Flux dynamics associated with the second magnetization peak in the iron pnictideBa1−xKxFe2As<

Abstract

We report on isofield magnetic relaxation data on a single crystal of Ba 1−x K x Fe 2 As 2 with superconducting transition temperature T c = 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, M͑t͒, was used to obtain the activation energy U͑M͒ 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 M͑H͒ curves demonstrate that the irreversibility as well the second magnetization peak position, H p ͑T͒, are time dependent and controlled by plastic motion of the vortex state. In the region delimited by a characteristic field Hon

Magnetic relaxation and collective vortex creep in FeTe 0.6 Se 0.4 single crystal

“…4(a). The evaluated value of µ is ∼ 1.34 close to that reported in YBa 2 Cu 3 O 7−δ [33], and IBSs [10,12,20]. The value of µ resides between the prediction of singlevortex (1/7) and small-bundle (5/2) regimes, indicating that contributions of those two kinds of pinnings coexist.…”

“…Magnetic relaxation measurements in IBSs reported so far have revealed that they also show giant flux creep and collective pinning, which implies that IBSs and cuprate superconductors may share common vortex physics [7][8][9][10][11][12][13]. Until now, most detailed studies about the vortex dynamics on IBSs have been performed on "122" phase since high-quality single crystals are readily available.…”

Temperature and time scaling of the peak-effect vortex configuration in FeTe0.7Se0.3

“…23,24 However, significant differences in the second-peak features have been observed within this family: in the highly anisotropic Bi-2212 and Bi-2223 the peak is sharp and temperature independent [25][26][27][28][29] while in Bi-2201 crystals it exhibits a strong temperature dependence. 30 Regarding the iron-based superconductors, the peak effect has been observed in FeAs-1111, [31][32][33] in FeAs-122, [34][35][36][37][38] and in FeTe 1−x Se x , 39 even if a clear understanding of the physical origin of the phenomenon in this family has not been achieved yet. However, since it has been shown by small angle neutron scattering, [40][41][42] Bitter decoration, 40 and magnetic force microscopy 41 that an ordered vortex lattice is not present in these compounds, the origin of the peak effect due to a phase transition of the vortex lattice seems to be excluded.…”

Magnetization hysteresis and time decay measurements in FeSe0.50Te0.50: Evidence for fluctuation in mean free path induced pinning

“…The observation of H irr (T ) values lying well below the H c2 (T ) values over the entire H-T vortex phase diagram has been a distinct feature seen in a wide variety of low-T c and high-T c superconductors [33][34][35][36][37][38][39]. Here it is worthwhile to look at its ramifications on the exponents within the Dew-Hughes scenario for the iron chalcogenide superconductor under consideration.…”