Crossover effects in the temperature dependence of the critical current in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}

Journal Article · Sat Jun 01 04:00:00 EDT 1996 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.53.14621· OSTI ID:284399

Darhmaoui, H; Jung, J ^[1]

---

1. Department of Physics, University of Alberta, Edmonton, Alberta, T6G2J1 (CANADA)

Temperature dependence of the critical current {ital I}{sub {ital c}} was investigated in thin films and ceramics of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) over a temperature range 10{endash}90 K and in magnetic fields up to 700 G. The measurements were performed using superconducting rings in a persistent mode. A scanning axial Hall probe was used to record the profile of the magnetic field across the ring, generated by the persistent current at the critical level. The magnitude of {ital I}{sub {ital c}} was inferred from the magnitude of the persistent current{close_quote}s self-field in the center of the ring. This technique eliminated the contribution of normal currents to the measured value of {ital I}{sub {ital c}} and allowed us to distinguish between depairing and depinning critical currents. The results revealed the crossover between an Ambegaokar-Baratoff-like temperature dependence of the critical current to a Ginzburg-Landau dependence. The crossover was observed for both depairing and depinning critical currents in {ital c}-axis-oriented YBCO thin films during reduction of {ital T}{sub {ital c}} from 91 down to 87 K and in a ceramic YBCO upon application of small magnetic fields. The experimental data imply the presence of superconducting microdomains of an effective diameter of about 30{endash}40 A, coupled by Josephson tunnel junctions, inside the grains and in the intergrain microbridges of YBCO, in agreement with the Clem{close_quote}s model for {ital I}{sub {ital c}}({ital T}) in strongly coupled granular superconductors [Clem {ital et} {ital al}., Phys. Rev. B {bold 35}, 6637 (1987)]. The size of these domains decreases with a decreasing oxygen content and with an increasing applied magnetic field. {copyright} {ital 1996 The American Physical Society.}

• OSTI ID: 284399
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 21 Vol. 53; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
BARIUM OXIDES
COPPER OXIDES
CRITICAL CURRENT
HIGH-TC SUPERCONDUCTORS
JOSEPHSON EFFECT
MAGNETIC FIELDS
SUPERCONDUCTING FILMS
TEMPERATURE DEPENDENCE
YTTRIUM OXIDES