Magnetization relaxation, critical current density and vortex dynamics in a Ba${}_{0.66}$K${}_{0.32}$BiO${}_{3+\delta }$ single crystal

Abstract

We have conducted extensive investigations on the magnetization and its dynamical relaxation on a Ba${}_{0.66}$K${}_{0.32}$BiO${}_{3+\delta }$ 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 $U_{\mathrm{c}}$ 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 YBa${}_2$Cu${}_3$O${}_7$; (2) Associated with the second peak effect, the magnetization relaxation rate is inversely related to the transient superconducting current density $J_{\mathrm{s}}$ 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 $\mu$ and a small intrinsic pinning potential $U_{\mathrm{c}}$; (4) Investigation on the volume pinning force density shows that the data can be scaled to the formula $F_p\propto b^p(1-b{)}^q$ 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 $b\approx 0.47$. Finally, a vortex phase diagram is drawn for showing the phase transitions or crossovers between different vortex phases.

9 pages,10 figures

References in corpus (5)

• Vortex phase diagram of Ba(Fe0.93Co0.07)2As2 single crystals
• Fishtail effect and the vortex phase diagram of single crystal Ba0.6K0.4Fe2As2
• Critical Fields and Anisotropy of NdO0.82F0.18FeAs Single Crystals
• Magnetization Relaxation and Collective Vortex Pinning in the Fe-Based Superconductor SmFeAsO_0.9F_0.1
• Vortex creep and critical current densities in superconducting (Ba,K)Fe${}_2$As${}_2$ single crystals

Cited by in corpus (2)

• Anomalous second magnetization peak in 12442-type RbCa${}_2$Fe${}_4$As${}_4$F${}_2$ superconductors
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