Magnetization relaxation, critical current density, and vortex dynamics in aBa0.66K0.32BiO3+δsingle crystal

Abstract

We have conducted extensive investigations on the magnetization and its dynamical relaxation on a Ba0.66K0.32BiO 3+δ single crystal. It is found that the magnetization relaxation rate is rather weak compared with that in the cuprate superconductors, indicating a higher collective vortex pinning potential (or activation energy), although the intrinsic pinning potential Uc is weaker. Detailed analysis leads to the following discoveries: (1) A second-peak effect on the magnetization-hysteresis-loop was observed in a very wide temperature region, ranging from 2K to 24K. Its general behavior looks like that in YBa2Cu3O7; (2) Associated with the second peak effect, the magnetization relaxation rate is inversely related to the transient superconducting current density Js revealing a quite general and similar mechanism for the second peak effect in many high temperature superconductors; (3) A detailed analysis based on the collective creep model reveals a large glassy exponent µ and a small intrinsic pinning potential Uc; (4) Investigation on the volume pinning force density shows that the data can be scaled to the formula Fp ∝ b p (1 − b) q with p = 2.79 and q = 3.14, here b is the reduced magnetic field to the irreversible magnetic field. The maximum normalized pinning force density appears near b ≈ 0.47. Finally, a vortex phase diagram is drawn for showing the phase transitions or crossovers between different vortex phases. PACS numbers: 74.70.-b, 74.25.Ha, 74.25.Wx, 74.25.Uv U (J s , T, B e ) = U c (T, B e ) µ(T, B e ) [( J c (T, B e ) J s (T, B e ) ) µ(T,Be) − 1] (2)

Flux pinning and relaxation in FeSe0.5Te0.5single crystals

“…This feature reminds us that the second peak effect is also likely to be closely related to the vortex dynamics. Our result is very similar to other reports [30,31].…”

Anomalous Second Magnetization Peak in 12442-Type RbCa2Fe4As4F2 Superconductors

“…Similar results have been observed in other superconductors such as Ba0.68K0.32Fe2As2 (ℎmax ∼ 0.43), [39] BaFe1.9Ni0.1As2 (ℎmax ∼ 0.4), [40,41] and Ba0.66K0.32BiO 3+𝛿 (ℎmax ∼ 0.47). [42] According to the Dew-Hughes model, [35] the present case of ℎmax < 0.5 is suggestive of 𝛿𝑙-type pinning, which arises from a spatial variation in the mean free path of charge carriers, and the pinning is due to the presence of a large density of pointlike defect centers whose dimensions are smaller than the intervortex distance. In addition, the peaks in the low field region are located at ℎmax ∼ 0.2, which is the characteristic of surface strong pinning, such as the planar defects.…”

Anomalously small magnetic relaxation rate of Ca10(Pt3As8)(Fe2−x Pt x As2)5 superconductor

“…Therefore, we have summarized the results from relevant literature [1,27,33,34,[57][58][59][60][61][62][63][64][65][66], including low-temperature superconductors, iron-based superconductors, and cuprates, and depict a relation diagram of S and Gi 1/2 . Figure 5 shows the distribution of the corresponding S with a wide range of Gi values in the case of T = T c /4, µ 0 H = 1 T. The universal lower limit of S ∼ Gi 1/2 (T/T c ) is represented by a solid line.…”