Magnetization relaxation, critical current density, and vortex dynamics in a Ba0.66K0.32BiO3+delta single crystal

Article

关键词: HIGH-TEMPERATURE SUPERCONDUCTORS;    BA-CU-O;    TL2BA2CACU2O8 THIN-FILMS;    FLUX-CREEP;    GLASS SUPERCONDUCTIVITY;    HARD SUPERCONDUCTORS;    TRANSPORT-PROPERTIES;    YBA2CU4O8 FILMS;    CRITICAL FIELDS;    LATTICE;   

DOI  :  10.1103/PhysRevB.91.214516

来源: SCIE

【 摘 要 】

We have conducted extensive investigations on the magnetization and its dynamical relaxation on a Ba0.66K0.32BiO3+delta single crystal. It is found that the magnetization-relaxation rate is rather weak compared to that in cuprate superconductors, indicating a higher collective vortex pinning potential (or activation energy), although the intrinsic pinning potential U-c is weaker. A 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 2 to 24 K. Its general behavior is similar to that in YBa2Cu3O7. (2) Associated with the second-peak effect, themagnetization-relaxation rate is inversely related to the transient superconducting current density J(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-c. (4) Investigation on the volume pinning force density shows that the data can be scaled to the formula F-p proportional to b(p) (1 - b)(q), with p = 2.79 and q = 3.14, where b is the reduced magnetic field to the irreversible magnetic field. The maximum normalized pinning force density appears near b approximate to 0.47. Finally, a vortex phase diagram is drawn to show the phase transitions or crossovers between different vortex phases.

【 授权许可】

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