Fishtail effect and the vortex phase diagram of single crystal Ba0.6K0.4Fe2As2

Abstract

By measuring the magnetization hysteresis loops of superconducting Ba0.6K0.4Fe2As2 single crystals, we obtained the high upper critical field and large current carrying ability which point to optimistic applications. The fishtail (or second peak) effect is also found in the material, and the position of the vortex pinning force shows a maximum at 1/3 of the reduced field, being consistent with the picture of vortex pinning by small size normal cores in the sample. Together with the resistive measurements, for the first time the vortex phase diagram is obtained for superconductor Ba0.6K0.4Fe2As2.

Flux pinning mechanism in BaFe1.9Ni0.1As2 single crystals: Evidence for fluctuation in mean free path induced pinning

“…34 The SMP can be observed at all temperatures below 15 K, similar to the behaviour of (Ba,K)Fe 2 As 2 (Ref. 23) and BaFe 1Àx Co x As 2 crystals. 31 Arrows indicate the onset ðB onset SMP Þ and peak ðB peak SMP Þ positions of the SMP in Fig.…”

“…38 It is likely that the SMP has the same mechanism in both compounds. 23 In Fig. 3, we present the vortex phase diagram of the BaFe 1.9 Ni 0.1 As 2 crystal.…”

“…The SMP has also been observed in optimally doped Ba 1Àx K x Fe 2 As 2 . 19,23 However, it is worth to note that most form of in-homogeneity like T c variation, impurity phase, doping variation, etc., might prevent the occurrence of SMP. 24 For example, an under-doped Ba 1Àx K x Fe 2 As 2 system does not show the SMP.…”

“…31 Furthermore, It has been suggested that the very large J c and fishtail effect at high temperature below T c in Ba 0.6 K 0.4 Fe 2 As 2 had originated from the smallsize normal core pinning centres. 23 In this work, we present a systematic study of the flux pinning mechanism of BaFe 1.9 Ni 0.1 As 2 crystals.…”

Critical current density and vortex pinning mechanism of Lix(NH3)yFe2Te${}_{1.2}$Se${}_{0.8}$ single crystals

“…Interestingly, similar values of p and q have also been observed in FeS and FeS 0.94 Se 0.06 single crystals prepared by deintercalating potassium from K x Fe 2−y (S, Se) 2 using the hydrothermal method [29]. It suggests that there is a common type of pinning centers in these materials in contrast to FeSe 0.5 Te 0.5 thin films, K x Fe 2−y Se 2 , and Ba 0.6 K 0.4 Fe 2 As 2 where the point-like defects with normal core are the dominant pinning sources [24,26,30]. Moreover, the F max p can be fitted using F max Fig.…”