Room temperature ferromagnetism in chemically synthesized ZnO rods

We report structural and magnetic properties of pure ZnO rods using X-ray diffraction (XRD), magnetization hysteresis (M-H) loop and near edge x-ray fine structure spectroscopy (NEXAFS) study at O K edge. Sample of ZnO was prepared by co-precipitation method. XRD and selective area electron diffraction measurements infer that ZnO rods exhibit a single phase polycrystalline nature with wurtzite lattice. Field emission transmission electron microscopy, field emission scanning electron microscopy micrographs infers that ZnO have rod type microstructures with dimension 200 nm in diameter and 550 nm in length. M-H loop studies performed at room temperature display room temperature ferromagnetism in ZnO rods. NEXAFS study reflects absence of the oxygen vacancies in pure ZnO rods.Comment: 8 Pages, 3 Figure

Observational Constraints on Chaplygin Quartessence: Background Results

We derive the constraints set by several experiments on the quartessence Chaplygin model (QCM). In this scenario, a single fluid component drives the Universe from a nonrelativistic matter-dominated phase to an accelerated expansion phase behaving, first, like dark matter and in a more recent epoch like dark energy. We consider current data from SNIa experiments, statistics of gravitational lensing, FR IIb radio galaxies, and x-ray gas mass fraction in galaxy clusters. We investigate the constraints from this data set on flat Chaplygin quartessence cosmologies. The observables considered here are dependent essentially on the background geometry, and not on the specific form of the QCM fluctuations. We obtain the confidence region on the two parameters of the model from a combined analysis of all the above tests. We find that the best-fit occurs close to the $\Lambda$CDM limit ($\alpha=0$). The standard Chaplygin quartessence ($\alpha=1$) is also allowed by the data, but only at the $\sim2\sigma$ level.Comment: Replaced to match the published version, references update

Constraints on cosmological models from strong gravitational lensing systems

Strong lensing has developed into an important astrophysical tool for probing both cosmology and galaxies (their structure, formation, and evolution). Using the gravitational lensing theory and cluster mass distribution model, we try to collect a relatively complete observational data concerning the Hubble constant independent ratio between two angular diameter distances $D_{ds}/D_s$ from various large systematic gravitational lens surveys and lensing by galaxy clusters combined with X-ray observations, and check the possibility to use it in the future as complementary to other cosmological probes. On one hand, strongly gravitationally lensed quasar-galaxy systems create such a new opportunity by combining stellar kinematics (central velocity dispersion measurements) with lensing geometry (Einstein radius determination from position of images). We apply such a method to a combined gravitational lens data set including 70 data points from Sloan Lens ACS (SLACS) and Lens Structure and Dynamics survey (LSD). On the other hand, a new sample of 10 lensing galaxy clusters with redshifts ranging from 0.1 to 0.6 carefully selected from strong gravitational lensing systems with both X-ray satellite observations and optical giant luminous arcs, is also used to constrain three dark energy models ($\Lambda$CDM, constant $w$ and CPL) under a flat universe assumption. For the full sample ($n=80$) and the restricted sample ($n=46$) including 36 two-image lenses and 10 strong lensing arcs, we obtain relatively good fitting values of basic cosmological parameters, which generally agree with the results already known in the literature. This results encourages further development of this method and its use on larger samples obtained in the future.Comment: 22 pages, 5 figures, 2 tables; accepted by JCA

Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.</p

NEW WATER SOLUBLE NEGATIVE PHOTORESIST CONTAINING N-PHENYLMALEIMIDE GROUPS

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Electronic structure of Ln2O2Te (Ln=La, Sm and Gd) by X-ray absorption spectroscopy

International audienceThe oxytellurides are layered structure material which shows low lattice thermal conductivity and hence making them suitable for high temperature thermoelectric applications. We report the electronic structural properties of rare-earth doped oxytellurides [Ln2O2Te (Ln = La, Sm and Gd)] prepared by solid state reaction method. This research is focused on the suitability of rare-earth oxychalcogenide as a thermoelectric material using the electronic structure investigations. The X-ray absorption spectra at O K-edge show the O 2p bonding with Ln 5d and 4f and Te 5s states and the Ln M-edges show that the valences of Ln are to be trivalent or mixed states. The Ln M-edges are also simulated with Cowan code, and electronic structures of these oxytellurides are discussed. The substitution of different rare earth metals at the Ln-site, may enhance the thermoelectric property and stability of the material. © 2018 Elsevier Lt

Soft X-ray Absorption Spectroscopic Investigation of Li(Ni0.8Co0.1Mn0.1)O-2 Cathode Materials

Herein, we report the soft X-ray absorption spectroscopic investigation for Li(Ni0.8Co0.1Mn0.1) O-2 cathode material during charging and discharging. These measurements were carried out at the Mn L-, Co L-, and Ni L-edges during various stages of charging and discharging. Both the Mn and Co L-edge spectroscopic measurements reflect the invariance in the oxidation states of Mn and Co ions. The Ni L-edge measurements show the modification of the oxidation state of Ni ions during the charging and discharging process. These studies show that e(g) states are affected dominantly in the case of Ni ions during the charging and discharging process. The O K-edge measurements reflect modulation of metal-oxygen hybridization as envisaged from the area-ratio variation of spectral features corresponding to t(2g) and e(g) states.11Yscopu

Ferromagnetism and metal-semiconducting transition in Fe-doped ZnO thin films

We report the room temperature ferromagnetism and a metal-semiconductor transition at 227 K in 200 MeV Ag15+-ion irradiated thin films of Fe-implanted ZnO. The single phase nature of Fe-doped ZnO after ion irradiation is confirmed by x-ray diffraction. Magneto-resistance measurements show spin polarization below 150 K. X-ray absorption spectroscopy and x-ray magnetic circular dichroism studies at room temperature reveal that Fe is oxidized in a mixed valence (Fe2+ and Fe3+) state and the magnetic signal is due to the Fe2+ state. The observations are explained on the basis of the combined effect of carrier doping by Fe3+ and oxygen vacancies. © 2008 IOP Publishing Ltd

Roles of a strain relaxation and an oxygen vacancy on nanoscale inhomogeneities in VO2 thin film

We investigated structural and electronic inhomogeneities in a VO2 thin film grown on a (001)-oriented TiO2 substrate by exploiting nano-scale and macroscopic probing techniques. A compressive strain along the out-of-plane direction becomes additionally relaxed via microcracks which form a micron-sized rectangular pattern. A large inhomogeneity in the dielectric response is observed near the crack, and this signifies a strong coupling between electronic and lattice degrees of freedom. Interestingly, the strong inhomogeneity is observed also inside of the rectangular pattern, and it shows a gradient along one crystalline axis. We attribute such peculiar inhomogeneity observed in a relatively large length scale possibly to a combined effect of the strain relaxation and an oxygen vacancy distribution. As the nano-scale inhomogeneities in structural and electronic properties will eventually determine macroscopic responsivities, this work can be a good guide in designing VO2 thin films with appropriate controls of the strain and the chemical composition to realize better functionalities. © 2022FALS