraction analysis (XRD) and field emission scanning electron microscopy (FESEM). Magnetic measurements were carried out using vibrating sample magnetometer (VSM) and Mossbauer spectroscopy. From these measurements it is observed that Ni 2+ substitution in lithium ferrites has strong influence on magnetic properties. Hysteresis loops indicate that the saturation magnetization values were decreased from 56 emu/gm to 28 emu/gm by increasing the Ni 2+ content in the Li–Ni ferrite samples. This signifies the fact that the lesser magnetic Ni 2+ ions are substituted for the magnetic Fe 3+ ions in the octahedral sub-lattice of the ferrites. Field Cooled (FC) and Zero Field Cooled (ZFC) magnetization measurements under an applied field of 100 Oe and 1000 Oe in the temperature range of 5–375 K were performed on two samples Li 0.1 Ni 0.8 Fe 2.1 O 4 and NiFe 2 O 4 . The magnetization as a function of an applied field 10 T was carried out at two different temperatures 5 K and 310 K. These measurements showed the blocking temperature of the two samples at around 350 K above which the materials show super-paramagnetic behavior where the coercivity and remanence magnetization are almost zero. [ABSTRACT FROM AUTHOR]

ZnO nanorods and Cu doped ZnO nanorods thin films have been prepared by simple hydrothermal method. CdS quantum dots are sensitized with Cu doped ZnO nanorod thin films using successive ionic layer adsorption and reaction (SILAR) method. The X-ray diffraction study reveals that ZnO nanorods, and CdS quantum dot sensitized Cu doped ZnO nanorods exhibit hexagonal structure. The scanning electron microscope image shows the presence of ZnO nanorods. The average diameter and length of the aligned nanorod is 300 nm and 1.5 μm respectively. The absorption spectra shows that the absorption edge of CdS quantum dot sensitized ZnO nanorod thin film is shifted toward longer wavelength region when compared to the absorption edge of ZnO nanorods film. The conversion efficiency of the CdS quantum dot sensitized Cu doped ZnO nanorod thin film solar cell is 1.5%. [ABSTRACT FROM AUTHOR]

A drop of phosphorus 'spin on dopant 430' was sprayed on ZnO pellets (prepared from 99.999% ZnO powder) and sintered in air in the temperature range of 500 to 1000°C with a step of 100°C for one hour in a programmable diffusion furnace. Characterization of asprepared ZnO pellets was performed by various diagnostic techniques: e.g., X-ray diffraction confirmed hexagonal structure of ZnO pellets preferably along (002) direction. We observed forward shift in 2 theta value of the X-ray diffraction pattern of ZnO sintered at temperature 1000°C. We correlate the forward shift with the involvement of phosphorus with vacancy at Zn site. Theoretical calculations on a 32-atoms super cell of phosphorus doped ZnO further supported the argument in the shape of a shallow acceptor PZn - 2VZn complex on Zn site. Typical PL spectra displayed band-to-band transitions peak and an additional donor-acceptor peak at ∼3.14 eV in all samples. [ABSTRACT FROM AUTHOR]

Abstract: Small crystallites of a metastable phase Co0.5Pt0.5 are precipitated by heating a rheological liquid precursor of cobalt–hydrazine complex and platinum chloride H2PtCl6·xH2O in polymer molecules of poly(vinylpyrrolidone) (PVP) in ethylene glycol. The hydrazine co-reduces nascent atoms from the Co2+ and Pt4+ that recombine and grow as Co0.5Pt0.5. The PVP molecules cap a growing Co0.5Pt0.5 as it achieves a critical size so that it stops growing further in given conditions. X-ray diffraction pattern of a recovered powder reveals a crystalline Co0.5Pt0.5 phase (average crystallite size D∼8nm) of a well-known Fm3m-fcc crystal structure with the lattice parameter a=0.3916nm (density ρ=14.09g/cm3). A more ordered L10 phase (ρ=15.91g/cm3) transforms (D≥25nm) upon annealing the powder at temperature lesser than 700°C (in vacuum). At room temperature, the virgin crystallites bear only a small saturation magnetization M s=5.54emu/g (D=8nm) of a soft magnet and it hardly grows on bigger sizes (D≤31nm) in a canted ferromagnetic structure. A rectangular hysteresis loop is markedly expanded on an optimally annealed L10 phase at 800°C for 60min, showing a surface modified coercivity H c=7.781kOe with remnant ratio M r/M s=0.5564, and M s=39.75emu/g. Crystallites self-assembled in an acicular shape tailor large H c from ideal single domains and high magnetocrystalline anisotropy of a hard magnet L10 phase. [Copyright &y& Elsevier]

Abstract: Co/Cu core/shell nanocomposites (CSNCs) with varying shell thickness were synthesized through a modified polyol process in conjunction with a transmetallation reaction. Tuning of shell thickness was achieved by subtle change in concentration of copper acetate infused in different experiments against a fixed cobalt precursor concentration. Formation of Cu nanoparticles (NPs) was observed from UV–vis spectra, which showed a typical surface plasmon resonance peak at 560nm. Precise control over particle size was obtained by the use of PVP as stabilizer, which was confirmed by a red shift of 20cm−1 in the Cing frequency of various PVP coated Co/Cu CSNCs. Powder X-ray diffraction patterns elucidate the co-existence of distinctive fundamental peaks for both Co and Cu indicating that they have not formed an alloy during the reaction. TEM images corroborate with the above result by revealing the existence of lighter shaded Cu shells coated over dark inner cores of Co. Coalescence of adjacent Cu shells gives a matrix like appearance in case of Co21.2Cu78.8 NPs; whereas Co90.7Cu9.3 NPs were distinctly separated from each other. Magnetic hysteresis loops of all the Co/Cu CSNCs showed ferromagnetic behavior and an increase in magnetization value with decrease in shell thickness was observed. [Copyright &y& Elsevier]

Abstract: Lanthanum based mixed valence manganite system La1−x Ca x−0.08Sr0.04Ba0.04MnO3 (LCSBMO; x=0.15, 0.24 and 0.33) synthesized through the sol–gel route is systematically investigated in this paper. The electronic transport and magnetic susceptibility properties are analyzed and compared, apart from the study of unit cell structure, microstructure and composition. Second order phase transition is observed in all the samples and significant difference is observed between the insulator to metal transition temperature (T MI ) and paramagnetic (PM) to ferromagnetic (FM) transition temperature (T C ). In contrast to the insulating FM behaviour usually observed in La1−x Ca x MnO3 (LCMO) for x=0.15, a clear insulator to metal transition is observed for LCSBMO for the same percentage of lanthanum. The temperature dependent resistivity of polycrystalline pellets, when obeying the well studied law ρ=ρ o +ρ 2 T 2 for TT MI . AC magnetic susceptibility study of the polycrystalline powders of the manganite system shows the highest PM to FM transition of 285K for x=0.33. [ABSTRACT FROM AUTHOR]

Abstract: With a view to understand the influence of nano size on various properties of cobalt-doped ZnO-based diluted magnetic semiconductors, a series of materials were prepared by the citrate gel route. The phase and morphology studies have been carried out by X-ray diffraction and transmission electron microscopy, respectively. All the samples of the present investigation are found to have hexagonal wurtzite structure and crystallite sizes are found to vary from 25nm to 65nm. From the optical absorption measurements it has been observed that upon doping with cobalt, the energy band gap is found to shift towards lower energy side (red shift) while it shifts towards higher energy side (blue shift) when the crystallite size is increased continuously. It has been observed from the XPS results that oxidation state of Cobalt is +2 and that the difference in binding energies of Co 2p3/2 and Co 2p1/2 is found to increase continuously with increasing crystallite size. Finally, all the samples are found to exhibit room temperature ferromagnetism and the specific magnetization decreases with increasing crystallite size. [Copyright &y& Elsevier]

Abstract: Thin films of iron diselenide (FeSe2) were electrodeposited on tin oxide coated conducting glass substrates at various bath temperatures. The deposited films were characterized by X-ray diffraction (XRD), optical, energy dispersive analysis of X-rays (EDAX) and scanning electron microscopy (SEM). The structure was found to be orthorhombic with preferential orientation along <121> plane. X-ray line profile analysis technique by the method of variance has been used to evaluate the microstructural parameters. Various microstructural parameters such as, crystallite size, rms strain, dislocation density and stacking fault probability affecting the fraction of planes with film thickness and bath temperatures were studied. The experimental observations are discussed in detail. [Copyright &y& Elsevier]