Vortex creep and critical current densities in superconducting (Ba,K)Fe${}_2$As${}_2$ single crystals

Abstract

The surprisingly rapid relaxation of the sustainable current density in the critical state of single crystalline Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ is investigated for magnetic fields oriented parallel to the c-axis and to the $ab$--plane respectively. Due to the inadequacy of standard analysis procedures developed for flux creep in the high temperature superconducting cuprates, we develop a simple, straightforward data treatment technique that reveals the creep mechanism and the creep exponent $\mu$. At low magnetic fields, below the second magnetization peak, $\mu$ varies only slightly as function of temperature and magnetic flux density $B$. From the data, we determine the temperature- and field dependence of the effective activation barrier for creep. At low temperatures, the measured current density approaches the zero--temperature critical current density (in the absence of creep) to within a factor 2, thus lending credence to earlier conclusions drawn with respect to the pinning mechanism. The comparable values of the experimental screening current density and the zero-temperature critical current density reveals the limited usefulness of the widely used "interpolation formula".

Physical Review B (2012) Accepted

References in corpus (6)

• Vortex phase diagram of Ba(Fe0.93Co0.07)2As2 single crystals
• Fishtail effect and the vortex phase diagram of single crystal Ba0.6K0.4Fe2As2
• Observation of Lattice and Andreev Bound States of Vortices in Ba0.6K0.4Fe2As2 Single Crystals with Scanning Tunneling Microscopy/Spectroscopy
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• Flux pinning in (1111) iron-pnictide superconducting crystals
• Magnetization Relaxation and Collective Vortex Pinning in the Fe-Based Superconductor SmFeAsO_0.9F_0.1

Cited by in corpus (1)

• Disorder, critical currents, and vortex pinning energies in isovalently substituted BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$