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Absence of ferromagnetism in bulk polycrystalline Zn0.9Co0.1O

Physical Review B 2006年第22期73卷 224408-224408页

作者： S. Yin M. X. Xu L. Yang J. F. Liu H. Rösner H. Hahn H. Gleiter D. Schild S. Doyle T. Liu T. D. Hu E. Takayama-Muromachi J. Z. Jiang Laboratory of New-Structured Materials Department of Materials Science and Engineering Zhejiang University Hangzhou 310027 People's Republic of China New Materials Group Superconducting Materials Center National Institute for Materials Science 1-1 Namiki Tsukuba Ibaraki 305-0044 Japan Institute for Nanotechnology Forschungszentrum Karlsruhe P.O. Box 3640 76021 Karlsruhe Germany Institute for Nuclear Waste Disposal Forschungszentrum Karlsruhe P.O. Box 3640 76021 Karlsruhe Germany Institute for Solid State Physics Forschungszentrum Karlsruhe P.O. Box 3640 76021 Karlsruhe Germany Institute of High Energy Physics Chinese Academy of Sciences Beijing 100039 People's Republic of China

The atomic structure and the magnetic properties of 5 and 10at.% Co-doped ZnO samples prepared by a high-pressure and high-temperature method have been investigated by various techniques, including x-ray diffraction with Rietveld refinements, scanning electron microscopy, high-resolution transmission electron microscopy, nanometer-sized element mapping, x-ray photoelectron spectroscopy, near-edge x-ray absorption fine structure, and extended x-ray absorption fine structure and magnetization measurements. It is found that Co ions with a valence of 2+ substitute Zn ions in the wurtzite ZnO structure. No metallic or oxidic Co-rich clusters were detected in the samples. If Co2+ ions substitute Zn2+ ions, no intrinsic ferromagnetism is observed in ZnO at doping levels up to 10at.% Co even down to 5K. A paramagnetic behavior with partially antiferromagnetic interactions is observed. Thus, in bulk Co-doped ZnO system any observation of ferromagnetism is probably due to small clusters of second phase materials. However, in thin films the situation might be more complex, since other extrinsic influences, such as strain or proximity effects, may modify the electronic and magnetic properties.

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Size and shape of three-dimensional Cu clusters on a MgO(001) substrate: Combined ab initio and thermodynamic approach

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Physical Review B 2006年第11期74卷 115418-115418页

作者： David Fuks Eugene A. Kotomin Yuri F. Zhukovskii A. Marshall Stoneham Materials Engineering Department Ben-Gurion University of the Negev P. O. Box 653 Beer-Sheva Israel Institute for Solid State Physics University of Latvia Kengaraga 8 LV-1063 Riga Latvia Max-Planck-Institut FKF Heisenbergstr. 1 D-70569 Stuttgart Germany Center for Materials Science Department of Physics and Astronomy University College London Gower Street London WC1E 6BT United Kingdom

In order to describe theoretically metallic island growth at the early stages of metal deposition on oxide substrates, we combined ab initio atomic and electronic structure calculations with thermodynamic theory of solid solutions. The experimentally observed truncated pyramidal shape of metallic clusters is reproduced as the result of metal atom segregation from the lattice gas in imaginary Ising lattice towards the metal/substrate interface. Our approach is illustrated by detailed analysis of Cu islands on a MgO(001)-terminated surface. We predict dependencies of the shape and the height of such clusters on the temperature and metal gas pressure.

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Anomalous Electronic Raman Scattering in NaxCoO2·yH2O

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Physical Review Letters 2006年第16期96卷 167204-167204页

作者： P. Lemmens K. Y. Choi V. Gnezdilov E. Ya. Sherman D. P. Chen C. T. Lin F. C. Chou B. Keimer Max Planck Institute for Solid State Research D-70569 Stuttgart Germany Institute for Condensed Matter Physics TU Braunschweig D-38106 Braunschweig Germany 2. Physikalisches Institute RWTH Aachen D-52056 Aachen Germany Institute for Materials Research Tohoku University Sendai 980-8577 Japan B. I. Verkin Institute for Low Temperature Physics NASU 61164 Kharkov Ukraine Department of Physics University of Toronto Toronto Ontario M5S 1A7 Canada Center for Materials Science and Engineering MIT Cambridge Massachusetts 02139 USA

Raman scattering experiments on NaxCoO2·yH2O single crystals show a broad electronic continuum with a pronounced peak around 100 cm−1 and a cutoff at approximately 560 cm−1 over a wide range of doping levels. The electronic Raman spectra in superconducting and nonsuperconducting samples are similar at room temperature, but evolve in markedly different ways with decreasing temperature. For superconducting samples, the low-energy spectral weight is depleted upon cooling below T*∼150 K, indicating the opening of a pseudogap that is not present in nonsuperconducting materials. Weak additional phonon modes observed below T* suggest that the pseudogap is associated with charge ordering.

关键词： Single crystals

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The behavior of CoSn and Coln2 intermetallic compounds upon mechanical milling

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Journal of Metastable and Nanocrystalline materials 2005年 24-25卷 189-192页

作者： Kwon, Y.S. Choi, P.P. Gerasimov, K.B. Regional Research Center ReMM School of Materials Science and Engineering University of Ulsan Ulsan 680-749 Korea Republic of Institute of Solid State Chemistry and Mechanochemistry Kutateladze 18 Novosibirsk- 128 630128 Russia

To formulate a predictive model of mechanical alloying (MA) it is necessary to understand what phases are stable upon milling and can be obtained as a single-phase homogeneous product and what phases are unstable and can be obtained only as heterogeneous blends. All intermetallics, which decompose under mechanical milling (MM), are incongruently melting compounds. Thus, their mechanically driven decomposition can be attributed to local melting under ball collisions. In the present work MM of CoSn and CoIn2 intermetallics, which have peritectic melting points, have been studied. Under MM the CoSn phase decompose into the hightemperature polymorph of Co3Sn2 and solution of cobalt in tin, whereas no evidence of the decomposition of CoIn2 is found from XRD and magnetization measurements of milled samples. These results can be attributed to volume changes occurring with the decomposition. Decomposition of CoSn into Co3Sn2 and solution of iron in tin results in a negative volume change, and high local stresses under ball collisions make the decomposition favorable. In contrast, a volume change occurring with the decomposition of CoIn2 into Co and CoIn3 or solution of cobalt in indium would be positive and is thus prevented by stresses under ball collisions.

关键词： Cobalt alloys

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Depression of the peritectic melting point of FeSn2 in FeSn 2-FeSn nanocomposites produced by mechanical milling

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Journal of Metastable and Nanocrystalline materials 2005年 24-25卷 443-446页

作者： Kwon, Young-Soon Kim, Ji-Soon Gerasimov, K.B. Avramchuck, S.S. Regional Research Center ReMM School of Materials science and Engineering University of Ulsan Ulsan 680-749 Korea Republic of Institute of Solid State Chemistry and Mechanochemistry Kutateladze 18 Novosibirsk-128 630128 Russia

The particle size effect on the peritectic melting of FeSn2 particles in FeSn-FeSn2 nanocomposites was studied using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). FeSn - 10 wt.% FeSn2 compounds mechanically milled for 30 min exhibit in DSC curves a considerable decrease in the incongruent melting point from an equilibrium value of 786 K to approximately 680 K. Although FeSn2 grains grow from 10 to 40 nm upon heating in DSC before peritectic melting sets in, the melting temperature is reduced substantially. Small latent heat during peritectic melting and large interfacial energy of FeSn-FeSn2 nanocomposites are held responsible for the large particle size effect on incongruent melting. For rapid local heating under ball collisions during MM grain growth is hardly possible and therefore, a reduction in the peritectic melting temperature should be even substantially larger. Therefore, it can be concluded that local incongruent melting under ball collisions is the mechanism which underlies the mechanically driven decomposition of intermetallics.

关键词： Mechanical alloying

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Developing an atomic-level understanding of the mechanisms that govern CO2 sequestration mineral carbonation reaction processes

Developing an atomic-level understanding of the mechanisms t...

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2005 TMS Annual Meeting

作者： McKelvy, Michael J. Chizmeshya, Andrew V. G. Diefenbacher, Jason Béarat, Hamdallah Carpenter, R.W. Wolf, George Gormley, Deirdre Center for Solid State Science Arizona State University Tempe AZ 85287 United States Science and Engineering of Materials Graduate Program Arizona State University Tempe AZ 85287 United States Department of Chemistry and Biochemistry Arizona State University Tempe AZ 85287 United States

Mineral carbonation is an emerging CO2 sequestration candidate technology, which produces environmentally benign and geologically stable materials. The primary challenge is economically viable process development. Serpentine and olivine minerals are candidate feedstock materials of interest, due to their wide availability, low-cost, and rapid mineral carbonation potential. Cost-effectively enhancing their carbonation reactivity is critical to reducing mineral sequestration process cost. We will discuss our recent research into the mechanisms that govern serpentine and olivine mineral carbonation reaction processes, including in situ observations of the mineral carbonation process and a novel mechanistic approach to enhance carbonation reactivity that avoids the cost of mineral activation. Our goal is to develop the necessary atomic-level understanding to engineer improved carbonation materials and processes to reduce process cost.

关键词： Chemical reactions

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Evaluation of Ph precursors for liquid injection atomic layer deposition of Pb(ZrxTii.x)O3 thin films

Evaluation of Ph precursors for liquid injection atomic laye...

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2005 MRS Fall Meeting

作者： Watanabe, Takayuki Hoffmann-Eifert, Susanne Hwang, Cheol Seong Wase, Rainer Institute of Solid State Research CNI - Center of Nanoelectronic Systems for Information Technology Research Center Juelich Juelich D-52428 Germany School of Materials Science and Engineering Seoul National University Seoul 151 - 742 Korea Republic of

ISBN: (纸本)155899856X

Pbi(DPM)2 and Pb(TMOD)2: dissolved in ethylcyclohexane were evaluated as precursors for future atomic layer deposition (ALD) of Pb(Zr,Ti)O3 films. PbO films were deposited by a liquid injection atomic layer deposition on Pt-covered Si substrates at different deposition temperature and precursor volume per cycle. Pb(DPM)2: and Pb(TMOD)2 started thermal decomposition at deposition temperature of around 270°C and 320°C, respectively. Against increasing Pb(DPM) 2 injection at 240°C, the deposition rate of PbO films saturated at around 1 A/cycle, but kept increasiiig at 300°C, which is. above the thermal decomposition temperature. The deposition rate of PbO films at 240°C dropped to a constant value with enough purge time after precursor injection and reactant supply. A saturated deposition rate of PbO films was also observed for Pb(TMC)D)2 below the thermal decomposition temperature. However, the saturation behavior observed for Pb(TMOD)2 was slower and the saturated growth rate was higher comparing to Pb(DPM)j. In addition, the film thickness of the PbO films had an apparent gradient over the substrates. These results indicate that Pb(DPM)2 shows more reactive and stable chemisorption comparing to Pb(TMOD)2 for the self-limiting growth rate. © 2006 materials Research Society.

关键词： Thin films

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VLSI architecture design for a fast parallel label assignment in binary image

VLSI architecture design for a fast parallel label assignmen...

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IEEE International Symposium on Circuits and Systems 2005, ISCAS 2005

作者： Yang, Shyue-Wen Sheu, Ming-Hwa Wu, Hsien-Huang Chien, Hung-En Weng, Ping-Kuo Wu, Ying-Yih Graduate School of Engineering Science and Technology National Yunlin University of Science and Technology 123 Section 3 University Road Touliu Yunlin Taiwan Chung-Shan Institute of Science and Technology Materials RD Center Solid-State Devices Materials Section P.O. Box 90008-8-7 Lung-Tan Tao-Yuan 325 Taiwan

ISBN: (纸本)9780780388345

In this paper, we propose a new connected component labeling method based on a 34 window for a binary image. This method possesses parallel processing to achieve high speed operation. According to the proposed method, we design an efficient VLSI architecture which only uses two process elements and a class storage array to complete the whole label assignment after two raster scans. From experimental results, our design has better performance interms of hardware cost and speed. This architecture has been verified on FPGA. It takes 6120 logic elements and its working frequency is about 80 MHz. © 2005 IEEE.

关键词： Binary images

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Magnetization reversal of circular nanoscale ferromagnetic elements with modified shapes

Magnetization reversal of circular nanoscale ferromagnetic e...

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INTERMAG ASIA 2005: Digests of the IEEE International Magnetics Conference

作者： Hu, H. Wang, H. McCartney, M.R. Smith, David J. Dept. of Physics and Astronomy Arizona State University Tempe AZ 85287-1504 United States Dept. of Chemical and Materials Engineering Arizona State University Tempe AZ 85287-6006 United States Center for Solid State Science Arizona State University Tempe AZ 85287-1704 United States

No abstract available

ISBN: (纸本)0780390091

No abstract available

关键词： Off-axis electron holography Switching behavior Switching field Vortex

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Change detection by thresholding-with-hysteresis

Change detection by thresholding-with-hysteresis

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Seventh IASTED International Conference on Signal and Image Processing, SIP 2005

作者： Wu, Hsien-Huang P. Hsien, Jen-Chien Weng, Ping-Kuo Wu, Ying-Yih Department of Electrical Engineering National Yunlin Univ. of Sci. and Tech. #123 University Rd. Yunlin Douliu 640 Taiwan Materials RD Center Solid-State Devices Materials Section Chung-Shan Institute of Science and Technology P.O. Box 90008-8-7 Lung-Tan Yao-Yuan 325 Taiwan

ISBN: (纸本)0889865183

Moving object segmentation by change detection has been a very important topic for various video applications. Change detection can be implemented by thresholding a difference image between the current frame and a reference frame. In this paper, a novel method of thresholding for moving object segmentation is proposed without using expensive adaptive background modeling. This new approach adopts the concept of thresholding-withhysteresis and utilizes a multi-resolution/variable thresholding (MRVT) scheme to achieve improvements on the segmentation performance. Combined with simple background modeling, the proposed method can achieve accurate moving object segmentation. Simulation results are evaluated qualitatively and quantitatively to show the effectiveness of this new thresholding scheme.

关键词： Object recognition

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