References of "Physica C: Superconductivity"
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See detailDirect visualization of the vortex distributions in a superconducting film with a Penrose array of magnetic pinning centers: Symmetry induced giant vortex state
Kramer, R. B. G.; Silhanek, Alejandro ULg; Van de Vondel, J. et al

in Physica C: Superconductivity (2010), 470(19), 758-761

Using scanning Hall probe microscopy a direct visualization of the flux distribution in a Pb film covering a fivefold Penrose array of Co dots is obtained. We demonstrate that stable vortex configurations ... [more ▼]

Using scanning Hall probe microscopy a direct visualization of the flux distribution in a Pb film covering a fivefold Penrose array of Co dots is obtained. We demonstrate that stable vortex configurations can be found for fields H similar to 0.8H(1), H(1) and 1.6H(1), where H(1) corresponds to one flux quantum per pinning site. The vortex pattern at 0.8H(1) corresponds to one vacancy in one of the vertices of the thin tiles whereas at 1.6H(1) the vortex structure can be associated with one interstitial vortex inside each thick tile. Strikingly, for H = 1.6H(1) interstitial and pinned vortices arrange themselves in ring-like structures ("vortex corrals") which favor the formation of a giant vortex state at their center. (C) 2010 Published by Elsevier B.V. [less ▲]

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See detailPinning effects on the vortex critical velocity in type-II superconducting thin films
Leo, A.; Grimaldi, G.; Nigro, A. et al

in Physica C: Superconductivity (2010), 470(19), 904-906

We study the influence of artificial pinning centers on the vortex critical velocity in Al thin films deposited on top of a periodic array of Permalloy (FeNi) square rings. We demonstrate that the field ... [more ▼]

We study the influence of artificial pinning centers on the vortex critical velocity in Al thin films deposited on top of a periodic array of Permalloy (FeNi) square rings. We demonstrate that the field dependence of the flux flow velocity strongly depends on the particular magnetic state of the rings. In particular, we find that, even when the rings are in a flux closure state, i.e. with little stray field, the vortex critical velocity shows a non-monotonic magnetic field dependence. This behaviour is in sharp contrast with the results obtained in a reference plain film, with no rings underneath. A comparison with the intrinsic strong pinning Nb films previously studied, suggests an interpretation in terms of a channel-like motion of vortices, here induced by the artificial pinning structure. (C) 2010 Elsevier B.V. All rights reserved. [less ▲]

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See detailField polarity dependent superconducting properties in a superconductor/ferromagnet hybrid with in-plane magnetic moment
Gillijns, W.; Godts, F.; Ataklti, G. W. et al

in Physica C: Superconductivity (2010), 470(19), 880-882

The transport properties of an Al type-II superconducting thin film covering a Py plain film with a rectangular array of triangular holes are investigated. We show that, although the magnetization of the ... [more ▼]

The transport properties of an Al type-II superconducting thin film covering a Py plain film with a rectangular array of triangular holes are investigated. We show that, although the magnetization of the Py lies in the plane of the structure, both the critical temperature and the critical current are asymmetric with respect to the polarity of the external field, which is applied perpendicularly to the structure. The asymmetric nucleation can be explained in terms of field compensation effects between internal and external magnetic fields, whereas the presence of vortex-antivortex pairs are responsible for the observed features in the critical current. (C) 2010 Elsevier B.V. All rights reserved. [less ▲]

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See detailProbing the discrete motion of vortices with rf excitations
Van de Vondel, J.; Silhanek, Alejandro ULg; Moshchalkov, V. V. et al

in Physica C: Superconductivity (2010), 470(19), 857-859

In this work we present experimental results on the rectification of vortices in a superconductor/ferromagnet system under a high frequency drive. The two-dimensional pinning landscape, induced by the ... [more ▼]

In this work we present experimental results on the rectification of vortices in a superconductor/ferromagnet system under a high frequency drive. The two-dimensional pinning landscape, induced by the stray fields of the ferromagnetic template, has no intrinsic asymmetry. Nevertheless, an asymmetric potential is artificially induced by an applied dc bias. The experimental results unambiguously show a biased, discrete motion of the vortices in the periodic potential at frequencies above 10 MHz. This synchronized motion is very sensitive to the external applied field. Increasing temperature leads to a reduction of the pinning potential, which in turn results in a lower ac power needed to drive the vortex lattice. (C) 2010 Elsevier B.V. All rights reserved. [less ▲]

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See detailFreezing vortex rivers
Silhanek, Alejandro ULg; Kramer, R. G. B.; Van de Vondel, J. et al

in Physica C: Superconductivity (2010), 470(19), 726-729

We demonstrate experimentally and theoretically that the dissipative state at high current densities of superconducting samples with a periodic array of holes consist of flux rivers resulting from a short ... [more ▼]

We demonstrate experimentally and theoretically that the dissipative state at high current densities of superconducting samples with a periodic array of holes consist of flux rivers resulting from a short range attractive interaction between vortices. This dynamically induced vortex-vortex attraction results from the migration of quasiparticles out of the vortex core. We have directly visualized the formation of vortex chains by scanning Hall microscopy after freezing the dynamic state by a field cooling procedure at constant bias current. Similar experiments carried out in a sample without holes show no hint of flux river formation. (C) 2010 Elsevier B.V. All rights reserved. [less ▲]

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See detailField polarity dependent nucleation of superconductivity in quasi-one-dimensional magnetic templates
Ataklti, G. W.; Silhanek, Alejandro ULg; Van de Vondel, J. et al

in Physica C: Superconductivity (2010), 470(19), 860-862

We investigate the nucleation of superconductivity in an Al/Al(2)O(3)/Py trilayer system by electrical transport measurements. Magnetic force microscopy images taken at room temperature show that the 0.7 ... [more ▼]

We investigate the nucleation of superconductivity in an Al/Al(2)O(3)/Py trilayer system by electrical transport measurements. Magnetic force microscopy images taken at room temperature show that the 0.7 mu m thick Py-film form stripes of magnetic domains with alternating out-of-plane stray field. After applying a strong out of plane magnetic field H the superconductor/normal phase boundary becomes asymmetric with respect to H = 0. This lack of field polarity symmetry results from the unbalanced size distribution of domains with opposite polarity. (C) 2010 Elsevier B.V. All rights reserved. [less ▲]

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See detailMagnetic tunable confinement of the superconducting condensate in superconductor/ferromagnet hybrids
Aladyshkin, A Yu; Gillijns, W.; Silhanek, Alejandro ULg et al

in Physica C: Superconductivity (2008), 468(7-10), 737-740

The effect of a nonuniform magnetic field induced by a ferromagnet on the magnetoresistance of thin-film superconductor/ferromagnet hybrid structures was investigated experimentally. Two different ... [more ▼]

The effect of a nonuniform magnetic field induced by a ferromagnet on the magnetoresistance of thin-film superconductor/ferromagnet hybrid structures was investigated experimentally. Two different magnetic textures with out-of-plane magnetization were considered: a plain ferromagnetic film with bubble domains and a regular array of ferromagnetic dots. The stray fields of the structures are able to affect the spatial profile of the superconducting condensate, leading to a modification of the dependence of the critical temperature T-c on an external magnetic field H. We showed how the standard linear T-c(H) dependence with a single maximum at H = 0 can be continuously transformed into so-called reentrant phase boundary with two T-c peaks. We demonstrated that both domain-wall superconductivity and field-induced superconductivity are different manifestations of the magnetic confinement effect in various magnetic patterns. (C) 2008 Elsevier B.V. All rights reserved. [less ▲]

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See detailPhase slips in mesoscopic superconducting triangles
Schildermans, N.; Salenbien, R.; Silhanek, Alejandro ULg et al

in Physica C: Superconductivity (2008), 468(7-10), 757-760

Voltage-current (V(I)) characteristics are investigated in the superconducting state of an equilateral triangle of 2.2 mu m(2) area. Several steps in the V(I) curves indicate the presence of phase slip ... [more ▼]

Voltage-current (V(I)) characteristics are investigated in the superconducting state of an equilateral triangle of 2.2 mu m(2) area. Several steps in the V(I) curves indicate the presence of phase slip centers in the triangle. The field dependence of these steps follows the Little-Parks oscillations of the phase boundary, associated with the change of vorticity. The influence of the contacts manifests itself as an excess voltage and a negative differential resistance. In addition we show that the position of the current contacts modify the superconducting phase boundary measurements. (C) 2008 Elsevier B.V. All rights reserved. [less ▲]

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See detailRectification effects in superconductors with magnetic pinning centers
Silhanek, Alejandro ULg; Verellen, N.; Metlushko, V. et al

in Physica C: Superconductivity (2008), 468(7-10), 563-567

We investigate the dynamics and pinning properties of vortices in superconducting At films deposited on top of a close-packed array of Py microsized. loops by electrical transport measurements. The ... [more ▼]

We investigate the dynamics and pinning properties of vortices in superconducting At films deposited on top of a close-packed array of Py microsized. loops by electrical transport measurements. The micromagnets have an in-plane magnetic moment that can be set in different magnetic states by applying an external field parallel to the plane of the pattern. When the loops are set in the magnetic vortex-state, for which the stray field is the smallest, a weaker pinning in comparison with the polarized states (i.e. strong stray field) is observed. In addition, a clear influence of the chosen magnetic state of the Py rings on the dynamics of the vortex motion under an ac-excitations is obtained. When the magnetic elements are in the as-grown state a rectification signal which reverses sign when the field changes polarity is observed. In contrast to that, when the array of loops is magnetized the observed rectification effect is independent of the field polarity and can be reversed by reorienting the magnetization of the micromagnets. (c) 2008 Elsevier B.V. All rights reserved. [less ▲]

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See detailEnhanced vortex trapping by a composite antidot lattice in a superconducting Pb film
Silhanek, Alejandro ULg; Van Look, L.; Jonckheere, R. et al

in Physica C: Superconductivity (2007), 460

Using electrical transport measurements, we study a composite antidot lattice consisting of two interpenetrating antidot square arrays with a different antidot size and the same lattice period. We show ... [more ▼]

Using electrical transport measurements, we study a composite antidot lattice consisting of two interpenetrating antidot square arrays with a different antidot size and the same lattice period. We show that placing an additional small antidot in the unit cell of the array a higher number of flux quanta per unit cell can be trapped inside the antidots, compared to a reference antidot film without the additional small antidots. As a consequence, the field range in which an enhanced critical current is observed is considerably expanded. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailField induced metastabilities in U(Ru0.96Rh0.04)(2)Si-2
Silhanek, Alejandro ULg; Jaime, M.; Harrison, N. et al

in Physica C: Superconductivity (2007), 460(Part 1), 682-683

U(Ru0.96Rh0.04)(2)Si-2 is an anisotropic itinerant 5f heavy electron system which exhibits a single field induced magnetic phase concealing a quantum critical point. We show that the boundary of this ... [more ▼]

U(Ru0.96Rh0.04)(2)Si-2 is an anisotropic itinerant 5f heavy electron system which exhibits a single field induced magnetic phase concealing a quantum critical point. We show that the boundary of this phase corresponds to a first order transition as revealed by (1) a large and symmetric specific heat anomaly, (2) an asymmetric magnetocaloric effect on entering and exiting this phase, and (3) a clear history and time-dependent specific heat. We explore the thermodynamic similarities with the mixed valence compound YbInCu4 and show that the out-of-equilibrium properties are analogous to those depicted by the critical state model for hard superconductors. (C) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailAnisotropic avalanches and flux penetration in patterned superconductors
Gheorghe, D. G.; Menghini, M.; Wijngaarden, R. J. et al

in Physica C: Superconductivity (2006), 437-38

Both for a fundamental understanding of the flux penetration process and for technical applications, the role of artificial pinning sites (such as antidots) in superconductors generates a lot of interest ... [more ▼]

Both for a fundamental understanding of the flux penetration process and for technical applications, the role of artificial pinning sites (such as antidots) in superconductors generates a lot of interest. We perform magneto-optical imaging experiments on type-II Pb thin films patterned with square arrays of square antidots and square arrays of rectangular antidots and blind holes. We demonstrate that a square lattice of rectangular antidots can lead to similar anisotropy in flux penetration and critical current as a rectangular lattice of square antidots. In addition we show how thermo-magnetic avalanches can be guided-and hence to a certain extend controlled-by such holes. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailAc response of Pb thin films with a periodic pinning potential
Silhanek, Alejandro ULg; Raedts, S.; Moshchalkov, V. V.

in Physica C: Superconductivity (2004), 404(1-4), 345-349

We have studied the dynamic response of Pb thin films with a square array of antidots by means of ac susceptibility chi(T, H) measurements. For low amplitudes h of the ac excitation, the field dependence ... [more ▼]

We have studied the dynamic response of Pb thin films with a square array of antidots by means of ac susceptibility chi(T, H) measurements. For low amplitudes h of the ac excitation, the field dependence of the ac susceptibility exhibits a series of distinctive features associated with the presence of different dynamic regimes. For fields below a certain characteristic field H-s, vortices strongly pinned by the antidots perform an oscillatory movement inside the pinning potential induced by the external ac drive. For fields between H-s and H-p, interstitial vortices, performing an intra-valley motion in the weak potential wells produced by the repulsive interaction of their pinned neighbors, dominate the ac response. For H-p < H < H-t, the interstitial vortices are driven out of their pinning sites while vortices in the antidots remain trapped. For higher fields all vortices are set in motion and a critical state develops. We show that the characteristic h-independent field H-s allows one to clearly identify the maximum number of flux quanta per hole. Unlike H-s, the fields H-p and H-t, signaling the onset of motion of interstitial vortices and vortices trapped by the antidots, respectively, strongly depend on h. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailAC susceptibility of superconducting films with a periodic pinning array
Silhanek, Alejandro ULg; Raedts, S.; Lange, M. et al

in Physica C: Superconductivity (2004), 408

We use AC-susceptibility measurements to study the dynamic response of vortices in a Pb thin film with a periodic array of antidots. In the linear regime, from the field dependence of the AC-penetration ... [more ▼]

We use AC-susceptibility measurements to study the dynamic response of vortices in a Pb thin film with a periodic array of antidots. In the linear regime, from the field dependence of the AC-penetration depth lambda we determine the curvature of the pinning potential well alpha for different matching fields. For applied fields H below the first matching field H-1, alpha reaches its highest value due to the strong vortex localization at the pinning sites. For H-1 < H < H-2, the metallic-like behavior of interstitial vortices gives rise to a reduction of alpha and a further decrease of the pinning strength is observed for H-2 < H < H-3. However, for H-3 < H < H-4, a reentrance in the pinning strength appears, due to a specific configuration of the flux line lattice which strongly restricts the mobility of vortices. [less ▲]

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See detailFlux pinning properties of holes and blind holes arranged periodically in a superconductor
Raedts, S.; Silhanek, Alejandro ULg; Van Bael, M. J. et al

in Physica C: Superconductivity (2004), 404(1-4), 298-301

We investigate the dynamic response of a vortex lattice in nanostructured superconducting Pb films by means of ac-magnetization measurements. We compare the flux pinning properties of superconducting Pb ... [more ▼]

We investigate the dynamic response of a vortex lattice in nanostructured superconducting Pb films by means of ac-magnetization measurements. We compare the flux pinning properties of superconducting Pb films with arrays of fully perforated holes (antidots) and partially drilled holes (blind holes). Our results show that an array of blind holes, characterized by a thin superconducting bottom layer, gives rise to a less efficient pinning potential than an array of antidots. On top of that, a lower number of flux quanta trapped per pinning site (the saturation number), is observed for the blind hole array. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailIn-plane anisotropic vortex motion induced by a square array of antidots
Silhanek, Alejandro ULg; Van Look, L.; Raedts, S. et al

in Physica C: Superconductivity (2004), 404(1-4), 340-344

We report on electro-transport measurements on a Pb thin film with a square array of antidots, for the whole angular range of in-plane current orientations. We demonstrate that the interaction of a moving ... [more ▼]

We report on electro-transport measurements on a Pb thin film with a square array of antidots, for the whole angular range of in-plane current orientations. We demonstrate that the interaction of a moving flux line lattice with a periodic pinning potential, breaks the rotational symmetry and induces a guided vortex motion along the principal symmetry orientations of the pinning array. As a consequence, we found that for orientations different than the symmetry directions, the vortex velocity is not aligned with the Lorentz force. We show that this anisotropic vortex motion is temperature dependent and progressively fades out when approaching the normal state. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailMagneto-transport study of nb-doped Bi/Pb2223 superconductor
Pekala, Marek; Mucha, Jan ULg; Cloots, Rudi ULg et al

in Physica C: Superconductivity (2003), 387(1-2), 191-197

The magneto-transport properties of Bi1.5Pb0.4Nb0.1Sr2Ca2Cu3O10-x polycrystalline, superconducting ceramic are reported. The material was found to be chemically homogeneous and partially textured. The ... [more ▼]

The magneto-transport properties of Bi1.5Pb0.4Nb0.1Sr2Ca2Cu3O10-x polycrystalline, superconducting ceramic are reported. The material was found to be chemically homogeneous and partially textured. The mixed state properties were investigated by measuring the electrical resistivity, longitudinal and transverse (Nernst effect) thermoelectric power, and thermal conductivity. The magnetization and AC susceptibility measurements were also performed. The variation of these characteristics for magnetic fields up to 5 T are discussed and compared to those of the zero field case. The transport entropy and thermal Hall angle are extracted and quantitatively compared to previously reported data of closely related systems. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailMagnetic and transport measurements on melt-textured DyBCO single domains
Vanderbemden, Philippe ULg; Misson, Vincent; Ausloos, Marcel ULg et al

in Physica C: Superconductivity (2002), 372(Part 2), 1225-1228

In this communication we report critical current measurements of melt processed DyBa2Cu3O7-x samples determined by several measuring techniques. First the material was characterized by AC susceptibility ... [more ▼]

In this communication we report critical current measurements of melt processed DyBa2Cu3O7-x samples determined by several measuring techniques. First the material was characterized by AC susceptibility and DC magnetization. The results are characteristic of good quality melt-processed (RE)BCO material with T-c = 89 K and Jc(77 K, 1 T) = 10^4 A/cm^2. Next, pulsed currents were used in order to determine both I-V curves and transport critical currents. The origin of the discrepancy between transport and magnetic data has been discussed. The results point out significant local variations of the critical current density throughout the single domain. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailYBa2Cu3O7 tapes prepared by sol-gel deposition techniques: microstructure and structural characterizations
Marguillier, David ULg; Cloots, Rudi ULg; Rulmont, André ULg et al

in Physica C: Superconductivity (2002), 372(Part 2), 715-718

We report on the preparation conditions of YBa2Cu3O7 polycrystalline superconducting tapes by a sol-gel deposition technique. We present some discussion on the compatibility between the nature of the ... [more ▼]

We report on the preparation conditions of YBa2Cu3O7 polycrystalline superconducting tapes by a sol-gel deposition technique. We present some discussion on the compatibility between the nature of the substrate, the use of a buffer layer, and the conditions used to prepare appropriate superconducting YBa2Cu3O7,, materials. We report also on the microstructural characterizations performed in order to evaluate the crystallites size, degree of orientation and connectivity. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailIntragranular and intergranular behaviour of multifilamentary Bi-2223/Ag tapes
Fagnard, Jean-François ULg; Vanderbemden, Philippe ULg; Crate, David et al

in Physica C: Superconductivity (2002), 372(Part 2), 970-973

This communication aims at reporting the superconducting properties of Bi-2223/Ag tapes determined by using various measuring techniques. First. the original samples have been characterized by electrical ... [more ▼]

This communication aims at reporting the superconducting properties of Bi-2223/Ag tapes determined by using various measuring techniques. First. the original samples have been characterized by electrical resistance, AC susceptibility. and DC magnetization. The transport (intergranular) critical Current vs. magnetic field was also determined at T = 77 K using pulsed currents up to 40 A. Next. the same combination of experiments as performed oil bent tapes in order to bring out relevant information concerning the strength of the intergranular coupling. The results show that intergranular and intragranular currents differ by at least one order of magnitude, Finally, additional magnetic measurements were carried out in order to determine the anisotropy ratio Jc(ab)/Jc(c), which was found to lie around 30. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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