共查询到19条相似文献,搜索用时 78 毫秒
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临界电流密度(Jc)是超导薄膜、块材、带材等材料的基本性能参数,决定了超导器件及设备的性能和稳定性,简易、准确的无损Jc测量方法对超导材料特性研究及超导器件的性能保障具有重要意义。本文介绍一种基于三次谐波测量的高温超导薄膜局部临界电流密度测量方法和测量装置。研究显示,在一定幅值的初级线圈交流磁场激励下,Ⅱ型超导体会产生非线性响应,通过分析次级线圈中三次谐波分量的幅值变化,可以推算超导体的局部临界电流密度。我们搭建了一套基于此原理、适用于液氮条件的测量装置。通过对比实验,对测量的准确性进行了验证,尤其针对微弱的微纳伏量级被测信号,采取了必要的噪声抑制措施,并通过对测量数据的校正,提高了测量的准确度。实验研究显示,基于三次谐波测量的方法对于超导薄膜的临界电流密度的测量准确度较高,进行误差修正后,测量装置的误差小于10%。超导薄膜感应法测量装置的搭建十分方便,而且应用灵活,对于大面积超导薄膜的临界电流密度分布测量具有十分显著的优势。 相似文献
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本文用扫描隧道电子显微镜和原子力显微镜观察了不同实验条件一利用激光沉积技术制备的YBqa2Cu3O7-x超导薄膜的微观结构,并分析了薄膜细胞与超导电性的关系。螺旋生长结构能减少薄膜中的弱连结和在薄膜中形成磁通钉扎中心,因此使超导薄膜的临界电流密度比同类超导体材大得多。 相似文献
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利用交流磁测量测定高温超导体临界电流密度的问题 总被引:1,自引:1,他引:0
本对交流磁测量测定高温超导体的临界电流密度中的问题进行了较详细的讨论,结出了由接收信号实部与励磁电流开始发生非线线性变化的临界点来计算样品的临界电流密度的方法。并讨论了发生这一非线性变化的物理原因,同时对大面积高温超导膜均匀性测量装置中临界电流密度测量的可靠性给出了实验证据。 相似文献
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本报告了采用单线圈感应法对大面积高温超导薄膜的临界电流密度进行无损伤测定的情况。此法为研究Jc及磁通钉扎提供了新手段。我们从理论上推导了电流比常数值,并将由此算得的Jc值与传统的输运法Jc结果进行了比较,然后开展了一些讨论。 相似文献
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本采用Newton迭代法解决了无限长各向异性HTSC导线临界电流密度的自场效应,设临界电流密度平行于x轴,外场与y轴成θ角。我们给出了零外场下,临界电流密度及其自场的空间分布,计算了平均临界电流密度与θ角和外场数值的关系,发现并讨论了自场尺寸效应中的极值问题。我们的方法将可以有效地推广到其他更复杂形状和性质的样品中。 相似文献
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The temperature and size dependence of the transport critical current in Y-123 and Bi-2223 + Bi-2212 HTSC ceramic sample has been studied. It is shown that the critical current may be presented as power function of cross section area, the critical current density is homogeneous function of coordinates and a number of properties of the critical current density are reported. 相似文献
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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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We investigated the influence of surface damage on the critical current density (Jc) of MgB2 thin films via 140-keV Co-ion irradiation. The Jc(H) of the surface-damaged MgB2 films was remarkably improved in comparison with that of pristine films. The strong enhancement of Jc(H) caused by a surface damage in MgB2 films can be ascribed to additional point defects along with an atomic lattice displacement introduced through low-energy Co-ion irradiation, which is consistent with the change in the pinning mechanism, from weak collective pinning to strong plastic pinning. The irreversible magnetic field (Hirr) at 5 K for surface-damaged MgB2 films with a thickness of 850 and 1300 nm was increased by a factor of approximately 2 compared with that of a pristine film. These results show that the surface damage produced by low energy ion irradiation can serve as an effective pinning source to improve Jc(H) in a MgB2 superconductor. 相似文献
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《Current Applied Physics》2014,14(9):1277-1281
We have investigated the critical current density for MgB2 films having various crystal orientations prepared by using a hybrid physical-chemical vapor deposition system. An enhancement of the critical current density is clearly presented in MgB2 films with an a-axis or a b-axis orientation rather than a c-axis orientation. X-ray diffraction patterns reveal a suppression of c-axis orientations while a (100) orientation becomes dominant, and the surface morphology of the a-axis-oriented film shows that the orientation of the c-axis-oriented MgB2 grains parallel to the plane of the substrate. As the a-axis orientation becomes more dominant in the MgB2 films, the field performance of the critical current density clearly becomes better. These results suggest that the synthesis of MgB2 with high ab-plane orientations is one of the keys to enhancing the critical current density in MgB2. 相似文献
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T. Sueyoshi S. Yutani T. Sogo K. Yonekura A. Adachi T. Fujiyoshi F. Mitsugi T. Ikegami N. Ishikawa S. Awaji K. Watanabe 《Physica C: Superconductivity and its Applications》2010,470(20):1295-1299
We investigated the dependences of the critical current density Jc on the magnetic field angle θ in YBa2Cu3O7−δ thin films with the crossed configurations of the columnar defects (CDs). To install the crossed CDs, the films were irradiated using the high energetic Xe ions at two angles relative to the c-axis. The additional peak around the c-axis appears in the Jc(θ) for all irradiated films. In lower magnetic fields, the height of the Jc(θ) peak caused by the crossed CDs with the crossing angles θi = ±10° was higher than that for the parallel CDs. It is considered that the correlation of the flux pinning by the crossed CDs along the c-axis occurs even in the case of θi = ±25°, which was also suggested by the kink behaviors of the scaling parameters of the current–voltage characteristics near 1/3 of the matching field. In higher magnetic fields, on the other hand, the height and width of the Jc(θ) peak for the crossed CD configurations rapidly reduce with increasing the magnetic field compared to the parallel ones. In the crossed CD configurations, the dispersion in the direction of CDs would prevent the correlation of flux pinning along the c-axis in high magnetic fields, which occurs in the parallel CD configurations due to the collective pinning of flux lines including the interstitial flux lines between the directly pinned flux lines by CDs. 相似文献
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M K Malik R V Raghavan P Chaddah PK Mishra G Ravi Kumar BA Dasannacharya 《Pramana》1987,29(1):L111-L112
We report critical current measurements on sintered Y0.35Ba0.65CuOy. The sample, in the perovskite phase, shows zero resistance at 87 K. The critical current transition is seen, in zero field
and at 77 K, at a current densityJ
c of 50 A/cm2. 相似文献
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Abdelhalim Hafid Ahmed Taoufik Abella Bouaaddi Hassan Elouaddi Ahmed Tirbiyine Brahim Lmouden Mustapha Bghour Habiba El hamidi Youssef Ait Ahmed 《Chinese Journal of Physics (Taipei)》2018,56(2):754-759
In this paper, the critical current Jc(Θ) have been investigated as a function of magnetic-field angle Θ. Θ is the angle between the c-axis and the applied magnetic field direction. This investigation concerned three temperature values (60?K, 78?K and 81?K). The normalized pinning force fp versus the normalized magnetic field h was also studied (fp?=?Fp / Fpmax and h?=?H / Hmax). The Fp expression was determined based on the Kramer model.The studied sample was a single crystal of YBaCuO thin film deposited by the ablation laser method on the surface (100) of a SrTiO3 substrate.The results of this work show the existence of point core pinning of the normal centers in the low field regime and the occurrence of the flux creep in high field regime. 相似文献
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YBa2Cu3O7 + xAg?(x = 0.0, ?5.0, ?15.0 and 20 wt%) composite samples have been prepared by the solid state reaction method. The changes in structure are confirmed from the X-ray diffraction analysis and SEM measurements. The critical current density is calculated using Bean's formula from the magnetization measurement. We find that the addition of silver in YBCO enhances the critical current density (?JC) by a factor of nearly six (for 15% Ag) in comparison to pure YBCO. Enhancement of the pinning force (FP) by a factor of ten is also reported. The enhancement in ?JC is investigated over a wide range of magnetic fields. These significant changes in ?JC and FP are attributed to the presence of Ag particles as efficient artifical pinning centers in YBCO. 相似文献
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We have measured the transport critical current densityJ
cof sintered YBa2Cu3O7, in various applied fields up to 185 Oe at 77 K. We find a sharp decay ofJ
cwith magnetic field. We show that this sharp decay is consistent with the low field hysteresis results of Groveret al. We argue that the observed field dependence is not caused by intragranular weak links. 相似文献