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Approaches to improving critical current density of YBCO superconducting thick films deposited by electrophoresis

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Science China(physics,Mechanics & Astronomy) 2004年第2期47卷 165-172页

作者： ZHU Yabin1,2. ZHOU Yueliang2. LIU Zhen2. WANG Shufang2. CHEN Zhenghao2. L?Huibin2. YANG Guozhen2. XIAO Ling3. REN Hongtao3. JIAO Yulei3.& ZHENG Minghui3.1. Department of physics, College of Science, beijing Jiaotong University, beijing 100044, China 2. laboratory of optical physics, Institute of physics and center for {13. matter physics, chinese academy of sciences, beijing 100080, China 3. General Research Institute for Nonferrous Metals, beijing 100088, China Correspondence should be addressed to Zhu Yabin (email: ybzhu@***) Department of physics College of Science Beijing Jiaotong University Beijing China laboratory of optical{2. Institute of{2. and center for condensed matter{2. Chinese Academy of Sciences Beijing China General Research Institute for Nonferrous Metals Beijing China

Fabrication of YBCO superconducting thick films by electrophoresis has been widely reported. However, the value of critical current density (J c) is far from what the practical application requires. The superconducting thick films are obtained using top-seeded melt growth method with different proportional Y2.aCuO5 (Y2.1) addition. High-pressure oxygen has been used in the annealing process to improve the uniformity of the oxygen content in the superconducting thick films. When 40mol% Y2.1 powder is added to the YBa2.u3.7–5 (Y12.) powder,J c for the superconducting thick film by approaches described above reaches 7.008×103.A/cm2.(77 K, 0 T), which is greater than the value ever reported.

关键词： YBCO thick films, electrophoretic deposition, melt-textured.

An Explicit Function Expression for dc Bias and Temperature Dependence of Magnetoresistances in Magnetic Tunnel Junctions

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Journal of Materials Science & Technology 2002年第6期18卷 497-501页

作者： Xiufeng HANState Key laboratory of Magnetism, Institute of physics and{2. of {3. matter physics, chinese academy of sciences, beijing 100080, China chinese Acad Sci Inst Phys State Key Lab Magnetism Beijing 100080 Peoples R China chinese Acad Sci Ctr Condensed Matter Phys Beijing 100080 Peoples R China

An explicit function expression for the bias voltage or/and temperature dependences of tunnel magnetoresistance ratio and resistances were obtained with a unique set of intrinsic parameters. Two of these intrinsic parameters are the Curie temperature TC and the density of state (DOS) for itinerant majority and minority electrons ξ(ρM/ρm), which are the eigen parameters of ferromagnetic electrodes. Others are the spin-dependent matrix-element ratio (i.e., |Td|2.|TJ|2.) and the anisotropic-wavelength-cutoff energy ECγ of spin-wave spectrum in magnetic tunnel junction (MTJ), which are the structure parameters of an MTJ. These intrinsic parameters can be predetermined using the experimental measurement or, in principle, using the first-principle calculation method for an MTJ with the three key layers of FM/I/FM. Furthermore, a series of experimental data for an MTJ, for example, a spin-valve-type MTJ of Ta (5 nm)/Ni79Fe2.(2. nm)/lr2.Mn78(12.nm)/Co75Fe2.(4 nm)/AI(0.8 nm)-oxide/Co75Fe2.(4 nm)/Ni79Fe2.(2. nm)/Ta (5 nm) in this work, can be self-consistently evaluated and explained using such concise explicit function formulations.

关键词： Magnetic tunnel junction TMR Spin-electron transport Magnon excitation Spin-polarization Magnetotransport

The size effect on transport properties of colossal magnetoresistance materials La_(0.67)Ca_(0.3.)MnO_3

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Science China(physics,Mechanics & Astronomy) 2008年第3期51卷 251-257页

作者： LI PeiGang1,2.LEI Ming1,2.GUO YanFeng2.GUO Xi2.CHEN LeiMing2. TANG WeiHua1,2.SONG PengYun3.& CHEN JinPing3.1 Department of physics,center for Optoelectronics Materials and Devices,Zhejiang Sci-Tech University,Hangzhou 3.0018,China 2.National{2. for condensed matter physics,Institute of physics,chinese academy of sciences,beijing 100080,China 3.Department of physics,Peking University,beijing 100875,China Department of physics Center for Optoelectronics Materials and Devices Zhejiang Sci-Tech University Hangzhou China National laboratory for condensed{2. {3. Institute of Physics Chinese Academy of Sciences Beijing China Department of physics Peking University Beijing China

High quality La0.67Ca0.3.MnO3.(LCMO) film was deposited via a novel pulsed electron deposition technique on SrTiO3.100) single crystal substrate. The micro-bridge with different widths was fabricated by using electron beam lithography (EBL) technique and their transport properties were studied. For the micro-bridges with width of 2.and 1.5 μm,the insulator-to-metal transition temperature (TP) keeps un-changed compared with the film. For the micro-bridges with width of 1 μm,the TP shifts towards the lower temperature by 50 K. When the width decreases down to 500 nm,the insulator-to-metal transition disappears. The magnetoresistance be-havior of these micro-bridges was studied,and the results show that the low field magnetoresistance (LFMR) decreases and the high field magnetoresistances (HFMR) keep almost unchanged as the width of micro-bridge is reduced.

关键词： colossal magnetoresistance pulsed electron deposition electron beam lithography electrical transport properties

High-pressure synthesis and properties of CeO_2.ZrO_2.solid solution

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chinese Science Bulletin 2001年第10期46卷 801-806页

作者： XU Dapeng, WANG Quanyong, LU Zhe, LIU Zhiguo, ZHANG Gongmu & SU Wenhui1. Department of physics, Jilin University, Changchun 13.02. China 2. International {3. for Materials physics, chinese academy of sciences, Shenyang 110015, China 3. {3. for condensed matter and Radiation physics, China {3. of Advanced Science and Technology (World laboratory), beijing 100080, China Department of physics Jilin University Changchun China International center for Materials physics Chinese Academy of Sciences Shenyang China center for condensed{2. and Radiation {3. China Center of Advanced Science and Technology (World Laboratory) Beijing China

Using nanoparticles of CeO2.and ZrO2.prepared by the chemical precipitation method as starting materials, the single-phase cubic Ce0.5Zr0.5O2.solid solution (c-Ce0.5Z0.5O2. has been synthesized under 3.1 GPa at 1073.K for the first time. The structure of the c-Ce0.5Zr0.5O2.has not been changed before and after annealing at 773.K for 1 h. Only an unknown EPR signal (g =1.990) has been observed in the c-Ce0.5Zr0.5O2.and not varied after annealing at 773.K for 1 h, which exhibited that there exists no Ce3. in the c-Ce0.5Zr0.5O2.and the Ce4+ has not been reduced into Ce3. after annealing. The transport mechanism is ionic for the c-Ce0.5Zr0.5O2. The bulk conductivity (a =1.2.10-5 S/cm at 82. K, σ=2.1 ×10-3.S/cm at 112. K) is the same as that of CeO2. but smaller than that of Y2.3.stabilized ZrO2. A marked curvature at T = 82. K has been observed in the Arrhenius plot of the bulk conductivity. The activation energy below 82. K is lower than that above 82. K, and the reason has been discussed.

关键词： CeO2.ZrO2 nanocrystalline high-pressure and -temperature solid-state reaction solid solution.

Colossal magnetoresistive p-n junctions of perovskite oxide La_(0.9)Sr_(0.1)MnO_3.SrNb_(0.01)Ti_(0.99)O_3

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chinese Science Bulletin 2003年第13期48卷 1328-1330页

作者： L Huibin, DAI Souyu, CHEN Zhenghao, YAN Lei, ZHOU Yueliang & YANG Guozhen laboratory of optical{2., Institute of{2. & center for condensed matter{2., chinese academy of sciences, 100080 beijing, China laboratory of optical{2. Center for Condensed Matter Physics Chinese Academy of Sciences 100080 Beijing China

We have successfully fabricated the colossal magnetoresistive (CMR) p-n junctions of perovskite oxide La0.9Sr0.1MnO3.SrNb0.01Ti0.99O3.(LSMO/SNTO) with laser molecular beam epitaxy. The I-V characteristics of the LSMO/SNTO p-n junctions as a function of applied magnetic field (05 T) were studied between 100 and 3.0 K. We found that the p-n junction exhibited the CMR behavior. The CMR ratio rR/R0 (rR = RH - R0) is positive in magnetic fields below 0.13.T and at high temperature, while it displays a negative CMR near 100 K and in magnetic fields over 0.13.T. The CMR ratio values are 8% at 0.1 T and 13. at 5 T and 3.0 K, 40% at 0.1 T and 150 K, 10% at 0.13.T and 60% at 5 T and 100 K. The CMR behavior of the p-n junction is different from those of the LaMnO3.compound family.

关键词：巨磁电阻钙钛矿氧化物 LSMO/SNTO CMR 激光分子束外延超导体

Fluorescence dynamics of interactions between polyamide PyPyPyβDp and DNA

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Science China Chemistry 2006年第1期49卷 75-80页

作者： ZHANG Huijuan1,2. WANG Jin3. WU Yishi1, YUAN Gu3. AI Xicheng1, WANG Li4 & ZHANG Jianping1 1. State Key laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, chinese academy of sciences,{2., China 2. School of Life Science and Technology, beijing Institute of Technology, beijing 100081, China 3. College of Chemistry and Molecular Engineering, Peking University,{2., China 4. center for condensed matter physics, Institute of physics, chinese academy of sciences,{2., China Correspondence should be addressed to Ai Xicheng and Zhang Jianping State Key laboratory for Structural Chemistry of Unstable and Stable Species Institute of Chemistry Chinese Academy of Sciences Beijing China School of Life Science and Technology Beijing Institute of Technology Beijing China College of Chemistry and Molecular Engineering Peking University Beijing China center for condensed{2. {3. Institute of Physics Chinese Academy of Sciences Beijing China

The photophysical properties of the polyamide PyPyPyβDp (PPP) were investigated by means of steady-state absorption and fluorescence spectroscopies, as well as time-resolved fluo-rescence spectroscopy. It was found that the excited-state properties of PPP are very sensitive to solvents. In TKMC buffer PPP exhibited weak fluorescence with a decay time constant of 16 ps, while with the decrease of the solvent polarity PPP showed the blue-shifted peak position, increased inten-sity and lengthened life-time for its fluorescence behavior. In the presence of calf thymus DNA, it was observed that the fluorescence intensity was enhanced and the fluorescence lifetime increased from 16 to 3.0}ps for PPP, which verified that PPP bound into the minor groove of DNA duplex.

关键词： polyamide (PPP), calf thymus DNA (ctDNA), time-resolved fluorescence spectroscopy, recognition dynamics.

CeO_2.thin films grown on biaxially textured nickel(001)

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chinese Science Bulletin 1998年第20期43卷 1718-1722页

作者： WANG Rongping, XIONG Xuming, Guo Xiangxin, ZHOU Yueliang, L Huibin, PAN Shaohua, CHEN Zhenghao and YANG Guozhen laboratory of optical{2., Institute of{2. and center for condensed matter{2., chinese academy of sciences, beijing 100080, Ch laboratory of optical{2. Institute of Physics and Center for Condensed Matter Physics Chinese Academy of Sciences Beijing China

CeO\-2.films have been grown on biaxially textured Ni substrates at various temperatures. The results show that CeO\-2.films without IBAD are dominated by (111) orientation from room temperature to 800℃ while the preferential orientation of CeO\-2.films with IBAD is (001) at lower deposition temperature and (111) at deposition temperature higher than 450℃. CeO\-2.films with better in_plane texture and out_of_plane orientation can be grown at 3.0℃ with 2.0 eV ion energy and 2.0 μA/cm\+2.ion current density.

关键词： CeO\-2 films biaxial nickel.

Mechanisms of the pancake vortex and vortex line movement in the high T_c superconductors Bi_2.r_2.aCu_2._8+δ and La_(1.93.Sr0.0_7CuO_4+δ

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Science China(physics,Mechanics & Astronomy) 2007年第2期50卷 240-248页

作者： WANG WeiXian1,ZHOU Fang2.TAN Shun1,WU Huan1 & ZHANG YuHeng1 1 National High Magnetic Field laboratory,University of Science and Technology of China,Hefei 2.002.,China 2.National laboratory for Superconductivity,lnstitute of{2. and the center for condensed matter{2.,chinese academy of {13.,beijing 100080,China National High Magnetic Field laboratory University of Science and Technology of China Hefei China National laboratory for Superconductivity Institute of Physics and the Center for Condensed Matter Physics Chinese Academy of Sciences Beijing China

In the strict sense, it is not very clear why with magnetic field increasing, the normal-superconductive (NS) transition becomes broad for Bi2.r2.aCu2.8+δ(Bi2.12. while the NS transitions are almost parallel for La193.roo7Cu04+δ(La2.4). In this paper, R-T relations are measured by the six-probe method. We propose a moving mechanism of the pancake vortex and vortex line for Bi2.12. The theoretical curves fit the experiment data well.

关键词： superconductivity superconductive pancake vortex dynamics

PHASE EXTENSION AND STRUCTURE ANALYSIS BY THE MAXIMUM ENTROPY METHOD

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Acta Metallurgica Sinica(English Letters) 1998年第4期11卷 241-254页

作者： G.B.Hu and Q.B.Yang (Department of physics, Xiangtan University, Xiangtan 411105, China)(beijing{2. of Electron Microscopy, {3. for condensed matter physics, The chinese academy of sciences, P. O. Box 2.2., beijing 100080, China) Xiangtan Univ Xiangtan China

Excellent results are obtained in structure analysis with jew phases of structure factors by the maximum-entropy method (MEM) for CaGaN PbCO3.and ReBe2. single crystals. The computation time and memory space are minim... 详细信息

关键词： maximum entropy method structure analysis phase extension,symmetry