References of "Silhanek, Alejandro"
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See detailSimplifying strong electronic correlations in uranium: Localized uranium heavy-fermion UM(2)Zn(20) (M = Co, Rh) compounds
Bauer, E. D.; Wang, C.; Fanelli, V. R. et al

in Physical Review. B : Condensed Matter (2008), 78(11),

The physical properties including magnetic susceptibility, magnetization, specific heat, and dynamic susceptibility chi ''(E) are reported for single crystals of the cubic UM(2)Zn(20) (M = Co, Rh ... [more ▼]

The physical properties including magnetic susceptibility, magnetization, specific heat, and dynamic susceptibility chi ''(E) are reported for single crystals of the cubic UM(2)Zn(20) (M = Co, Rh) materials. Maxima in the thermodynamic data at T(max) similar to 10 K for both compounds and a broad peak in chi ''(E) at 5 K in UCo(2)Zn(20) of width Gamma=5 meV indicate a heavy-fermion state characterized by a Kondo temperature T(K) similar to 20-30 K arising from weak hybridization of f- and conduction-electron states. Anderson impurity model fits to the data in the Kondo limit including crystalline electric-field effects corroborate an ionic-like uranium electronic configuration in UM(2)Zn(20). [less ▲]

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See detailDifferent regimes of nucleation of superconductivity in mesoscopic superconductor/ferromagnet hybrids
Schildermans, N.; Aladyshkin, A Yu; Silhanek, Alejandro ULg et al

in Physical Review. B : Condensed Matter (2008), 77(21),

The competition between two regimes of the nucleation of superconductivity is investigated experimentally and theoretically in a mesoscopic disk-shaped superconductor/ferromagnet hybrid. By changing the ... [more ▼]

The competition between two regimes of the nucleation of superconductivity is investigated experimentally and theoretically in a mesoscopic disk-shaped superconductor/ferromagnet hybrid. By changing the magnetic state of a multilayered Co/Pt disk one can reversibly affect the magnetic-field dependence of the critical temperature T(c)(H) of an Al layer. We demonstrate that an enhancement of the magnetic field near the edge of the out-of-plane magnetized disk either stimulates the nucleation of superconductivity at the disk perimeter due to the field compensation effect or prevents it due to edge magnetic barrier (for relatively low parallel to H parallel to values). As a consequence, the presence of such magnetic-field pattern makes it possible to eliminate boundary effects for mesoscopic superconducting samples. Switching from one nucleation regime to another while sweeping H leads to an abrupt change of the slope of the T(c)(H) envelope. [less ▲]

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See detailMagnetic flux patterns in superconductors deposited on a lattice of magnetic dots: A magneto-optical imaging study
Gheorghe, Diana G; Wijngaarden, Rinke J; Gillijns, Werner et al

in Physical Review. B : Condensed Matter (2008), 77(5),

We investigate the flux penetration in Pb films, of different shapes, deposited on top of a periodic array of Co/Pt dots with perpendicular anisotropy by means of magnetization and magneto-optical ... [more ▼]

We investigate the flux penetration in Pb films, of different shapes, deposited on top of a periodic array of Co/Pt dots with perpendicular anisotropy by means of magnetization and magneto-optical measurements. A clear dependence of the critical current density on the magnetic state of the dots and their polarity with respect to the direction of the applied magnetic field is observed by both techniques. The magnetic state of the dots changes the flux penetration from smooth to channelling. Additionally, in the fully magnetized state, an anisotropic current distribution is observed in circular-shaped samples. The flux penetration is dominated by avalanches only for configurations which correspond to a high critical current, irrespective of its origin, be it low temperature, magnetization state of the dots, or angle between the lattice of dots and the edge of the sample. [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 detailSwitchable magnetic dipole induced guided vortex motion
Verellen, N.; Silhanek, Alejandro ULg; Gillijns, W. et al

in Applied Physics Letters (2008), 93(2),

We present evidence of magnetically controlled vortex motion in an Al film on top of a periodic array of Permalloy square rings. The resulting magnetic template generates a strongly anisotropic pinning ... [more ▼]

We present evidence of magnetically controlled vortex motion in an Al film on top of a periodic array of Permalloy square rings. The resulting magnetic template generates a strongly anisotropic pinning potential landscape for vortices in the superconducting layer. Transport measurements show that this anisotropy is able to confine the flux motion along the high symmetry axes of the square lattice of dipoles. This guided vortex motion can be rerouted by 90 degrees simply changing the dipole orientation or even suppressed by inducing a flux-closure magnetic state with very low stray fields in the rings. (C) 2008 American Institute of Physics. [less ▲]

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See detailComment on "Transverse rectification in superconducting thin films with arrays of asymmetric defects" [Appl. Phys. Lett. 91, 062505 (2007)]
Silhanek, Alejandro ULg; de Vondel, J Van; Moshchalkov, V. V. et al

in Applied Physics Letters (2008), 92(17),

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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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