Critical-state flux penetration and linear microwave vortex response in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} films

Journal Article · Sat Nov 01 04:00:00 EST 1997 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.56.11989· OSTI ID:544955

Willemsen, B A ^[1]; Derov, J S ^[2]; Sridhar, S ^[1]

---

1. Physics Department, Northeastern University, Boston, Massachusetts 02115 (United States)
2. Rome Laboratory, Hanscom AFB, Bedford, Massachusetts 01731 (United States)

The vortex contribution to the dc magnetic field (H) dependence of the microwave surface impedance {tilde Z}{sub s}(H)=R{sub s}(H)+iX{sub s}(H) of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} thin films was measured using suspended patterned resonators. {tilde Z}{sub s}(H) is shown to be a direct measure of the flux density B(H) enabling a very precise test of models of flux penetration. Three regimes of field-dependent behavior were observed: (1) Initial flux penetration occurs on very low-field scales H{sub i}(4.2K){approximately}10mT, (2) at moderate fields the flux penetration into the virgin state is in excellent agreement with calculations based upon the {ital field-induced} Bean critical state for thin-film geometry, parametrized by a field scale H{sub s}(4.2K){approximately}J{sub c}d{approximately}0.5T, and (3) for very high fields H{gt}H{sub s}, the flux density is uniform and the measurements enable direct determination of vortex parameters such as pinning force constants {alpha}{sub p} and vortex viscosity {eta}. However, hysteresis loops are in disagreement with the thin-film Bean model, and instead are governed by the low-field scale H{sub i}, rather than by H{sub s}. Geometric barriers are insufficient to account for the hysteresis loops. {copyright} {ital 1997} {ital The American Physical Society}

• OSTI ID: 544955
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 18 Vol. 56; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
COPPER OXIDES
ELECTRIC IMPEDANCE
FLUX DENSITY
HIGH-TC SUPERCONDUCTORS
HYSTERESIS
MAGNETIC FLUX
PENETRATION DEPTH
SUPERCONDUCTING FILMS
THIN FILMS
VORTICES
YTTRIUM OXIDES