References of "Colauto, F"
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See detailControllable morphology of flux avalanches in microstructured superconductors
Motta, M.; Colauto, F.; Vestgarden, J.I. et al

in Physical Review. B : Condensed Matter (2014)

The morphology of abrupt bursts of magnetic flux into superconducting films with engineered periodic pinning centers (antidots) has been investigated. Guided flux avalanches of thermomagnetic origin ... [more ▼]

The morphology of abrupt bursts of magnetic flux into superconducting films with engineered periodic pinning centers (antidots) has been investigated. Guided flux avalanches of thermomagnetic origin develop a tree-like structure, with the main trunk perpendicular to the borders of the sample, while secondary branches follow well-defi ned directions determined by the geometrical details of the underlying periodic pinning landscape. Strikingly, we demonstrate that in a superconductor with relatively weak random pinning, the morphology of such flux avalanches can be fully controlled by proper combinations of lattice symmetry and antidot geometry. Moreover, the resulting flux patterns can be reproduced, to the fi nest details, by simulations based on a phenomenological thermomagnetic model. In turn, this model can be used to predict such complex structures and to estimate physical variables of more di fficult experimental access, such as the local values of temperature and electric fi eld. [less ▲]

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See detailEnhanced pinning in superconducting thin films with graded pinning landscapes
Motta, M.; Colauto, F.; Ortiz, W.A. et al

in Applied Physics Letters (2013), 102

A graded distribution of antidots in superconducting a-Mo79Ge21 thin films has been investigated by magnetization and magneto-optical imaging measurements. The pinning landscape has maximum density at the ... [more ▼]

A graded distribution of antidots in superconducting a-Mo79Ge21 thin films has been investigated by magnetization and magneto-optical imaging measurements. The pinning landscape has maximum density at the sample border, decreasing linearly towards the center. Its overall performance is noticeably superior than that for a sample with uniformly distributed antidots: For high temperatures and low fields, the critical current is enhanced, whereas the region of thermomagnetic instabilities in the field-temperature diagram is significantly suppressed. These findings confirm the relevance of graded landscapes on the enhancement of pinning efficiency, as recently predicted by Misko and Nori [Phys. Rev. B 85, 184506 (2012)]. [less ▲]

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See detailMorphology of Flux Avalanches in Patterned Superconducting Films
Zadorosny, R; Colauto, F; Motta, M et al

in Journal of Superconductivity & Novel Magnetism (2013), 26

It is well known that under certain circumstances, magnetic fields applied perpendicularly to the plane of superconducting films can trigger flux avalanches. In such cases the penetration has a tree-like ... [more ▼]

It is well known that under certain circumstances, magnetic fields applied perpendicularly to the plane of superconducting films can trigger flux avalanches. In such cases the penetration has a tree-like profile. However, in samples where a regular array of antidots, ADs, is present, the avalanches follow the rows of ADs as if they were guiding lines for the abrupt penetration. In this work we used the magneto-optical imaging technique to study the morphology of flux avalanches in two Nb films with a square lattice of square ADs, each one with a different lateral size, and a plain film for reference. We show that the morphology of the flux avalanches is greatly influenced by the size of the interstitial region. [less ▲]

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See detailFlux avalanches triggered by AC magnetic fields in superconducting thin films
Motta, M; Colauto, F; Johansen, TH et al

in Physica C (2012), 479

Flux avalanches are known to occur as a consequence of thermomagnetic instabilities. Some of their fingerprints are jumps in magnetization curves, or a paramagnetic reentrance in AC susceptibility ... [more ▼]

Flux avalanches are known to occur as a consequence of thermomagnetic instabilities. Some of their fingerprints are jumps in magnetization curves, or a paramagnetic reentrance in AC susceptibility measurements. In this work we have studied flux avalanches triggered by an AC field cycle by means of AC susceptibility and residual magnetization after an applied AC field measured as a function of an AC excitation field (h). These measurements allow comparing both results with magneto-optical imaging carried out in similar conditions. The results show a correspondence for the onset of the avalanche activity, as well as between the residual magnetic moment and the mean gray value calculated from the magneto-optical images in the remanent state. [less ▲]

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See detailVisualizing the ac magnetic susceptibility of superconducting films via magneto-optical imaging
Motta, M.; Colauto, F.; Zadorosny, R. et al

in Physical Review. B, Condensed Matter and Materials Physics (2011), 84(21), 214529

We have established a link between the global ac response and the local flux distribution of superconducting films by combining magnetic ac susceptibility, dc magnetization, and magneto-optical ... [more ▼]

We have established a link between the global ac response and the local flux distribution of superconducting films by combining magnetic ac susceptibility, dc magnetization, and magneto-optical measurements. The investigated samples are three Nb films: a plain specimen, used as a reference sample, and other two films patterned with square arrays of antidots. At low temperatures and small ac amplitudes of the excitation field, the Meissner screening prevents penetration of flux into the sample. Above a certain ac drive threshold, flux avalanches are triggered during the first cycle of the ac excitation. The subsequent periodic removal, inversion, and rise of flux occurs essentially through the already-created dendrites, giving rise to an ac susceptibility signal weakly dependent on the applied field. The intradendrite flux oscillation is followed, at higher values of the excitation field, by a more drastic process consisting of creation of new dendrites and antidendrites. In this more invasive regime, the ac susceptibility shows a clear field dependence. At higher temperatures a smooth penetration occurs, and the flux profile is characteristic of a critical state. We have also shown that the regime dominated by vortex avalanches can be reliably identified by ac susceptibility measurements. [less ▲]

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