Extension of the time window for investigation of relaxation effects in high-Tc superconductors

Jirsa, M.; Půst, L.; Schnack, H.G.; Griessen, R.

doi:10.1016/0921-4534(93)90426-q

Cited by 106 publications

(54 citation statements)

References 26 publications

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“…It has been demonstrated that the dependence of the hysteresis amplitude on the sweep rate contains basically the same information of the time dependence of the magnetization during relaxation, in particular, the higher is the sweep rate, the shorter is the effective "observing time" in the m(t) curve. 86,87 The results are shown in Fig. 10, along with the curve acquired by the SQUID and the values (full points) extracted from the m(t) curves, obtained at different fields, considering t = 5000 s. Regarding the measurement performed with the SQUID, one can assumeḢ = 0 since any variation of H during the acquisition can be neglected.…”

Section: B Vortex Dynamics Propertiesmentioning

confidence: 99%

Temperature and time scaling of the peak-effect vortex configuration in FeTe0.7Se0.3

et al. 2012

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An extensive study of the magnetic properties of FeTe 0.7 Se 0.3 crystals in the superconducting state is presented. We show that weak collective pinning, originating from spatial variations of the charge carrier mean free path (δl pinning), rules in this superconductor. Our results are compatible with the nanoscale phase separation observed on this compound and indicate that in spite of the chemical inhomogeneity, spatial fluctuations of the critical temperature are not important for pinning. A power-law dependence of the magnetization vs time, generally interpreted as the signature of a single-vortex creep regime, is observed in magnetic fields up to 8 T. For magnetic fields applied along the c axis of the crystal, the magnetization curves exhibit a clear peak effect whose position shifts when varying the temperature, following the same dependence as observed in YBa 2 Cu 3 O 7−δ . The time and temperature dependence of the peak position has been investigated. We observe that the occurrence of the peak at a given magnetic field determines a specific vortex configuration that is independent on the temperature. This result indicates that the influence of the temperature on the vortex-vortex and vortex-defect interactions leading to the peak effect in FeTe 0.7 Se 0.3 is negligible in the explored range of temperatures.

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Section: B Vortex Dynamics Propertiesmentioning

confidence: 99%

Temperature and time scaling of the peak-effect vortex configuration in FeTe0.7Se0.3

et al. 2012

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“…It has been proven that measurements of the dynamic magnetic moment are equivalent to the normal relaxation measurements, in which the magnetic moment is recorded as a function of time at fixed temperature and magnetic field, when studying the relaxation of HTS. 46,47 Therefore, by measuring the vertical levitation force F z versus z at different frequencies with which the PM approaches and recedes away from the HTS, one can study the relaxation of the force as well as the current density in the HTS.…”

Section: Force Creepmentioning

confidence: 99%

Calculation of the hysteretic force between a superconductor and a magnet

Qin

Liu

et al. 2002

Phys. Rev. B

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The magnetic levitation forces exerted on a high-temperature superconducting ͑HTS͒ disk by a cylindrical permanent magnet ͑PM͒ are calculated from first principles for superconductors with finite thickness. The current j( ,z) and field B( ,z) profiles in the HTS in the nonuniform magnetic field generated by the PM are derived. The levitation force depends nonlinearly on the critical current density j c and on the thickness of the HTS. The flux creep is described by a current-voltage law E( j)ϭE c ( j/ j c ) n , from which we show that the levitation force depends on the speed at which the PM approaches or recedes from the HTS, which accounts for the experimentally observed force creep phenomenon. The stiffness of the system is derived by calculating minor force loops. The numerical results reproduce many of the features observed in experiments.

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“…Self-heating begins to play a minor role at T b ϭ0.1 K where For the thin films we therefore performed dynamic relaxation experiments thus avoiding magnetic-field overshoot when stopping a field sweep, which has great effect on the conventional relaxation process for samples with small penetration field B p . 26 For the single crystals with high B p the overshoot effect is small and here we performed conventional relaxation measurements to reduce self-heating ͑except for the Pr 1.85 Ce 0.15 CuO 4ϩ␦ single crystal with T c ϭ12.1 K which only supports low j s ).…”

Section: A Self-heating Due To Vortex Motionmentioning

confidence: 99%

Temperature and magnetic-field dependence of quantum creep in various high-Tcsuperconductors

et al. 1999

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To investigate the quantum tunneling of almost macroscopic vortex segments we measured the normalized relaxation rate Q of superconducting currents for various high-T c superconductors ͑HTS's͒ down to 100 mK in magnetic fields up to 7 T. At fields below Х0.5 T, Q is essentially independent of T in the temperature regime between thermally activated and quantum motion as theoretically expected. However, at higher fields, we find an unexpected linear T dependence of Q persisting down to the lowest temperatures in all investigated samples. Since these compounds were chosen to represent the distinct classes of dirty and clean HTS's, the extrapolated Q(Tϭ0) values are used to discuss the theoretical models for quantum creep in the clean and dirty limits. Based on this discussion we propose a semiempirical interpolation formula for Q(Tϭ0) which is also valid for compounds in between the dirty and clean limits. ͓S0163-1829͑99͒00806-1͔

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Extension of the time window for investigation of relaxation effects in high-Tc superconductors

Cited by 106 publications

References 26 publications

Temperature and time scaling of the peak-effect vortex configuration in FeTe0.7Se0.3

Temperature and time scaling of the peak-effect vortex configuration in FeTe0.7Se0.3

Calculation of the hysteretic force between a superconductor and a magnet

Temperature and magnetic-field dependence of quantum creep in various high-Tcsuperconductors

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