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Author (down) Haberkorn, N.; Suárez, S.; Bud'ko, S.L.; Canfield, P.C.
Title Strong pinning and slow flux creep relaxation in Co-doped CaFe2As2 single crystals Type Journal Article
Year 2020 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume 318 Issue Pages 113963
Keywords Iron based superconductors; Single crystals; Vortex dynamics; Magnetization
Abstract We report on measurements of critical current densities Jc and flux creep rates S of freestanding Ca(Fe1−xCox)2As2 (x ≈ 0.033) single crystals with Tc ≈ 15.7 K by performing magnetization measurements. The magnetic field dependences of Jc at low temperature display features related to strong pinning. In addition, we find that the system displays small flux creep rates. The characteristic glassy exponent, μ, and the pinning energy, U0, display exceptional high values for pristine crystals. We find that for magnetic fields between 0.3 T and 1 T, μ decreases from ≈ 2.8 to ≈ 2 and U0 remains ≈ 300 K. Analysis of the pinning force indicates that the mechanism is similar to the observed in polycrystalline systems in which grain boundaries and random disorder produce the vortex pinning. Considering the large U0 observed in the single crystal, we attempt to improve the pinning by adding random point disorder by 3 MeV proton irradiation with a fluence of 2 × 1016 proton/cm2. The results show that, unlike other iron-based superconductors, the superconducting fraction is sharply reduced by irradiation. This fact indicates that the superconductivity in the system is extremely fragile to an increment in the disorder. The superconducting volume fraction in the irradiated crystal systematically recovers after removal disorder by thermal annealing, which evidences as to the observation of critical state in curves of magnetization versus magnetic field. No features related to a reentrant antiferromagnetic transition are observed for the irradiated sample.
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ISSN 0038-1098 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ Serial 859
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Author (down) Bud'ko, S.L.; Nakamura, O.; Guimpel, J.; Maple, M.; Schuller, I.K.
Title Anisotropic pressure dependence of the critical temperature of REBa2Cu3O7−δ Type Journal Article
Year 1991 Publication Physica C: Superconductivity Abbreviated Journal
Volume 185-189, Part 3 Issue Pages 1947-1948
Keywords
Abstract The hydrostatic pressure dependence of the superconducting critical temperature, Tc, was measured in highly crystalline oriented REBa2Cu3O7−δ (RE=Yb, Dy, Y, Gd) thin films grown on different substrates. The anisotropic strain field induced by the substrate and the different crystalline orientations of the films allows the three strain derivatives of the critical temperature to be estimated. A large anisotropy is found in the ab plane with Tc increasing on compression parallel to the CuO chains and decreasing on compression perpendicular to them. The results on c textured films indicate a non linear relation between Tc and the microscopic parameter which determines its pressure dependence.
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Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0921-4534 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ jguimpel @ Serial 616
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