References of "Silhanek, Alejandro"
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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 detailVoltage rectification effects in mesoscopic superconducting triangles: Experiment and modeling
Schildermans, N.; Kolton, A. B.; Salenbien, R. et al

in Physical Review. B : Condensed Matter (2007), 76(22),

The interaction of externally applied currents with persistent currents induced by magnetic field in a mesoscopic triangle is investigated. As a consequence of the superposition of these currents, clear ... [more ▼]

The interaction of externally applied currents with persistent currents induced by magnetic field in a mesoscopic triangle is investigated. As a consequence of the superposition of these currents, clear voltage rectification effects are observed. We demonstrate that the amplitude of the rectified signal strongly depends on the configurations of the current leads with the lowest signal obtained when the contacts are aligned along a median of the triangle. When the contacts are aligned off centered compared to the geometrical center, the voltage response shows oscillations as a function of the applied field, whose sign can be controlled by shifting the contacts. These results are in full agreement with theoretical predictions for an analogous system consisting of a closed loop with a finite number of identical Josephson junctions. [less ▲]

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See detailDipole-induced vortex ratchets in superconducting films with arrays of micromagnets
de Souza Silva, C. C.; Silhanek, Alejandro ULg; Van de Vondel, J. et al

in Physical Review Letters (2007), 98(11),

We investigate the transport properties of superconducting films with periodic arrays of in-plane magnetized micromagnets. Two different magnetic textures are studied: a square array of magnetic bars and ... [more ▼]

We investigate the transport properties of superconducting films with periodic arrays of in-plane magnetized micromagnets. Two different magnetic textures are studied: a square array of magnetic bars and a close-packed array of triangular microrings. As confirmed by magnetic force microscopy imaging, the magnetic state of both systems can be adjusted to produce arrays of almost pointlike magnetic dipoles. By carrying out transport measurements with ac drive, we observed experimentally a recently predicted ratchet effect induced by the interaction between superconducting vortices and the magnetic dipoles. Moreover, we find that these magnetic textures produce vortex-antivortex patterns, which have a crucial role in the transport properties of this hybrid system. [less ▲]

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See detailInfluence of magnet size on magnetically engineered field-induced superconductivity
Gillijns, W.; Milosevic, M. V.; Silhanek, Alejandro ULg et al

in Physical Review. B : Condensed Matter (2007), 76(18),

We investigate experimentally and theoretically the superconducting properties of an Al thin film covering a periodic array of Co/Pt magnetic disks with out-of-plane magnetization for different radii of ... [more ▼]

We investigate experimentally and theoretically the superconducting properties of an Al thin film covering a periodic array of Co/Pt magnetic disks with out-of-plane magnetization for different radii of the magnetic disks and constant period of the magnetic lattice. The presence of the arrays of magnetic dots leads to a quantized displacement of the normal/superconducting phase boundary along the magnetic field axis, with each step corresponding to a flux-quantum per unit cell of the magnetic lattice. We demonstrate that this so-called field-induced superconductivity is strongly dependent not only on the chosen magnetic material and its magnetization M but also on the radius R of the constructed magnetic disks. Since field-induced superconductivity is directly linked to the nucleation of vortex-antivortex (V-AV) pairs, a theoretical M-R equilibrium phase boundary is presented, delimiting regions of different numbers of induced V-AV pairs per magnet. A good qualitative and quantitative agreement is found between theory and experiment. [less ▲]

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See detailOrigin of reversed vortex ratchet motion
Gillijns, W.; Silhanek, Alejandro ULg; Moshchalkov, V. V. et al

in Physical Review Letters (2007), 99(24),

We experimentally demonstrate that the origin of multiply reversed rectified vortex motion in an asymmetric pinning landscape not only is a consequence of the vortex-vortex interactions but also ... [more ▼]

We experimentally demonstrate that the origin of multiply reversed rectified vortex motion in an asymmetric pinning landscape not only is a consequence of the vortex-vortex interactions but also essentially depends on the ratio between the characteristic interaction distance and the period of the asymmetric pinning potential. We study four samples with different periods d of the asymmetric potential. For large d the dc voltage V(dc) recorded under a ac excitation indicates that the average vortex drift is from bigger to smaller dots for all explored positive fields. As d is reduced, a series of sign reversals in the dc response are observed as a function of field. We show that the number of sign reversals increases as d decreases. These findings are in agreement with recent computer simulations and illustrate the relevance of the different characteristic lengths for the vortex rectification effects. [less ▲]

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See detailOptimization of superconducting critical parameters by tuning the size and magnetization of arrays of magnetic dots
Silhanek, Alejandro ULg; Gillijns, W.; Milosevic, M. V. et al

in Physical Review. B, Condensed Matter and Materials Physics (2007), 76(10),

We investigate the nucleation of superconductivity in an Al film deposited on top of an array of micromagnets with perpendicular anisotropy by dc transport measurements. The absolute control of the ... [more ▼]

We investigate the nucleation of superconductivity in an Al film deposited on top of an array of micromagnets with perpendicular anisotropy by dc transport measurements. The absolute control of the magnetic state of the ferromagnets enabled us to explore the superconductor-normal-metal phase boundary as a function of the magnetization M of the dots. For a given external homogeneous field H, the magnetization of the dots can be tuned in such a way to optimize the field and current compensation in the sample, thus yielding a clear enhancement of the upper critical field H-c2. In addition, we theoretically demonstrate that the critical current I-c for a given temperature could be further enhanced by properly adjusting the size of the magnetic dots. These results are fully corroborated by the Ginzburg-Landau theory as well as analytic estimates. [less ▲]

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See detailMagnetic confinement of the superconducting condensate in superconductor-ferromagnet hybrid composites
Gillijns, W.; Aladyshkin, A Yu; Silhanek, Alejandro ULg et al

in Physical Review. B : Condensed Matter (2007), 76(6),

The influence of an inhomogeneous magnetic field on the magnetoresistance of thin Al films, used in different superconductor-ferromagnet hybrids, has been investigated. Two contrasting magnetic textures ... [more ▼]

The influence of an inhomogeneous magnetic field on the magnetoresistance of thin Al films, used in different superconductor-ferromagnet hybrids, has been investigated. Two contrasting magnetic textures with out-of-plane magnetization are explored: namely, (i) a plain film in a multidomain state and (ii) an array of microsized dots. The stray fields of the ferromagnetic structures confine the superconducting condensate and, accordingly, modify the condition for the nucleation of superconductivity. By switching between different magnetic states of the ferromagnet, this confinement can be tuned at will, thereby reversibly changing the dependence of the critical temperature T-c on an external magnetic field H. In particular, continuous evolution from a conventional linear T-c(H) dependence with a single maximum to a reentrant superconducting phase boundary with multiple T-c peaks has been demonstrated. [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 detailReduction of Neel temperature of CeIn3 by la doping
Iwamoto, Y.; Ebihara, T.; Harrison, N. et al

in Journal of Magnetism & Magnetic Materials (2007), 310(2), 300-302

The Neel temperature of heavy fermion material CeIn3 is at 10 K. La doping to Ce site of CeIn3 introduces increase of distance between Ce ions and reduction of number of 4f electron. It is implied the ... [more ▼]

The Neel temperature of heavy fermion material CeIn3 is at 10 K. La doping to Ce site of CeIn3 introduces increase of distance between Ce ions and reduction of number of 4f electron. It is implied the reduction of 4f electron number with La doping weakens inter site magnetic interaction. An x-T phase diagram was drawn with Neel temperatures estimated from both electrical resistivity and magnetic susceptibility measurements. (c) 2006 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 detailSuperconducting microrings as magnetic pinning centers
Gillijns, W.; Silhanek, Alejandro ULg; Moshchalkov, V. V.

in Applied Physics Letters (2007), 91(20),

The nucleation of the superconducting condensate in an Al film deposited on top of a periodic array of microsized Pb rings is investigated using transport measurements. We demonstrate that these Pb rings ... [more ▼]

The nucleation of the superconducting condensate in an Al film deposited on top of a periodic array of microsized Pb rings is investigated using transport measurements. We demonstrate that these Pb rings form tunable pinning sites which can be switched at will to repel or attract vortices in the Al film, depending on their magnetic history. After zero field cooling, a repulsive interaction between the rings and the vortices is observed, while after field cooling, the interaction becomes attractive. The flexibility of such current-induced pinning centers can lead to an enhanced control over the vortex motion. (c) 2007 American Institute of Physics. [less ▲]

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See detailPhysical properties at high magnetic fields in CeIn2.75Sn0.25
Ebihara, T.; Harrison, N.; Jaime, M. et al

in Journal of Magnetism & Magnetic Materials (2007), 310(2), 298-299

High magnetic field induces quantum criticality in CeIn3 with suppressing the Neel temperature. Estimated quantum critical. efield of CeIn3 is about 60T where the Neel temperature is suppressed to reach ... [more ▼]

High magnetic field induces quantum criticality in CeIn3 with suppressing the Neel temperature. Estimated quantum critical. efield of CeIn3 is about 60T where the Neel temperature is suppressed to reach absolute zero. The magnetic. field (60T) is too high to measure electrical resistivity or specific heat precisely. Sn doping to In site of CeIn3 reduces the Neel temperature. Reduction of Neel temperature indicates lower critical. field to facilitate investigation of electronic states at high magnetic. fields. Electrical resistivity and specific. c heat in CeIn2.Sn-85(0.25) were measured to map an H-T phase diagram. (c) 2006 Elsevier B. V. All rights reserved. [less ▲]

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See detailManipulation of the vortex motion in nanostructured ferromagnetic/superconductor hybrids
Silhanek, Alejandro ULg; Gillijns, W.; Moshchalkov, V. V. et al

in Applied Physics Letters (2007), 90(18),

The authors investigate the rectified motion of vortices in superconducting films deposited on top of a close-packed array of open in-plane magnetized triangular micromagnets. The dc voltage induced by ... [more ▼]

The authors investigate the rectified motion of vortices in superconducting films deposited on top of a close-packed array of open in-plane magnetized triangular micromagnets. The dc voltage induced by the vortex drift under an ac excitation is recorded for three different magnetic configurations of the triangles. 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 triangles is magnetized the observed rectification effect is independent of the field polarity and can be reverted by reorienting the magnetization of the micromagnets. (C) 2007 American Institute of Physics. [less ▲]

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See detailIrreversible dynamics of the phase boundary in U(Ru(0.96)Rh(0.04))(2)Si(2) and implications for ordering
Silhanek, Alejandro ULg; Jaime, M.; Harrison, N. et al

in Physical Review Letters (2006), 96(13),

We report measurements and analysis of the specific heat and magnetocaloric effect-induced temperature changes at the phase boundary into the single magnetic field-induced phase (phase II) of U(Ru(0.96)Rh ... [more ▼]

We report measurements and analysis of the specific heat and magnetocaloric effect-induced temperature changes at the phase boundary into the single magnetic field-induced phase (phase II) of U(Ru(0.96)Rh(0.04))(2)Si(2), which yield irreversible properties similar to those at the valence transition of Yb(1-x)Y(x)InCu(4). To explain these similarities, we propose a bootstrap mechanism by which lattice parameter changes caused by an electric quadrupolar order parameter within phase II become coupled to the 5f-electron hybridization, giving rise to a valence change at the transition. [less ▲]

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See detailNonlocal magnetic field-tuned quantum criticality in cubic CeIn3-xSnx (x=0.25)
Silhanek, Alejandro ULg; Ebihara, Takao; Harrison, N. et al

in Physical Review Letters (2006), 96(20),

We show that antiferromagnetism in lightly (approximate to 8%) Sn-doped CeIn3 terminates at a critical field mu H-0(c)=42 +/- 2 T. Electrical transport and thermodynamic measurements reveal the effective ... [more ▼]

We show that antiferromagnetism in lightly (approximate to 8%) Sn-doped CeIn3 terminates at a critical field mu H-0(c)=42 +/- 2 T. Electrical transport and thermodynamic measurements reveal the effective mass m(*) not to diverge, suggesting that cubic CeIn3 is representative of a critical spin-density wave (SDW) scenario, unlike the local quantum critical points reported in anisotropic systems such as CeCu6-xAux and YbRh2Si2-xGex. The existence of a maximum in m(*) at a lower field mu H-0(x)=30 +/- 1 T may be interpreted as a field-induced crossover from local moment to SDW behavior as the Neel temperature falls below the Fermi temperature. [less ▲]

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See detailCrossover from intravalley to intervalley vortex motion in type-II superconductors with a periodic pinning array
Raedts, S.; Silhanek, Alejandro ULg; Moshchalkov, V. V. et al

in Physical Review. B : Condensed Matter (2006), 73(17),

We have determined the transition from intravalley vortex motion (Campbell regime) to intervalley motion (critical state regime) in Pb thin films with and without a square array of holes (antidots) by ... [more ▼]

We have determined the transition from intravalley vortex motion (Campbell regime) to intervalley motion (critical state regime) in Pb thin films with and without a square array of holes (antidots) by means of ac susceptibility chi(T,H) measurements. The Campbell regime is characterized by a maximum dissipation chi(')(max) 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 J(T) extracted from the chi(')(T) 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. [less ▲]

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See detailTunable field-induced superconductivity
Gillijns, W.; Silhanek, Alejandro ULg; Moshchalkov, V. V.

in Physical Review. B : Condensed Matter (2006), 74(22),

We investigate the transport properties of a thin superconducting Al layer covering a square array of magnetic dots with out-of-plane magnetization. A thorough characterization of the magnetic properties ... [more ▼]

We investigate the transport properties of a thin superconducting Al layer covering a square array of magnetic dots with out-of-plane magnetization. A thorough characterization of the magnetic properties of the dots allowed us to fine-tune their magnetic state at will, hereby changing the influence of the dots on the superconductor in a continuous way. We show that even though the number of vortex-antivortex pairs discretely increases with increasing the magnetization of the dots, no corresponding discontinuity is observed in the resistance of the sample. The evolution of the superconducting phase boundary as the magnetic state of the dots is swept permits one to devise a fully controllable and erasable field-induced superconductor. [less ▲]

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See detailLattice involvement in low temperature phase of U(Ru,Rh)(2)Si-2
Jaime, M.; Silhanek, Alejandro ULg; Kim, K. H. et al

in Physica B: Condensed Matter (2006), 378-80

Specific heat, magnetocaloric effect and magnetization experiments were performed on the 5f-electron system U(Ru0.96Rh0.04)(2)Si-2. This compound exhibits a non-magnetic ground state with a single ... [more ▼]

Specific heat, magnetocaloric effect and magnetization experiments were performed on the 5f-electron system U(Ru0.96Rh0.04)(2)Si-2. This compound exhibits a non-magnetic ground state with a single magnetic field-induced phase between H = 26 and 38 T. We show that the transition into this phase is first-order as revealed by a large irreversible specific heat anomaly and asymmetric magnetocaloric effect. A comparative analysis with the valence transition compound YbInCu4, where similar irreversibility and asymmetry exists, is presented. (c) 2006 Published by Elsevier B.V. [less ▲]

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See detailGamma(5) quasiparticles and avoided quantum criticality in U(Ru,Rh)(2)Si-2
Silhanek, Alejandro ULg; Harrison, N.; Batista, C. D. et al

in Physica B: Condensed Matter (2006), 378-80

We discuss recent specific heat data in high magnetic fields on URu2Si2 and 4% Rh-doped URu2Si2 as well as previously published de Haas-van Alphen data at lower magnetic fields in pure URu2Si2: both of ... [more ▼]

We discuss recent specific heat data in high magnetic fields on URu2Si2 and 4% Rh-doped URu2Si2 as well as previously published de Haas-van Alphen data at lower magnetic fields in pure URu2Si2: both of which are consistent with quasiparticle bands formed from a hybridization between 5f-electron Gamma(5) doublets and regular conduction electrons. The system exhibits itinerant electron metamagnetism that gives rise to a putative quantum critical point at similar to 34-37T (depending on the % of Rh) that is subsequently unstable to field-induced phases. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailApproaching field tuned quantum criticality in CeIn3-xSnx
Silhanek, Alejandro ULg; Zocco, D.; Harrison, N. et al

in Physica B: Condensed Matter (2006), 378-80

We report on the magnetic field evolution of the Neel temperature T-N in the heavy electron system CeIn3-xSnx (x = 0 and 0.3), as determined by specific heat, magnetocaloric effect, and electrical ... [more ▼]

We report on the magnetic field evolution of the Neel temperature T-N in the heavy electron system CeIn3-xSnx (x = 0 and 0.3), as determined by specific heat, magnetocaloric effect, and electrical transport measurements. For the stoichiometric compound, T-N is fully suppressed at H-c similar to 65 T, whereas for x = 0.3 the critical field extrapolates to H-c similar to 30 T. An increasing Sommerfeld coefficient gamma, obtained above T-N, as field increases is observed and could be related to the a putative quantum critical point at H-c. (c) 2006 Published by Elsevier B.V. [less ▲]

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