Flux pinning and vortex transitions in doped BaFe2As2 single crystals

Abstract

The vortex liquid-to-glass transition has been studied in Ba0.72K0.28Fe2As2 (BaK-122), Ba(Fe0.91Co0.09)2As2(BaCo-122), and Ba(Fe0.95Ni0.05)2As2(BaNi-122) single crystal with superconducting transition temperature, Tc = 31.7, 17.3, and 18 K, respectively, by magnetoresistance measurements. For temperatures below Tc, the resistivity curves were measured in magnetic fields within the range of 0 ≤ B ≤ 13 T, and the pinning potential was scaled according to a modified model for vortex liquid resistivity. Good scaling of the resistivity ρ(B, T) and the effective pinning energy U0(B,T) were obtained. The vortex state is three-dimensional at temperatures lower than a characteristic temperature T*. The vortex phase diagram was determined based on the evolution of the vortex-glass transition temperature Tg with magnetic field and the upper critical field, Hc2. We found that non-magnetic K doping results in a high glass line close to the Hc2, while magnetic Ni and Co doping causes a low glass line which is far away from the Hc2. Our results suggest that non-magnetic induced disorder is more favourable for enhancement of pinning strength compared to magnetic induced disorder. Our results show that the pinning potential is responsible for the difference in the glass states.

High field superconducting properties of Ba(Fe1−xCox)2As2 thin films

“…8, shows clear differences for (left) and (right): For , the irreversibility field can be well described by a simple power law of the form with 4/3 (red line). Similar power laws for at high temperatures have been measured for Co-doped Ba-122 single crystals by resistive53 and AC susceptibility measurements54. In contrast, seems to be strongly influenced by the temperature dependence of as well as the extended planar defects.…”

Vortex glass-liquid transition and activated flux motion in an epitaxial, superconducting NdFeAs(O,F) thin film

“…A similar scaling approach by Andersson et al [25] with temperature scale [T(T c -T g )/T g (T c -T)]-1 also does not lead to scaling for this sample and, furthermore, does not resolve the critical region correctly. The latter scaling approach has nonetheless been successfully applied to Ba122 single crystals [26] and (Li 1−x Fe x OH)FeSe [27]. The red lines in Fig.…”

Nematicity in the superconducting mixed state of strain detwinned underdoped Ba( Fe1−xCox)2As2

“…The liquid-glass temperature transition T g can be obtained by means of a non-linear fit, taking into account the critical behaviour of the resistivity ρ(H, T ) at T g . An alternative way 36 , proposes a scaling of the resistivity ρ(H, T ), by assuming that the glass transition occurs when thermal and pinning energy scales match. This scaling procedure has been performed, in order to obtain the best T g for each θ direction, at H 0 = 5 kOe and under different strain conditions (F, CS and TS).…”