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Pasquini, G.; Civale, L.; Lanza, H.; Nieva, G.

doi:10.1103/physrevb.65.214517

Cited by 16 publications

(23 citation statements)

References 31 publications

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“…The associated Meissner-type, nondissipative currents serve to screen the film and restrict the loss ͑ max Љ ͒ to levels below that obtained in a strictly Bean-type critical state. Qualitatively similar reductions in ͑ max Љ ͒ were observed in low ac fields by Pasquini et al 58 ͑and references therein͒ in thin films of the high-T c superconductor YBa 2 Cu 3 O 7 ; these researchers successfully analyzed their findings in terms of a high-screening, lowdissipation Campbell regime at low amplitudes. Also, Herzog et al 59 observed an amplitude dependence similar to that in Fig.…”

Section: Nonequilibrium Critical-state Propertiessupporting

confidence: 65%

Robust superconductivity in quantum-confined Pb: Equilibrium and irreversible superconductive properties

2006

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Strong quantum size effects enable the formation of crystalline Pb films that are atomically flat on a macroscopic length scale. The superconducting properties of 5-18-monolayer-͑ML͒ thick Pb films were investigated in a superconducting quantum interference device ͑SQUID͒ magnetometer using combined ac and dc methods. Even the thinnest films ͑5 ML͒ are extraordinarily robust type-II superconductors. Despite the extreme two-dimensional geometry, the thermodynamic parameters T c and upper critical field H c2 are primarily controlled by the physical boundary conditions of the film and show no evidence for disorder-driven or fluctuation-driven quenching of superconductivity. A magnetically hard critical state is established as a consequence of vortex trapping by quantum growth defects.

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Section: Nonequilibrium Critical-state Propertiessupporting

confidence: 65%

Robust superconductivity in quantum-confined Pb: Equilibrium and irreversible superconductive properties

2006

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“…It is also worth noticing that the extension of the Campbell regime for the patterned sample is clearly larger than for the reference film. Moreover, this result is quantitatively consistent with the predicted 14 proportionality between h * and J. Indeed, the h * ͑T͒ boundary for the plain film multiplied by a factor J͑antidots͒ / J͑plain film͒, represented by filled squares in Fig.…”

Section: Boundary Of the Campbell Regimesupporting

confidence: 87%

Crossover from intravalley to intervalley vortex motion in type-II superconductors with a periodic pinning array

et al. 2006

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We have determined the transition from intravalley vortex motion ͑Campbell regime͒ to intervalley motion ͑critical state regime͒ in Pb thin films with and without a square array of holes ͑antidots͒ by means of ac susceptibility ͑T , H͒ measurements. The Campbell regime is characterized by a maximum dissipation max Љ dependent on the ac excitation h but nearly temperature independent. In contrast, in the critical state regime, the height of the dissipation peak remains constant, whereas its position shifts to lower temperatures with increasing h. We introduce an alternative way for determining the temperature dependence of the ac onset of the Bean critical state by analyzing the critical current density J͑T͒ extracted from the Ј͑T͒ data at several h. We demonstrate that the presence of a periodic pinning array strongly affects the extension of the crossover area in the h − T diagram between these regimes. We show that this effect can be ascribed to the lower dispersion of the pinning energy together with the higher topological order for the antidot sample.

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“…These small anisotropy values are in good agreement with those reported in other works 14,22,23 , obtained by other methods. The scaling fails when the field direction approaches the ab planes, similarly to that observed in HTS cuprates 9,10 , where this fact is adscribed to the modulation of the superconducting parameter with atomic layers. Intrinsic pinning has been observed also in Codoped BaFe 2 As 2 films at low T 11 .…”

Section: Resultsmentioning

confidence: 51%

“…The efficiency of twin boundaries as pinning centers has been extensively probed in YBCO crystals 6 , and the correlated nature of this pinning has been evidenced by measuring the angular dependence of the transport properties: a sharp peak in the resistivity together with a change in the universality class of the glass to liquid transition when the magnetic field is applied at small angles away from the direction of the correlated defects have been observed 7 . By magnetization 8,9 and ac susceptibility measurements 10 , it has been shown that correlated defects modify the expected intrinsic angular dependence (due to the material anisotropy) over a larger angular region. This fact has been explained in terms of formation of vortex staircases 9,12 , with vortex segments aligned with the defects, but the mean vortex direction following that of the applied magnetic field.…”

Section: Introductionmentioning

confidence: 99%