Unconventional superconducting granularity of theY1−xPrxBa2Cu3

Abstract

We report on fluctuation magnetoconductivity and magnetic irreversibility of Y 1−x Pr x Ba 2 Cu 3 O 7−␦ single crystals and a polycrystalline sample. Although our samples are all single phase ͑orthorhombic͒ and the single crystals show no sign of structural inhomogeneity, all the samples exhibit two close and sharp genuine superconducting transitions. On the other hand, while the resistive transition of the polycrystalline sample exhibits in addition a coherence transition characteristic of a granular superconductor and the magnetic irreversibility displays the signature of the intergrain flux dynamics, the single crystals show no sign of these features. In view of these facts, we conclude that the well characterized split superconducting transition must result from a peculiar phase separation related with oxygen doping.

Fluctuation conductivity of polycrystalline Y1-xPr xBa2Cu3O7-delta superconductors

“…In this plot it is seen clearly that the transitions are different for air and vacuum processes. In air process, the transition width is approximately 4 K, while in vacuum process the width is about 9 K. Also, our data curves reveal a splitting of the bulk transition [11] for the air but not for the vacuum process. The upper (T C1 ) and lower (T C2 ) transitions appear in the temperature derivative as two narrow and prominent peaks.…”

“…In addition, the two close superconducting transitions were observed in Y 0.95 Pr 0.05 Ba 2 Cu 3 O 7−δ single crystals [11]. For the single crystals, which were observed by electronic microscopy, measurements of resistive transition and magnetic irreversibility the inhomogeneity hypothesis was completely excluded.…”

Conductivity fluctuations of polycrystalline Ag-doped YBa2Cu3O7-δ superconductor

“…The dynamics is described by the model E of Hohenberg and Halperin [24], where z = 1.5. This regime was also observed in polycrystalline and single-crystal samples [25][26][27]. Between T CO and T P , χ −1 σ is well described by a power law regime, given by the equation ∆σ ∝ (T − T CO ) −s , with s = 3.2 ± 0.2 (inset).…”

Analysis of fluctuation conductivity of polycrystalline Er1-xPr xBa2Cu3O7-δsuperconductors

“…2(b) suggest that Pr doping in-duces a superconducting phase with higher critical temperature (∼ 93.1 K). A genuine critical fluctuation regime in the temperature range between T P2 and T P1 was first observed by Barros et al in Y 1−x Pr x Ba 2 Cu 3 O 7−δ single crystals and polycrystalline samples [19,30], and it was associated with a peculiar phase separation related with oxygen doping. Panel 3(d) also shows that, between T P2 and T C0 , the variation of χ −1 σ as a function of temperature is well described by a power law regime with corresponding exponent s = 2.9 ± 0.3.…”

“…Careful studies of the conductivity in the neighborhood of the critical temperature can yield information about the nature of the superconducting state [14][15][16] as well as on the influence of the granularity at microscopic and mesoscopic levels on the fluctuation regimes [17][18][19]. In this paper, we report on fluctuations conductivity measurements in polycrystalline samples of the Er 1−x Pr x Ba 2 Cu 3 O 7−δ (0 ≤ x ≤ 0.10) superconductor.…”