Dynamic contribution to the fishtail effect in a twin-free DyBa2Cu3O7-δ single crystal

A. J.J. van Dalen, M. R. Koblischka, R. Griessen, M. Jirsa, G. Ravi Kumar

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Superconducting current densities js and dynamic relaxation rates Q d ln js/d In(dBe/dt), where dBe/dt is the sweep rate of the external magnetic field Be, were measured as a function of temperature (5 K < T < 65 K) in magnetic fields up to 7 T on a twin-free DyBa2Cu3O7-δ single crystal by means of a high-sensitivity capacitance torque magnetometer. Above 15 K, we observe a "fishtail" effect, i.e. a pronounced minimum in the js(Be) curve at fields around Be = 1 T. The relaxation rate Q shows an anomalous increase at low fields which is correlated to the minimum in the js(Be) curve. Both the js versus Be and Q versus Be data are used as input parameters into the generalized inversion scheme developed by Schnack et al. [Phys. Rev. B 48 (1993) 13178] to calculate the true critical current density jc which is by definition independent of relaxation effects. Interestingly, the jc(Be, T) curves derived in this way do not show a minimum. This points clearly to a dynamic contribution to the fishtail effect. The true critical current density jc(Be, T) decreases weakly with increasing Be over the entire measured temperature and field range, as expected for single-vortex pinning. This indicates that the observed fishtail effect is not caused by a crossover from single-vortex pinning to pinning of flux bundles. The temperature dependence of jc is in good agreement with the predictions of a model based on single-vortex pinning caused by spatial fluctuations in the charge-carrier mean free path.

Original languageEnglish
Pages (from-to)265-274
Number of pages10
JournalPhysica C: Superconductivity and its applications
Volume250
Issue number3-4
DOIs
Publication statusPublished - 1995 Aug 15

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering

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