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ABSTRACT: In this communication we present our response to the recent comment of Engel regarding our paper on FIB-fabricated Nb nanowires (see Tettamanzi et al 2009 20 465302). After further analysis and additional experimental evidence, we conclude that our interpretation of the experimental results in light of QPS theory is still valid when compared with the alternative proximity-based model as proposed by Engel.
Nanotechnology 04/2010; 21(16):168002. · 3.98 Impact Factor
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ABSTRACT: In this communication we present our response to the recent comment of A. Engel regarding our paper on FIB- fabricated Nb nanowires (see Vol. 20 (2009) Pag. 465302). After further analysis and additional experimental evidence, we conclude that our interpretation of the experimental results in light of QPS theory is still valid when compared with the alternative proximity-based model as proposed by A. Engel. Comment: 3 pages, 1 figure, accepted by Nanotechnology
03/2010;
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ABSTRACT: Making use of focused Ga-ion beam (FIB) fabrication technology, the evolution with device dimension of the low-temperature electrical properties of Nb nanowires has been examined in a regime where crossover from Josephson-like to insulating behaviour is evident. Resistance-temperature data for devices with a physical width of order 100 nm demonstrate suppression of superconductivity, leading to dissipative behaviour that is shown to be consistent with the activation of phase-slip below T(c). This study suggests that by exploiting the Ga-impurity poisoning introduced by the FIB into the periphery of the nanowire, a central superconducting phase-slip nanowire with sub-10 nm dimensions may be engineered within the core of the nanowire.
Nanotechnology 11/2009; 20(46):465302. · 3.98 Impact Factor
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ABSTRACT: We have studied the superconducting properties of sputtered multilayers of Nb / Pd / Fe . This structure is expected to exhibit a double proximity effect as both superconducting and ferromagnetic orders propagate into the Pd layer from the interfaces with Nb and Fe, respectively. By measuring samples with varying Pd thickness, we estimated that double proximity is present in the Pd layers with thickness up to 40 Å . Measurements of structural, superconducting, and magnetic behaviors, in samples with varying Fe thickness showed that the Pd spacer removes the alloying between Nb and Fe opening the way for the occurrence of reentrant superconducting effects in this system.
Journal of Applied Physics 05/2008; · 2.17 Impact Factor
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ABSTRACT: Hall probe microscopy has been used to image vortex-antivortex molecules induced in superconducting Pb films by the stray fields from square arrays of magnetic dots. We have directly observed spontaneous vortex-antivortex pairs and studied how they interact with added free (anti)fluxons in an applied magnetic field. We observe a variety of phenomena arising from competing symmetries which either drive added antivortices to join antivortex shells around dots or stabilize the translationally symmetric antivortex lattice between the dots. Added vortices annihilate antivortex shells, leading first to a stable "nulling state" with no free fluxons and then, at high densities, to vortex shells around the dots stabilized by the asymmetric antipinning potential. Our experimental findings are in good agreement with Ginzburg-Landau calculations.
Physical Review Letters 10/2007; 99(12):127001. · 7.37 Impact Factor
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ABSTRACT: We have investigated CuNi/Nb/CuNi trilayers, as have been recently used as the core structure of a spin-valve like device [J. Y. Gu et al., Phys. Rev. Lett. 89, 267001 (2002)] to study the effect of magnetic configurations of the CuNi layers on the critical temperature, Tc, of the superconducting Nb. After reproducing a Tc shift of a few mK, we have gone on to explore the performance limits of the structure. The results showed the Tc shift we found to be quite close to the basic limits of this particular materials system. The ratio between the thickness and the coherence length of the superconductor and the interfacial transparency were the main features limiting the Tc shift.
06/2005;
