1. Twofold role of columnar defects in iron based superconductors.
- Author
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Torsello, D, Gerbaldo, R, Gozzelino, L, Laviano, F, Takahashi, A, Park, A, Pyon, S, Ichinose, A, Tamegai, T, and Ghigo, G
- Subjects
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SUPERCONDUCTING quantum interference devices , *IRON-based superconductors , *SCANNING transmission electron microscopy , *PARTICLE tracks (Nuclear physics) , *IRON alloys , *CRITICAL currents , *SURFACE impedance - Abstract
We report on the introduction of columnar defects in Ba1−xKxFe2As2 and BaFe2(As1−xPx)2 single crystals via 1.2 GeV Pb irradiation. Scanning transmission electron microscopy analysis proves the formation of continuous defects along the ion tracks, with a diameter of about 3 nm, and a planar density compatible with the irradiation fluence. The twofold role of such defects, i.e. as pair breakers as well as pinning centers, is investigated by a microwave technique, allowing us to determine critical temperature Tc, surface impedance and penetration depth λL, and by magneto-optical imaging and superconducting quantum interference device magnetometry to evaluate the critical current density Jc. The decrease of Tc is quite modest and, together with λL modifications, testifies the increase of pair-breaking scattering following irradiation. The dependence of Jc on irradiation dose and temperature is due to the pinning landscape induced by the columnar defects, and shows the existence of an optimal irradiation dose to enhance the critical current. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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