Flux dynamics associated with the second magnetization peak in the iron pnictide Ba1−xKxFe2As2

Abstract

We report on isofield magnetic relaxation data on a single crystal of Ba1−xKxFe2As2 with superconducting transition temperature Tc=32.7 K which exhibit the so-called fish-tail effect. A surface map of the superconducting transition temperature shows that the superconducting properties are close to homogeneous across the sample. Magnetic relaxation data, M(t), was used to obtain the activation energy U(M) in order to study different vortex-dynamics regimes. Results of this analysis along with time-dependent measurements as a function of field and temperature extended to the reversible region of some M(H) curves demonstrate that the irreversibility as well the second magnetization peak position, Hp(T), are time dependent and controlled by plastic motion of the vortex state. In the region delimited by a characteristic field Hon (well below Hp), and Hp, the vortex dynamics is controlled by collective pinning. For fields below Hon the activation energy, U0, increases with field as expected for collective pinning, but the pinning mechanism is likely to be in the single vortex limit.

Source-reported materials — not catalogue approval

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