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Sizable Residual Quasiparticle Density of States Induced by Impurity Scattering Effect in Ba（Fe1-xCox）2As2 Single Crystals

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Chinese Physics Letters 2010年第3期27卷 278-281页

作者：牟刚曾斌程鹏王钊胜方磊沈冰单磊任聪闻海虎 National Laboratory for superconductivity Institute of Physics and Beijing National Laboratozy for Condensed Matter Physics Chinese Academy of Sciences PO Box 603 Beijing 100190

Low-temperature specific heat Cp is measured on Ba（Fe1-xCox）2As2 single crystals in a wide doping region. A sizeable residual specific heat coefficient γo is observed in the low temperature limit of all samples. The specific heat jump near Tc, i.e. ΔCp/T／T_c, is also determined. It is found that -γo, ΔCp/T／T_c and Tc all share a similar evolution with doping. These can be well understood within the model of S± pairing symmetry when accounting for the cobalt-dopants as unitary scattering centers in the FeAs planes. Our results reveal a non-trivial impact of impurity scattering in FeAs-based.

关键词： Cold Specific heat Temperature Measurement Heat Heating Accounting Broadcasting Doping

Preparation and the physical properties of antiperovskite-type compounds Cd1_xInxNNi3（n〈x〈0.2）and Cd1-yCuyNNi3（0〈y〈0.2）

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Chinese Physics B 2012年第4期21卷 505-512页

作者：贺兵董成杨立红葛林慧慕利斌陈晓超 National Laboratory for superconductivity Institute of PhysicsChinese Academy of SciencesBeijing 100190China Luzhou Medical College Luzhou 646000China

Two series of Cdl-xInxNNi3 （0 〈 x 〈 0.2） and Cd1_yCuyNNi3 （0 〈 y 〈 0.2） samples were prepared from CdO, In203, CuO, and nickel powders under NH3 atmosphere at 773 K. The structural and physical properties were investigated by means of X-ray powder diffraction temperature-dependent resistivity and magnetic measurements. X-ray powder diffraction results showed that the Cd1-xInxNNi3 and Cd1_yCuyNNi3 compounds have a typical antiperovskite structure, and the CdNNi3, Cd0.9In0.1NNi3, and Cd0.9Cu0.1NNia compounds show metallic temperature-dependent resistivity and exhibit a Fermi liquid behavior at low temperature. In contrast to the paramagnetism previously reported, the CdNNi3 sample exhibits very soft and weak ferromagnetism, and no superconductivity was found in the Cd1-xInxNNi3 and Cdl-yCuyNNi3 samples down to 2 K. Each sample exhibited very soft and weak ferromagnetism, and the temperature dependence of the magnetization of the Cd1-xInxNNi3 and Cd1_yCuyNNi3 samples can be well fitted to the combination of a Bloch term and a Curie-Weiss term.

关键词： nitride antiperovskite weak ferromagnetism Fermi liquid

Nodal Gap in Fe-Based Layered Superconductor LaO0.9F0.1-δFeAs Probed by Specific Heat Measurements

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Chinese Physics Letters 2008年第6期25卷 2221-2224页

作者：牟刚祝熙宇方磊单磊任聪闻海虎 National Laboratory for superconductivity Institute of Physics and Beijing National Laboratory for Condensed Matter Physics Chinese Academy of Sciences PO Box 603 Beijing 100190

We report the specific heat measurements on the newly discovered Fe-based layered LaO0.9Fo0.1-δFeAs superconductor with the onset transition temperature Tc ≈ 28 K. A nonlinear magnetic field dependence of the electronic specific heat coefficient γ（ H） has been found in the low temperature limit, which is consistent with the prediction for a nodal superconductor. The maximum gap value △0 ≈ 3.4 ± 0.5 meV is derived by analysing γ（H） based on the d-wave model. We also detected the electronic specific heat difference between 9 T and 0 T in a wide temperature range, a specific heat anomaly can be clearly observed near Tc, The Debye temperature of our sample is determined to be about 315.7K. Our results suggest an unconventional mechanism for this new superconductor.

关键词： supernova explosion proto-neutron star shock wave

Superconducting Properties of MgB_(2) Prepared by High Pressure and Ambient Pressure

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Chinese Physics Letters 2001年第4期18卷 589-591页

作者：任治安车广灿赵忠贤陈红董成倪泳明贾顺莲闻海虎 National Laboratory for superconductivity Institute of Physics and Center for Condensed Matter PhysicsChinese Academy of SciencesBeijing 100080

The new superconductor MgB_(2) has been prepared by two ways: high pressure and ambient pressure synthesis. Their superconducting properties were measured and compared. It is found that the sample prepared by high pressure is much denser than that prepared under ambient pressure. Accordingly the high pressure sample has a very narrow transition width and a much higher bulk critical current density.

关键词： synthesis. ambient superconductor

Microstructure and superconducting properties of (BaTiO3,Y2O3)-doped YBCO films under different firing temperatures

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Rare Metals 2017年第1期36卷 37-41页

作者： Hong-Yan Wang Fa-Zhu Ding Hong-Wei Gu Hui-Liang Zhang Ze-Bin Dong University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Applied superconductivity Institute of Electrical Engineering Chinese Academy of SciencesBeijing 100190 China

YBaCuO(YBCO) films with co-doping of Ba Ti O(BTO) and YOnanostructures were successfully fabricated on La Al O(LAO) substrate by metal organic deposition using trifluoroacetates(TFA-MOD). The focus of this study was to optimize the process conditions during the firing heat treatment of high critical current density(J C)-co-doped YBCO films. The effect of the firing temperatures on both the surface morphology and the superconducting properties for the doped YBCO films was systematically studied. According to the X-ray diffraction(XRD) and scanning electron microscopy(SEM) results,the films prepared at 820 and 850 °C show poor electrical performance due to impurity phases and large pores. In contrast, the dense YBCO films prepared at 830 and840 °C with the critical current densities of 10 MA-cm(77 K, 0 T) are obtained.

关键词： YBa2Cu3O7-x BaTiO3 and Y2O3 nanostructures Firing temperature TFA-MOD

Observation of lateral long range order in superconducting FeTe thin films

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Chinese Physics B 2010年第8期19卷 18-23页

作者：李位勇韩烨王焕华曹立新贾全杰陈雨姜晓明董成许波赵柏儒 National Laboratory for superconductivity Institute of Physics and Beijing National Laboratory for Condensed Matter PhysicsChinese Academy of Sciences Institute of High Energy Physics Chinese Academy of Sciences

We find that the superconductivity in the thin films of the formerly believed non-superconducting parent compound FeTe is accompanied by an emergence of second order with a correlation length of 742 nm and 258 nm at 10 K and 300 K, respectively. The structural phase transition found in iron pnictide superconductors, in non-superconducting FeTe bulk samples, and in FeSe superconducting thin films is not observed in the superconducting FeTe thin films. The interplay between superconductivity and long range order may suggest the crucial role of competition between electronic localization and itinerancy which leads to strong quantum fluctuations in the FeTe system.

关键词： superconducting materials surface phase transitions and critical phenomena superconducting films x-ray determination of structures

High Temperature superconductivity in the Past Twenty Years Part 1——Discovery, Material, and Theory

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Journal of Electronic Science and Technology of China 2008年第2期6卷 225-236页

作者： Jian-Xun Jin The Center of Applied superconductivity and Electrical Engineering University of Electronic Science and Technology of China Chengdu 610054 China

Twenty years after the discovery of hightemperature superconductors （HTSs）, the HTS materials now have been well developed. Meanwhile the mechanism of superconductivity is still one of the topical interests in physics. The achievements made on HTS materials and theories during the last twenty years are reviewed comprehensively in this paper.

关键词： High temperature superconductivity,high temperature superconductor high temperaturesuperconducting theory

Asymmetric exchange bias training effect in spin glass(FeAu)/FeNi bilayers

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Chinese Physics B 2014年第10期23卷 513-518页

作者：芮文彬何茂诚游彪时钟周仕明肖明文高远张维孙力杜军 National Laboratory of Solid State Microstructures and Department of Physics Nanjing University Department of Physics Tongji University Department of Mechanical Engineering and Texas Center for superconductivity (TcSUH) University of Houston

A significant exchange bias （EB） traimng ettect has been observea in sputter deposited FeAu/FeNi bilayers, wherein the exchange field （HE） exhibits a special sign-changeable temperature dependence. Very interestingly, despite the absence of multiple easy axes in the FeAu spin glass （SG） layer, HE drops abruptly between the first and second magnetic cycles, which is followed by a more gradual continuous change in the subsequent cycles. This training behavior cannot be described by the empirical n-1/2 law because of the asymmetric magnetization reversal processes. We propose modifying Binek＇s model to include the asymmetric changes of the pinning SG spins at the descending and ascending branches. This new model successfully describes the EB training effect in FeAu/FeNi bilayers.

关键词： exchange bias training effect spin glass

A comparative study of YBa_2Cu_3O_(7-δ)/YSZ bilayer films deposited on silicon-on-insulator substrates with and without HF pretreatment

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Chinese Physics B 2009年第4期18卷 1679-1683页

作者：王萍李洁陈莺飞李绍王佳解廷月郑东宁 School of Physics and Electronics Science Shanxi Datong University National Laboratory for superconductivity Institute of Physics & Beijing National Laboratory for Condensed Matter Physics Chinese Academy of Sciences

Highly epitaxial YBa2Cu3O7-δ （YBCO） and yttria-stabilized zirconia （YSZ） bilayer thin films have been deposited on silicon-on-insulator （SOI） substrates by using in situ pulsed laser deposition （PLD） technique. In the experiment, the native amorphous SiO2 layers on some of the SOI substrates are removed by dipping them in a 10% HF solution for 15 s. Comparing several qualities of films grown on substrates with or without HF pretreatment, such as thin film crystallinity, general surface roughness, temperature dependence of resistance, surface morphology, as well as average crack spacing and crack width, naturally leads to the conclusion that preserving the native SiO2 layer on the surface of the SOI substrate can not only simplify the experimental process but can also achieve fairly high quality YSZ and YBCO thin films.

关键词： pulsed laser deposition thin film pretreatment SOI substrate