151 research outputs found
Superconducting Supercomputers and Quantum Computation
Information technologies have been developing at a formidable pace. While miniaturization has been the driver for this in the past decades (Moore\u27s law), the attention is now focusing to the energy consumption. Already a considerable fraction of the worlds\u27 energy use is in information technologies. Also, the on-chip energy dissipation and concomittant high temperatures form a bottleneck in further speeding up processors. For these reasons a great interest exist in the exploration of new computing paradigms. In my presentation, I will introduce two of such paradigms and discuss their current progress and prospects, namely superconducting \u27RSQF\u27 circuitry and quantum-computation. Both technologies require (ultra)-low temperatures, providing interesting challenges for cryogenic engineering
Analysis of low-field isotropic vortex glass containing vortex groups in YBa2Cu3O7−x thin films visualized by scanning SQUID microscopy
The glass-like vortex distribution in pulsed laser deposited YBa2Cu3O7 − x thin films is observed by scanning superconducting quantum interference device microscopy and analysed for ordering after cooling in magnetic fields significantly smaller than the Earth\u27s field. Autocorrelation calculations on this distribution show a weak short-range positional order, while Delaunay triangulation shows a near-complete lack of orientational order. The distribution of these vortices is finally characterised as an isotropic vortex glass. Abnormally closely spaced groups of vortices, which are statistically unlikely to occur, are observed above a threshold magnetic field. The origin of these groups is discussed, but will require further investigation
Structure and magnetic properties of epitaxial CaFe2O4 thin films
CaFe2O4 is a highly anisotropic antiferromagnet reported to display two spin
arrangements with up-up-down-down (phase A) and up-down-up-down (phase B)
configurations. The relative stability of these phases is ruled by the
competing ferromagnetic and antiferromagnetic interactions between Fe3+ spins
arranged in two different environments, but a complete understanding of the
magnetic structure of this material does not exist yet. In this study we
investigate epitaxial CaFe2O4 thin films grown on TiO2 (110) substrates by
means of Pulsed Laser Deposition (PLD). Structural characterization reveals the
coexistence of two out-of-plane crystal orientations and the formation of three
in-plane oriented domains. The magnetic properties of the films, investigated
macroscopically as well as locally, including highly sensitive Mossbauer
spectroscopy, reveal the presence of just one order parameter showing
long-range ordering below T = 185 K and the critical nature of the transition.
In addition, a non-zero in-plane magnetization is found, consistent with the
presence of uncompensated spins at phase or domain boundaries, as proposed for
bulk samples.Comment: Changes are made to take into account the newly published paper by
Songvilay et al. (PRB 101,014407) Changes are in last sentence of the
abstract, 5th paragraph of the discussion section and conclusions paragrap
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