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Author (up) Van Dalen, A.J.J.; Griessen, R.; Libbrecht, S.; Bruynseraede, Y.; Osquiguil, E. url  openurl
  Title Quantum creep and pinning properties of oxygen-deficient YBa2Cu3Oxn films Type Journal Article
  Year 1996 Publication Physical Review B – Condensed Matter and Materials Physics Abbreviated Journal Phys. Rev. B Condens. Matter Mater. Phys.  
  Volume 54 Issue 2 Pages 1366-1381  
  Abstract A high sensitivity capacitance torquemeter has been used for a comprehensive investigation of the induced current densities and dynamic relaxation rates in a YBa2Cu3Oxn film with nominal oxygen content varying between xn=6.55 and xn=7.0. The dynamic relaxation rate Q does not extrapolate to zero at T=0 K, indicating the presence of quantum creep. By changing the oxygen content of the film it is possible to investigate the relation between the quantum creep rate Q(0) and the normal-state resistivity pn(0) at low temperature. Although Q(0) increases monotonically with pn, it is found that Q(0) is not proportional to pn(0), in contrast to the predictions of a theory based on dissipative tunneling of collectively pinned single vortices [Blatter et al., Rev. Mod. Phys. 66, 1125 (1994)]. The experimental results imply that in YBa2Cu3O7 quantum creep takes place in a transition regime between Hall tunneling and dissipative tunneling. For lower oxygen contents the quantum creep regime moves towards the dissipative limit. For each oxygen content the characteristic pinning energy Uc(0) at T=0 is obtained by a linear extrapolation to T= 0 K of the T/Q versus T curves. The critical current density jc at T=0 is determined independently by a linear extrapolation of the measured Injs versus T curves. A power-law relation Uc(0)?[jc(0)]p with p? 0.5 is found, indicating single vortex pinning at higher temperatures. This is confirmed by a detailed analysis of the measured current densities and relaxation rates by means of the generalized inversion scheme developed by Schnack et al. [Phys. Rev. B 48, 13 178 (1993)]. For xn? 6.6 at Be= 0.6 T and for xn? 6.7 at Be= 2.0 T the calculated temperature dependence of jc and Uc agrees remarkably well with a model based on three-dimensional single vortex pinning caused by spatial fluctuations in the charge carrier mean free path. At lower oxygen contents and higher magnetic-fields the agreement gradually breaks down due to the increasing importance of thermal fluctuations.  
  Address Montell Polyolefins, Centre Ricerche G. Natta, P. Le P. to G. Donegani 12, 44100 Ferrara, Italy  
  Corporate Author Thesis  
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  Series Volume Series Issue Edition  
  ISSN 01631829 (ISSN) ISBN Medium  
  Area Expedition Conference  
  Notes Cited By (since 1996): 27; Export Date: 17 April 2009; Source: Scopus; CODEN: PRBMD; Language of Original Document: English; Correspondence Address: Van Dalen, A.J.J.; Materials Science Division; Argonne National Laboratory Argonne, IL 60439, United States; References: Mota, A.C., Pollini, A., Visani, P., M Approved no  
  Call Number BT @ osquigui @ Serial 383  
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