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  • 1
    Electronic Resource
    Electronic Resource
    Paramagnetism and scaling behavior of volume flux pinning force density in a GdBa2Cu3O6+x thin film (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3287-3292 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic measurements have been performed on a GdBa2Cu3O6+x superconducting thin film. The paramagnetism carried by rare earth Gd3+ ions in the film tilts the magnetic hysteresis loop and broadens the width of the magnetic hysteresis ΔM, then the magnetization critical current density and the volume flux pinning force density based on the Bean critical state model deviate from intrinsic values. Therefore, in order to get useful information on the pinning mechanism, correction for the paramagnetism is essential. And after correction for the paramagnetism, a scaling law of the volume flux pinning force density is obtained as f(b)=(b/4)0.5(1−b/4)1.5, based on which the possible pinning mechanism in the film is discussed. In the end, deviation from the scaling law at high fields is interpreted by the collective pinning theory. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360019
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetization relaxation in YBa2Cu3O7−δ (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1671-1675 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The time and field sweep rate dependencies of magnetization in high temperature superconductors are derived from a combined view based on the thermally activated flux creep. The τ0 in the magnetization relaxation expression M=M0+M1 ln(1+t/τ0) is a macroscopic quantity related primarily to the sample geometry and other experimental conditions via the effective activation energy U(J0). This activation energy provides an alternative interpretation to the nearly inverse proportionality of τ0 to the field sweep rate. The values of τ0 in the magnetization relaxation of single crystal YBa2Cu3O7−δ are consistent with the calculated ones. As the nonlinear U(J) is taken into account, the curvature in the ||M||-ln t plot may change from negative to positive over a sufficiently long time window, and the magnetization hysteresis M(H) depends on the field sweep rate H(overdot) by const+A ln H(overdot)+B ln2 H(overdot), where A is slightly larger than M1 and B(approximately-greater-than)0. A discussion of the temperature dependency of the normalized flux creep rate is at the conclusion of the article.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356352
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  • 3
    Electronic Resource
    Electronic Resource
    Study of magnetization relaxation on zone-melted YBa2Cu3O6+x superconductors (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2618-2624 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The analytical magnetization versus time expressions for several flux-pinning models for high-Tc superconductors are deduced. Magnetic relaxation and hysteresis studies have been performed on a zone-melted YBa2Cu3O6+x sample by SQUID. Nonlogarithmic magnetization decay is observed at relatively high temperatures; we attribute this to the nonlinear U(J) relationship which may arise from the local pinning potential Up(x), rather than collective pinning. At 70 K, the experimental data fits extremely well to the expression M(t)=M0+a(T)ln ln(t/τ) which is the result of the exponential U(J) relationship. Based on this U(J) law, the local pinning potential is determined to be Up(x)=U0(x/x0)[1−ln (x/x0)]. The voltage–current E(J) resulting from the observed U(J) relationship, as well as the role of the Y2BaCuO5 (211) phase in zone-melted YBCO is discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358726
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  • 4
    Electronic Resource
    Electronic Resource
    Critical current and its determination on TlSr2Ca2Ba2Cu3Oy by ac susceptibility measurement (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 6394-6397 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method is proposed according to which critical current density Jc at various temperatures T and dc fields B is estimated on (Tl0.5Pb0.5)(Ba0.2Sr0.8)2Ca2Cu3Oy based upon the flux diffusion barrier heights U(J,B,T) determined by means of ac susceptibility measurement at different ac field amplitudes, frequencies, T, and B. Jc is also estimated by the dc hysteresis measurement and compared with the former. The high Jc(B,T) and Tc show that this Tl-based superconductor is one of the more promising high-Tc materials from a practical standpoint. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359112
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of the superconducting thin film of HgBa2Ca2Cu3O8+δ (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1723-1725 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: HgBa2Ca2Cu3O8+δ (Hg-1223) superconducting thin films of about 0.3 μm in thickness have been successfully synthesized. The process involves depositing films (∼ 1 μm thickness) of Ba2Ca2Cu3Ox on a SrTiO3 substrate by pulse laser ablation technique and implanting mercury ions into this deposited film, followed by annealing at oxygen atmosphere. The films so obtained show a relatively wide superconducting transition temperature up to 118 K, as determined magnetically, which is similar to that of underdoping bulk Hg-1223. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115887
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of silver in Bi1.7Pb0.3Sr2−xAgxCa2Cu3Oy (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 545-547 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The oxide superconductor Bi1.7Pb0.3Sr2−xAgxCa2Cu3Oy has been synthesized under the ordinary pressure. The x-ray diffraction spectra of these specimens show the presence of only 2212 phase when x〈0.4, and the transition temperature achieved 99 K. With the x increase, the structure of sample transfers to 2223 phase. The investigation indicates that substitution of Sr2+ by Ag1+ increases the distance between layers. This may respond to Tc increase in 2212 phase and 2223 phase form at a relatively low temperature. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115183
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  • 7
    Electronic Resource
    Electronic Resource
    Improvement of beamline 4B9A and results of an X-ray diffraction experiment (1998)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 5 (1998), S. 503-505 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: 4B9A is a focusing and monochromatic photon beam at the BSRF, which was constructed in 1990. During the second phase of the BSRF program, the surface of the cylindrical mirror has been coated with Pt, covering the original Ni, and the monochromator has been upgraded. The maximum photon energy extends to 11 keV and the intensity has increased about tenfold with respect to the previous intensity at 6 keV. Synchrotron X-ray diffraction patterns for the Hg-1223 (HgBa2Ca2Cu3O8+δ) superconducting bulk and thin film have been measured at 1.54014 Å. Results indicate that the bulk and film can be indexed as possessing tetragonal symmetry; lattice parameters a = 3.856 Å and c = 15.851 Å for the bulk Hg-1223 compound, and a = 3.8517 Å and c = 15.8511 Å for the film. Their structures are similar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049597014477
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  • 8
    Electronic Resource
    Electronic Resource
    Voltage Relaxation and Its Influence on Critical Current Measurements (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 453-458 
    Details
    ISSN: 1572-9605
    Keywords: V-t curve ; I c measurement ; Ag-Bi2223 tapes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Based on the collective creep model, we numerically studied evolution of electric field and current density in superconductors and its influence on transport measurements of critical current. It is shown that many experimental facts, such as the dependence of V-I curves on sweeping rate of applied current and voltage relaxation are the results of this evolution. The simulation results are confirmed by electric transport measurements on Ag-sheathed Bi2−x Pb x Sr2Ca2Cu3O y tapes. Discussions on influences of the voltage relaxation on electric transport measurements including superconducting critical current are made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007715411727
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  • 9
    Electronic Resource
    Electronic Resource
    Field Distribution of a Cylinder-Shaped Type-II Superconductor with Limited Axial Length (1998)
    Springer
    Journal of superconductivity 11 (1998), S. 353-359 
    Details
    ISSN: 1572-9605
    Keywords: Field distribution ; type II superconductor ; cylindrical shape
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The self-field effects $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}} {B'}$$ of bulk magnetization current are considered when the applied field $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}} {B} _a$$ is parallel to the rotation axis of a cylinder-shaped type-II superconductor with limited axial length L and radius R, and by using finite-element analysis in a self-consistent way, the field-dependent magnetization current density function $$J_m (|B|)[\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}} {B} (\rho ,z) = \overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}} {B} _a + \overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}} {B'} (\rho ,z)]$$ , the current density, and the field distributions are derived from magnetic moment hysteresis loop m(B a) for the superconductor with full field penetration. When B a≫B p, the average field inside the cylinder $$\left\langle B \right\rangle = \mu _0 [H_a + f_c (L/2R)M]$$ in the Bean model approximation, and the function f c(L/2R) is quantitively given for arbitrary parameter L/2R, where B a=μ0 H a and M=m/(πR 2 L). In addition, the influences of the self-field on the measured m(B a) loop are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022698730604
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  • 10
    Electronic Resource
    Electronic Resource
    A Modal of Twin Domains in YBa2(Cu1−xCox)3Oy (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 129-136 
    Details
    ISSN: 1572-9605
    Keywords: twin domains ; YBCO ; Co-doping ; twin boundary ; model ; electron diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The existence of twin domains in YBa2(Cu1−x Co x )3O y samples was confirmed by many experiments. However, the physical picture of the twin domains has not been reported up to now. By analyzing oxygen content, Cu and Co valences, and Co coordination in those samples, we propose a domain model, which consists of two pairs of parallel zigzag Co-O chains surrounding orthorhombic cells, one along (110) direction and the other along (110) direction. The zigzag Co-O chains are the twin walls, with neighboring walls perpendicular and the opposite ones parallel. The distance between parallel walls (i.e., zigzag Co-O chains) depends upon Co concentration of sample. The twin domain model predicts the geometry, size, and absence of systematic symmetry of the domains. The model also predicts the modulation periodicity of electron diffraction patterns, which depends on Co concentration. All the predictions by the model agree well with the experimental results reported in literatures. Furthermore, the model indicates the possible existence of two domains, which have incommensurable modulation periodicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007742629820
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