Author
Xavier Chaud
Other affiliations: Joseph Fourier University, Intelligence and National Security Alliance, University of Grenoble
Bio: Xavier Chaud is an academic researcher from Centre national de la recherche scientifique. The author has contributed to research in topics: Superconductivity & Magnet. The author has an hindex of 25, co-authored 161 publications receiving 2339 citations. Previous affiliations of Xavier Chaud include Joseph Fourier University & Intelligence and National Security Alliance.
Papers published on a yearly basis
Papers
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TL;DR: Using polarized elastic neutron diffraction, the authors identified a novel magnetic order in the YB(2)Cu(3)O(6+) system, which preserves translational symmetry of the lattice.
Abstract: One of the leading issues in high-T(c) superconductors is the origin of the pseudogap phase in underdoped cuprates. Using polarized elastic neutron diffraction, we identify a novel magnetic order in the YB(2)Cu(3)O(6+) system. The observed magnetic order preserves translational symmetry of the lattice as proposed for orbital moments in the circulating current theory of the pseudogap state. To date, it is the first direct evidence of a hidden order parameter characterizing the pseudogap phase in high-T(c) cuprates.
411 citations
TL;DR: In this article, a Ni45Co5Mn37.5In12.5 single crystal at room temperature was shown to have a capacity of 267 J/Kg at 7 T, which is very encouraging for magnetic refrigeration applications.
Abstract: A large inverse magnetocaloric effect has been observed in a Ni45Co5Mn37.5In12.5 single crystal at room temperature. Magnetothermal measurements performed at different magnetic fields reveal a nonmagnetic to ferromagnetic transition correlated with the austenite-martensite phase transformation. The Heusler single crystal shows a large entropy change of 30 J/Kg K at an applied magnetic field of 7 T during the first-order magnetostructural transition at 355 K. It leads to a net refrigerant capacity of 267 J/Kg at 7 T, which is very encouraging for magnetic refrigeration applications.
95 citations
TL;DR: In this paper, a solution-coating of NiO and CoO onto the surface of the carbon nanofibers was proposed to align them in the polymer composites under a moderate magnetic field.
Abstract: Engineering applications of carbon nanofibers and nanotubes require their alignment in specific directions. Single-walled carbon nanotubes can be aligned in a magnetic field due to the presence of small amounts of catalyst elements, such as Ni and Co. However, for carbon nanofibers, their extremely low magnetic susceptibility is not sufficient for magnetically induced alignment. We present a method of solution-coating of NiO and CoO onto the surface of the carbon nanofibers. Due to the NiO- and CoO-coating, these nanofibers can be well aligned in the polymer composites under moderate magnetic field (3 T). Both transmission electron microscopy and scanning electron microscopy results show the well-aligned nanofibers in a polymer matrix. Mechanical testing shows a pronounced anisotropy in tensile strength in directions normal (12.1 MPa) and parallel (22 MPa) to the applied field, resulting from the well-aligned nanofibers in the polymer matrix. The mechanism of magnetic alignment due to coating of NiO and CoO on the nanofiber surface is discussed.
72 citations
TL;DR: In this paper, the authors used bulk-textured YBa2Cu3O7-x single domains for current-limiting applications by cutting and assembling long meanders, which would be submitted to network electric fields before using a breaker to interrupt a fault current.
Abstract: Bulk-textured YBa2Cu3O7-x single domains could be used for current-limiting applications by cutting and assembling long meanders, which would be submitted to network electric fields before using a breaker to interrupt a fault current. For that purpose, large YBaCuO single domains up to 93 mm in diameter can be isothermally grown by using a standard melt texturing growth (MTG) process with a SmBaCuO seed. The essential parameters that have to be controlled in order to reach this size are the temperature growth window, the substrate reactivity and the temperature homogeneity in the sample. Standard 45 mm diameter single domains show excellent superconducting properties, such as Jc above 105 A cm-2 and a homogeneous superconducting-to-normal transition at 91.8 K for 20 cm long conductors cut in these pellets. These measurements demonstrate the long -range homogeneity of single domains regarding Tc and Jc. Nevertheless the high Jc values lead to a too large a dissipation in the normal state at T = 77 K. Different methods to reduce the critical current density are described in order to fulfill the conditions for a safe recovery of the material after undergoing a magnetothermal transition.
55 citations
TL;DR: In this paper, commercial MgB2 powders were sintered with an applied mechanical pressure, leading to Mg-B2 pellets with 99% relative density, and the critical current density was measured equal to 5.6 × 104 A/cm2 at 20
Abstract: Spark Plasma Sintering is a promising rapid consolidation technique that allows a better understanding and manipulating of sintering kinetics and therefore makes it possible to obtain MgB2-based ceramics with tailored microstructures. Commercial MgB2 powders were spark plasma sintered with an applied mechanical pressure, leading to MgB2 pellets with 99% relative density. The obtained samples show a sharp superconducting transition with an onset at 38.5 K. The critical current density was measured equal to 5.6 × 104 A/cm2 at 20 K under 1 T applied field. Otherwise, the trapped field was also investigated. A 5 mm thick pellet with a 20 mm diameter prepared with optimized processing temperature demonstrated a trapped field of 1.2 T at 15 K and up to 2.5 T at 10 K.
51 citations
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TL;DR: The discovery of high-temperature superconductivity in the copper oxides in 1986 triggered a huge amount of innovative scientific inquiry but unresolved issues include the astonishing complexity of the phase diagram, the unprecedented prominence of various forms of collective fluctuations, and the simplicity and insensitivity to material details of the ‘normal’ state at elevated temperatures.
Abstract: The discovery of high-temperature superconductivity in the copper oxides in 1986 triggered a huge amount of innovative scientific inquiry. In the almost three decades since, much has been learned about the novel forms of quantum matter that are exhibited in these strongly correlated electron systems. A qualitative understanding of the nature of the superconducting state itself has been achieved. However, unresolved issues include the astonishing complexity of the phase diagram, the unprecedented prominence of various forms of collective fluctuations, and the simplicity and insensitivity to material details of the 'normal' state at elevated temperatures.
1,859 citations
TL;DR: A phenomenological model is established that reveals the parameters essential for such a large adiabatic temperature change ΔT(ad), and it is demonstrated that obstacles to the application of Heusler alloys can be overcome by using the multi-response to different external stimuli and/or fine-tuning the lattice parameters.
Abstract: Magnetic cooling could be a radically different energy solution that could replace conventional vapour compression refrigeration in the future. It is now shown that a Heusler-type magnetocaloric alloy exhibits a remarkable cooling capability due to the effect of a sharp structural transformation at a specific temperature. The finding may be of relevance beyond Heusler alloys and represents an important step towards the implementation of cooling systems based on magnetocaloric materials.
1,233 citations
TL;DR: The magnetocaloric effect and its most straightforward application, magnetic refrigeration, are topics of current interest due to the potential improvement of energy efficiency of cooling and temperature control systems, in combination with other environmental benefits associated to a technology that does not rely on the compression/expansion of harmful gases.
941 citations
TL;DR: The concept that superconductivity competes with other orders in cuprate superconductors has become increasingly apparent, but obtaining direct evidence with bulk-sensitive probes is challenging as discussed by the authors.
Abstract: The concept that superconductivity competes with other orders in cuprate superconductors has become increasingly apparent, but obtaining direct evidence with bulk-sensitive probes is challenging We have used resonant soft x-ray scattering to identify two-dimensional charge fluctuations with an incommensurate periodicity of ~32 lattice units in the copper-oxide planes of the superconductors (Y,Nd)Ba(2)Cu(3)O(6+)(x), with hole concentrations of 009 to 013 per planar Cu ion The intensity and correlation length of the fluctuation signal increase strongly upon cooling down to the superconducting transition temperature (T(c)); further cooling below T(c) abruptly reverses the divergence of the charge correlations In combination with earlier observations of a large gap in the spin excitation spectrum, these data indicate an incipient charge density wave instability that competes with superconductivity
899 citations