## 抄録

Induced current densities j_{s} and flux relaxation of a Bi_{2}Sr_{2}CaCu_{2}O_{8} single crystal have been measured in detail as a function of temperature from T = 1.6 K up to the irreversibility temperature T_{irr} in magnetic fields up to 7 T by means of sensitive capacitance torquemeters. The dynamical relaxation rate Q ≡ d ln j_{s}/d ln(dB_{e}/dt) does not extrapolate to zero at T = 0 K, demonstrating the presence of quantum creep. The quantum creep rate Q(0) ≈ 0.03 at T = 0 is similar to values found in YBa_{2}Cu_{3}O_{7} films, although Bi_{2}Sr_{2}CaCu_{2}O_{8} is much more anisotropic than YBa_{2}Cu_{3}O_{7}. The weak field dependence of Q(0) is consistent with tunneling of 2D vortex pancakes. The induced current density j_{s}, the dynamical relaxation rate and the conventional relaxation rate R ≡ -d ln j_{s}/d ln t monitoring the time decay of j_{s} at fixed external field, are measured as a function of the field strength and its orientation with respect to the sample in detail at a fixed temperature T = 20 K. The observed non-logarithmic time dependence of j_{s} is analysed by means of a collective pinning theory. This analysis gives a good description of the observed time dependence of j_{s}, even for extremely fast relaxation processes leading to j_{s}(t)/j_{s}(0) < 0.01 in times as small as 10 s. The characteristic pinning energy U_{c}, obtained by fitting the observed time decay of j_{s} with a collective-creep model scales approximately with the c-axis component B_{e} cos Θ of the magnetic field. This scaling behaviour is also observed in the angular dependence of Q and j_{s}. For the scaling of j_{s} one has to take into account that the current is induced by only the c-axis component of the sweep rate.

本文言語 | English |
---|---|

ページ（範囲） | 271-283 |

ページ数 | 13 |

ジャーナル | Physica C: Superconductivity and its applications |

巻 | 257 |

号 | 3-4 |

DOI | |

出版ステータス | Published - 1996 2月 1 |

外部発表 | はい |

## ASJC Scopus subject areas

- 電子材料、光学材料、および磁性材料
- 凝縮系物理学
- エネルギー工学および電力技術
- 電子工学および電気工学

## フィンガープリント

「Quantum creep and fast thermally activated vortex dynamics in a Bi_{2}Sr

_{2}CaCu

_{2}O

_{8}single crystal」の研究トピックを掘り下げます。これらがまとまってユニークなフィンガープリントを構成します。