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Vortex matter beyond SANS

Mardi 7 février 2017 11:00 - Duree : 1 heure
Lieu : ILL 4, Seminar Room (no 163), 71 avenue des Martyrs - Grenoble

Orateur : Tommy REIMANN (FRM2 - Munich - Germany)

Magnetic vortices in type-II superconductors are exposed to a variety of different interactions like inter-vortex repulsion (or attraction), pinning forces, thermal activation or correlations to the crystal lattice. The interplay of these interactions gives rise to surprisingly complex phase diagrams within the vortex state including e.g. crystalline, liquid, and glassy configuration. The crystallography of this “vortex matter” and transitions within are routinely probed by means of small-angle neutron scattering (SANS), since it covers the length scale of the typical inter-vortex distance of approx. 100 nm [1].

When investigating vortex matter, the influence of the sample shape is however rarely considered, even though it can induce a strongly inhomogeneous distribution of vortices and under some circumstances even provoke the nucleation of a vortex lattice domain structure. Due to the lack of real as well as reciprocal space resolution on the appropriate length scale, both effects cannot be sufficiently studied by means of SANS.

The presentation will discuss how the combination of the advanced neutron imaging method neutron grating interferometry (nGI) [2] with ultra-small-angle neutron scattering (USANS) reveals the impact of the sample geometry onto the vortex phase in the elementary type-II\1 superconductor Niobium. While USANS is capable to probe the morphology of the µm vortex domains which nucleate as a consequence of the sample shape, nGI allows to directly map their spatial distribution within the sample [3].

The presented approach is by no means restricted to vortex matter. It can be extended in order to investigate the variety of modulated phases appearing in various other physical, chemical or biological systems, systems near phase transitions, as well as in emerging magnetic systems.

[1] M. R. Eskildsen, E. M. Forgan, H Kawano-Furukawa, Rep. Prog. Phys. 74, 124504 (2011)

[2] T. Reimann et al., J. Appl. Cryst. 49, 1488 (2016)

[3] T. Reimann et al., Nat. Commun. 6:8813 (2015)

Contact : dubouloz@ill.fr

Discipline évènement : (Physique)
Entité organisatrice : (ILL)
Nature évènement : (Séminaire)
Evènement répétitif : (General ILL Seminar - College 1)
Site de l'évènement : Polygone scientifique

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