共查询到20条相似文献,搜索用时 15 毫秒
1.
利用文献所导出的补偿方程和电流方程,计算了一个载有电流的超导膜的能隙,给出了它和电流的依赖关系。所得到的结果适用于所有的温度,但电流数值要比较小。在温度接近Tc的范围内,本文还对超导膜的临界电流问题进行了讨论。文中指出,非局域效应对于比较厚的超导膜的临界电流是重要的,但是对于比较薄的超导膜是不重要的。 相似文献
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高温超导薄膜无源微波器件的应用 总被引:4,自引:0,他引:4
高温超导薄膜在微波器件中的应用,与常规导体相比可以减小器件的体积,重量,功率消耗和插入损耗,并且可以在液氮沸点附近工作,接近于卫星的环境温度100K,微波器件是在几个平方厘米的高温超导薄膜上制备的。这些薄膜必须要有最高的超导性能,如临界温度,临界电流密度以及微波表面电阻,因此高温度超导薄膜的应用受到制备大面积,高质量薄膜的限制,美国高温超导空间实验在1999年5月已经获得成功,使高温超导薄膜在微波器件中的应用成为现实。 相似文献
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L. Alff G.M. Fischer R. Gross F. Kober A. Beck K.D. Husemann T. Nissel F. Schmidl C. Burckhardt 《Physica C: Superconductivity and its Applications》1992,200(3-4):277-286
Patterning of thin films and multilevel structures of high-temperature superconductors is a key technology for microelectronic applications. We performed a comparative study of Ion Beam Etching (IBE) and Reactive Ion Etching (RIE) processes for YBa2Cu3O7−δ thin films. The RIE process with a pure chlorine plasma yielded small etching rates, caused by chemical modifications of the sample surface which result in a passivation layer reducing the chemical etching rate. Using IBE, microstructures down to the 1 μm regime could be fabricated without reducing the critical temperature Tc and the critical current density Jc of the material. Etching rates up to 40 nm/min could be achieved without deteriorating the properties of the superconducting film by cooling the sample effectively during the etching process. The influence of the etching process on Jc was investigated by imaging the spatial distribution of the critical current along the patterned microstructures using Low-Temperature Scanning Electron Microscopy (LTSEM). 相似文献
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G. N. Mikhailova E. I. Demikhov V. P. Aksenov L. Kh. Antonova L. D. Iskhakova L. N. Zherikhina E. A. Kostrov S. V. Lavrishchev V. S. Mikhailov A. V. Troitskii A. M. Tskhovrebov 《Technical Physics》2009,54(2):235-238
The stability of critical parameters T c and I c of commercial high-temperature superconducting wires upon long-term passage of transport current (about 0.7I c) in liquid nitrogen (77 K) is studied. Voltage-current characteristics U(I), as well as the critical current and critical temperature, are investigated for the case of Bi(2223) hermetic multifilament wires and Dy(123) superconducting tapes covered by a thin Ag layer. In the former case, a considerable decrease in the critical current (by ~30%) and swelling of the wires after passage of the current for 323 h are observed. The same is true for a reference sample, which does not experience the action of current and stays in liquid nitrogen for 700 h. The decrease in the critical current in the Bi(2223) sample is likely to be associated with penetration of a liquid coolant into the composite conductor: evaporating and expanding as a result of heating, it severely deforms the material. The Dy(123) sample grown epitaxially demonstrates high stability of the critical current after it has experienced the action of current for 400 h and been kept in liquid nitrogen for 1000 h. 相似文献
6.
Abdalla A. Elabbar 《Physica C: Superconductivity and its Applications》2009,469(4):147-150
Low-field ac measurements of magnetic susceptibility of YBa2Cu3O7 high-temperature superconducting thin film were carried out over a wide range of temperatures and ac magnetic field amplitudes. A strong field dependence of the real χ′ and imaginary χ″ components was observed. The field dependence of the imaginary component is used to extract the temperature dependence of the critical current density in the sample using the critical state model. The exponent β of the power law relation Jc ~ (1 ? T/Tc)β was determined from ac-susceptibility data and different values were found. Experimental results are compared with predictions of some existing theoretical models describing the ac response of superconducting thin film in perpendicular ac field. 相似文献
7.
The effect of electron-beam irradiation on the magnetic properties of (Ga1−xMnx)As thin films grown on GaAs (100) substrates by using molecular beam epitaxy was investigated. The ferromagnetic transition temperature (Tc) of the annealed (Ga0.933Mn0.067)As thin films was 160 K. The Tc value for the as-grown (Ga0.933Mn0.067)As thin films drastically decreased with increasing electron-beam current. This significant decrease in the Tc value due to electron-beam irradiation originated from the transformation of Mn substituted atoms, which contributed to the ferromagnetism, into Mn interstitials or Mn-related clusters. These results indicate that the magnetic properties of (Ga1−xMnx)As thin films grown on GaAs (100) substrates are significantly affected by electron-beam irradiation. 相似文献
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《Current Applied Physics》2019,19(12):1338-1342
CeCoIn5 (Co115) thin films have been grown on Al2O3 (000l) substrates through the pulsed laser deposition (PLD). The films are grown mainly along the c-axis, with CeIn3 and In-related alloys. The rock-salt type grains are nucleated, where Co115 grains mixed with excess indium are evenly distributed over the substrate. The electrical resistivity of the films shows a Kondo coherence peak near 47 K and the zero-resistance superconducting state at 1.8 K, which is the first observation in the PLD grown thin films of Co115. The Rietveld refinement of the thin films shows that the c/a ratio (tetragonality) is suppressed to 1.6312 from 1.6374 of single crystals, which is consistent with the linear relationship between the superconducting transition temperature and tetragonality. The good agreement indicates that the PLD could provide an alternative route to tune the 2D character of the critical spin fluctuations to understand the superconducting pairing mechanism of Co115. 相似文献
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《Current Applied Physics》2018,18(6):762-766
We report a facile method to enhance the critical current density (Jc) of superconducting MgB2 thin films. MgB2 thin films were deposited on zinc acetate dehydrate (Zn(CH3COO)22H2O) spin-coated Al2O3 (000l) substrates by using a hybrid physical-chemical vapor deposition system at low temperatures. Synthesis of MgB2 at low temperatures can reduce the substitution of Zn into the Mg site, hence avoiding the reduction of superconducting critical temperature. MgB2 thin films grown on ZnO-buffered layers showed a significant enhancement of Jc in the magnetic field due to the creation of additional pinning sources, namely point defects and grain boundaries. Broad peaks were observed in the magnetic field dependence of the flux pinning force density, indicating competition of different pinning sources. 相似文献
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利用我们设计的一套光学变换传输系统实现了激光束在超导靶上一定范围内扫描消融来淀积高Tc超导薄膜。实验表明用这种激光扫描消融方法可使大尺寸超导薄膜的厚度均匀性得到较大的改善。我们采用激光扫描半径为9mm在12mm×33mm的Y-ZrO2基片上淀积出零电阻温度Tc≥90K,临界电流密度Jc(零磁场,77K)≥1×106A/cm2,薄膜c轴择优取向,厚度均匀性较好的YBa
关键词: 相似文献
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使用外延YBa2Cu3O7薄膜,测量了低温下(液氮或液氦温度)质子辐照对样品输运性质的影响。不仅观察到由低温辐照引起的样品超导转变温度Tc下降及电阻率P上升,还观察到dp/dT的上升和发生金属至非金属的相变。经室温热循环的样品显示出强烈室温退火效应。近60%由辐照引起的样品电阻升高和Tc下降可以得到恢复,并可伴随发生非金属至金属的相变,在La-Sr-Cu-O薄膜的低温辐照实验中观察到了类似的室温退
关键词: 相似文献
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K. N. Yugai G. M. Seropyan A. A. Skutin K. K. Yugai A. B. Murav’ev 《Technical Physics》1998,43(2):176-179
The superconducting parameters and macrostructure of YBaCuO thin films grown by laser ablation on SrTiO3 substrates are influenced by the substrate temperature during growth. In a study of this influence it is found that the macrostructure
has significant bearing on the superconducting parameters of the films and on the critical current, in particular. For J
c⩽105 A/cm2 the films have a distinctly pronounced granular structure, while for J
c>105 A/cm2 the films do not have any kind of block structure.
Zh. Tekh. Fiz. 68, 48–51 (February 1998) 相似文献
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本文指出虽然三十年来Ginzberg-Landau理论(以下简称G-理论)被人们广泛地用于描述超导薄膜的临界场,而且它还是描述强耦合超导薄膜临界场的唯一理论,但G-L关于薄膜临界场的理论不仅一直未得到实验证明,而且它既不能用于描述结晶态的弱耦合超导薄膜的临界场,也不适用于描述强耦合超导薄膜的临界场。本文还提出了一个在薄膜极限下定域的新判据:ξ<<λ,ξ<关键词: 相似文献
16.
A new model analysis of the third harmonic voltage in inductive measurement for critical current density of superconducting films 下载免费PDF全文
The critical current density J c is one of the most important parameters of high temperature superconducting films in superconducting applications,such as superconducting filter and superconducting Josephson devices.This paper presents a new model to describe inhomogeneous current distribution throughout the thickness of superconducting films applying magnetic field by solving the differential equation derived from Maxwell equation and the second London equation.Using this model,it accurately calculates the inductive third-harmonic voltage when the film applying magnetic field with the inductive measurement for J c.The theoretic curve is consistent with the experimental results about measuring superconducting film,especially when the third-harmonic voltage just exceeds zero.The J c value of superconducting films determined by the inductive method is also compared with results measured by four-probe transport method.The agreements between inductive method and transport method are very good. 相似文献
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In this paper, we study the magnetic structure of the half-ring flux line ended on the surface of a superconductor. The elemental modes for these half-ring flux lines are the half-ellipse flux lines ended on and perpendicular to the surface. The statistics of these half-ring flux lines is, in a certain degree, similar to the vortex-antivortex pairs in thin superconducting films. An abrupt change of the thermodynamic properties for this system takes place at a temperature lower than Tc. It is analogous to the KT transition in thin superconducting films in certain sense. 相似文献
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The magnetic field and temperature dependence of the resistance of thin Al films have been investigated at T > Tc (Tc - superconducting transition temperature). The results are explained on the basis of localization and electron-electron interaction theory in two-dimensional disordered systems. The temperature dependence of inelastic scattering time and interaction constant for such films is found. 相似文献
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N. B. Brookes G. Ghiringhelli J. C. Cezar G. M. De Luca M. Salluzzo 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(2):153-156
X-ray absorption spectroscopy in the presence of an electric field has been used to study the doping mechanism of the CuO2 planes in Nd1+xBa2-xCu3O7 compounds. The electric field effect doping is well-known as a method to modify the electrical properties of a thin film
using an external gate voltage and in the copper based high critical temperature superconductors (HTS), it has been used to
shift the critical temperature and even to induce phase transitions. Field effect experiments in ultra-thin HTS are usually
interpreted by supposing that the induced charges develop into carriers in the CuO2 conducting planes, thus changing the filling of the Zhang-Rice (ZR) band. Here we show that the polarization charges in both
insulating and superconducting films, are mainly confined in the charge reservoir, and in particular in the CuO chains. The
characteristics of the charge reservoir layer determine the doping of the CuO2 planes, achieved by transfer of a fraction of the total injected charges. Moreover we found that holes injection in the CuO2 planes is reduced in oxygen deficient NdBCO films. 相似文献