Percolation effects and oxygen inhomogeneities in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">YBa</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:ma

Osofsky, M. S.; Cohn, J. L.; Skelton, E. F.; Miller, M. M.; Soulen, R. J.; Wolf, Stuart A.; Vanderah, Terrell A.

doi:10.1103/physrevb.45.4916

Cited by 95 publications

(20 citation statements)

References 15 publications

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“…Several reports suggest that the peak effect can be explained by the collective pinning and creep model [29,38,39]. Another possible reason is that the weak linked areas [40] in sample B-F are suppressed or driven normal with the increment of applied fields, and they may act as pinning centers similar to the role of oxygen deficiency in YBCO [41,42]. Recently, the peak effect of J cm (B) in oxypnictide polycrystal [36] and single crystal [43] was verified to be caused by a first order phase transition from a ordered "elastically pinned" low-field vortex phase to a high-field disordered phase.…”

Section: Density Effect On Critical Current Densitymentioning

confidence: 99%

Density effect on critical current density and flux pinning properties of polycrystalline SmFeAsO_{1 −x}F_xsuperconductor

Ding

Sun

Zhuang

et al. 2011

Supercond. Sci. Technol.

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A series of polycrystalline SmFeAs 1-x O x bulks was prepared to systematically investigate the influence of sample density on flux pinning properties. Different sample densities were achieved by controlling the pelletizing pressure. The superconducting volume fraction, the critical current densities J cm and the flux pinning force densities F p were estimated from the magnetization measurements. Experimental results manifest that: (1) the superconducting volume fraction increases with the increasing of sample density. (2) The J cm values have the similar trend except for the sample with very high density may due to different connectivity and pinning mechanism. Moreover, The J cm (B) curve develops a peak effect at approximately the same field at which the high-density sample shows a kink. (3) The F p (B) curve of the 2 high-density sample shows a low-field peak and a high-field peak at several temperatures, which can be explained by improved intergranular current, while only one peak can be observed in F p (B) of the low-density samples. Based on the scaling behaviour of flux pinning force densities, the main intragranular pinning is normal point pinning.

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Section: Density Effect On Critical Current Densitymentioning

confidence: 99%

Density effect on critical current density and flux pinning properties of polycrystalline SmFeAsO_{1 −x}F_xsuperconductor

Ding

Sun

Zhuang

et al. 2011

Supercond. Sci. Technol.

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“…The full width at half maximum (FWHM) values range between 132 and 514 arcseconds. Assuming that the broadening is due to presence of random arrays of dislocations, their density can be estimated from the following equation:28'29 4.35b (2) where f3 is the FWHM in radians and b is the length of the Burgers vector and in this case is taken as d, the spacing between the (006) planes. The dislocation density is estimated to be between 2.5 x 108 to 3.8 x i09 lines/cm2.…”

Section: °Fmentioning

confidence: 99%

Structural inhomogeneities in crystals of YBa 2 Cu 3 0 7-δ

Osofsky

Qadri

Skelton

et al. 1996

Oxide Superconductor Physics and Nano-Engineering II

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Structural inhomogeneities in crystals of YBa2Cu3O75 are characterized using high resolution x-ray diffraction. Rocking curves and a high resolution specular radial scan show features indicating that the crystals are not truly "single." The high resolution radial scan of a crystal that had a superconducting transition width of only one-half Kelvin, as determined by ac susceptibility, and appeared to be free of gross defects, when examined with conventional x-ray diffraction techniques, shows a distribution in the c-axis lattice parameter. These results suggest that crystals with sharp transitions should be carefully examined for the presence of structural anomalies which might influence the superconductive properties.High temperature superconductors (HTS) still present many puzzles to researchers studying their various physical properties. Many experimental studies exploring the nature of both vortex dynamics and the mechanism of superconductivity have revealed unusual behaviors which have spawned, or apparently confirmed, many theories. The results of several studies have suggested the presence of inhomogeneities in polycrystalline samples,1 crystals2'3'4'5'6'7'8'9 and films10 of YBa2Cu3O7 (YBCO). When coupled with the behaviors mentioned above, this suggests that some, if not all, of the new phenomena may be extrinsic. Such sensitivity of superconductive properties to sample imperfections is to be expected due to the short superconducting coherence lengths of the materials, their low carrier concentrations, and the strong dependence of those carrier concentrations on the oxygen content of a sample. i1 has shown theoretically that such sample inhomogeneities can explain many of the properties of these systems and has suggested that they are responsible for the high Ta's. In this report we show that "single" crystals with various oxygen content have rocking curves with structure. Furthermore, we directly show, using high resolution x-ray diffraction, that a crystal with a sharp superconducting transition, and which appears to be homogeneous with conventional x-ray diffraction measurements, in fact contains several distinct domains with different c-lattice parameters and rocking curves with significant structure.As is well known, the superconducting properties of YBCO are strongly affected by the oxygen composition and the details of the oxygen ordering. In general, superconductivity occurs for < 0.6 with T increasing to 93 K as decreases from 0.6 to 0. Under certain processing conditions12'13'14'15'16'17'18'19 the curve of superconducting transition temperature, T, versus has several plateaus, one near ö =0 corresponding to T 90 K (the ortho-I phase) and others with lower Ta's, the most studied being the one near = 0.5 with a T of 60 K (the ortho-Il phase). These different superconducting transitions, which can be quite sharp, have been attributed to the ordering of the chain oxygens. This argument is supported by x-ray, neutron, and electron diffraction measurements.If the chains are not ordered, then T still de...

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“…Since ⌬M is proportional to the critical current density, 3 several authors proposed that an increase in the efficiency of pinning centers with increasing magnetic fields could lead to the appearance of the second magnetization peak. 2,4,5 This was emphasized by fast magnetization measurements using pulsed field and vibrating sample magnetometer measurements, 6 which revealed the SMP even at very short time windows. Such nonmonotonic dependence of the critical current with the applied field could be of great technological interest, since it could be used to improve the performance of superconducting devices.…”

Section: Introductionmentioning

confidence: 98%

Fishtail effect studied by ac susceptibility in ErBa2Cu3O7−δ single crystal

Cardoso

Lima

2004

Journal of Applied Physics

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The second magnetization peak (SMP), also known as the fishtail effect, is studied by a scaling procedure for ac susceptibility measurements. From this scaling law the frequency dependence of the critical current J(ν) and the flux creep exponent n can be determined. A striking correlation between n and the SMP is observed, which indicates a clear change in the rate of flux creep around the peak position. This result points to the relevance of the dynamical contribution for the peak formation. However, we could not observe a transition between two different regimes of vortex motion at the SMP. The dependence of the SMP with sample dimensions is also discussed.

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Percolation effects and oxygen inhomogeneities inYBa2Cu3

Cited by 95 publications

References 15 publications

Density effect on critical current density and flux pinning properties of polycrystalline SmFeAsO_{1 −x}F_xsuperconductor

Density effect on critical current density and flux pinning properties of polycrystalline SmFeAsO_{1 −x}F_xsuperconductor

Structural inhomogeneities in crystals of YBa 2 Cu 3 0 7-δ

Fishtail effect studied by ac susceptibility in ErBa2Cu3O7−δ single crystal

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Percolation effects and oxygen inhomogeneities inYBa2Cu3

Cited by 95 publications

References 15 publications

Density effect on critical current density and flux pinning properties of polycrystalline SmFeAsO1 −xFxsuperconductor

Density effect on critical current density and flux pinning properties of polycrystalline SmFeAsO1 −xFxsuperconductor

Structural inhomogeneities in crystals of YBa 2 Cu 3 0 7-δ

Fishtail effect studied by ac susceptibility in ErBa2Cu3O7−δ single crystal

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Product

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Density effect on critical current density and flux pinning properties of polycrystalline SmFeAsO_{1 −x}F_xsuperconductor

Density effect on critical current density and flux pinning properties of polycrystalline SmFeAsO_{1 −x}F_xsuperconductor