Low-temperature magnetic relaxation in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">YBa</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mm

Fruchter, L.; Malozemoff, A. P.; Campbell, I.A.; Sanchez, J.P.; Kończykowski, M.; Griessen, R.; Holtzberg, F.

doi:10.1103/physrevb.43.8709

Cited by 143 publications

(47 citation statements)

References 21 publications

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“…For most superconductors this situation does not occur. In particular even at zero temperature high-T c superconductors exhibit quantum creep, 13 which allows the vortices to relax; for these materials we thus expect a current uniform over the thickness. For further details the reader is referred to the discussion by Brandt.…”

Section: Finding the Currents From The Field H Z : Analytical Formentioning

confidence: 99%

Determination of two-dimensional current patterns in flat superconductors from magneto-optical measurements: An efficient inversion scheme

et al. 1996

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An efficient inversion scheme is given to derive the local currents in a superconductor from the z component of the magnetic field measured above its surface, as is done using magneto-optical indicators. The method works for samples of arbitrary thickness provided that the current vector has only x and y components. Data storage is much lower and convergence much faster than in previously reported schemes. The influence of the distance of observation and of the sample aspect ratio on the measured field H z is investigated. The current calculated from the magneto-optical observation of a real sample ͑a Bi 2 Sr 2 CaCu 2 O 8 single crystal͒ is in good agreement with the value measured directly by means of torque magnetometry.

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Section: Finding the Currents From The Field H Z : Analytical Formentioning

confidence: 99%

Determination of two-dimensional current patterns in flat superconductors from magneto-optical measurements: An efficient inversion scheme

et al. 1996

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“…At low temperature thermally activated creep is expected to vanish linearly with decreasing temperature (R th |T →0 ∼ kT /U c ) but it has been observed in several systems [10] (including high-T c oxides, Chevrel phases, heavy fermions, or organic superconductors), that the relaxation rate does not extrapolate to zero for T → 0 suggesting a decay of the critical state by quantum tunneling [11]. A similar study in iron-based superconductors was still lacking.…”

Section: Introductionmentioning

confidence: 99%

Vortex creep down to 0.3 K in superconducting Fe(Te,Se) single crystals

et al. 2014

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We report on a study of the vortex creep in Fe 1+δ (Te x Se 1−x ) single crystals (x = 0.5 and 0.4) down to 0.28 K (∼T c /50) and up to μ 0 H a = 2T. The relaxation of the current density [J (t)] has been measured during 20 hours and the decay of J (t) can be well described by a J (t) ∝ [ln(t/t 0 )] −1/μ law. We show that the relaxation exponent μ tends towards 0 for T < 2K and μ 0 H a < 0.1T [i.e. J (t) → (t 0 /t) α ] and increases for increasing T and/or H a . Our measurements strongly suggest that the logarithmic creep rate R = −d ln(J )/d ln(t) remains finite at zero temperature (R |T →0 → 2%) and hence that quantum creep plays a dominant role in the relaxation process at low temperature. A maximum is observed in both the temperature and field dependence of R(t = 100s,T ,H a ), which can be associated to a crossover from a single vortex (one-dimensional) to a bundle (three-dimensional) creep regime.

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“…The crossover from quantum creep to thermally activated creep takes place at TϷ6 K, which is in agreement with values reported in the literature. 4,6,12 It is, in principle, possible to use the slope C in the T/Q(T) graphs to identify the pinning regime. For this a value for C is required to evaluate .…”

Section: ͑23͒mentioning

confidence: 99%

Quantum creep and pinning properties of oxygen-deficientYBa2Cu3

Bruynseraede¹,

Griessen²,

Libbrecht

et al. 1996

Phys. Rev. B

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A high sensitivity capacitance torquemeter has been used for a comprehensive investigation of the induced current densities and dynamic relaxation rates in a YBa 2 Cu 3 O x n film with nominal oxygen content varying between x n ϭ6.55 and x n ϭ7.0. The dynamic relaxation rate Q does not extrapolate to zero at Tϭ0 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 n (0) at low temperature. Although Q(0) increases monotonically with n , it is found that Q(0) is not proportional to n (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 ͑1994͔͒. The experimental results imply that in YBa 2 Cu 3 O 7 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 U c (0) at Tϭ0 is obtained by a linear extrapolation to Tϭ 0 K of the T/Q versus T curves. The critical current density j c at Tϭ0 is determined independently by a linear extrapolation of the measured lnj s versus T curves. A power-law relation U c (0)ϰ͓ j c (0)͔ p with pϷ 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 ͑1993͔͒. For x n у 6.6 at B e ϭ 0.6 T and for x n у 6.7 at B e ϭ 2.0 T the calculated temperature dependence of j c and U c agrees remarkably well with a model based on threedimensional 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. ͓S0163-1829͑96͒04925-9͔

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Low-temperature magnetic relaxation inYBa2Cu3

Cited by 143 publications

References 21 publications

Determination of two-dimensional current patterns in flat superconductors from magneto-optical measurements: An efficient inversion scheme

Determination of two-dimensional current patterns in flat superconductors from magneto-optical measurements: An efficient inversion scheme

Vortex creep down to 0.3 K in superconducting Fe(Te,Se) single crystals

Quantum creep and pinning properties of oxygen-deficientYBa2Cu3

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