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17–19 Sept 2018
Fakultät für Maschinenwesen der Technischen Universität München
Europe/Berlin timezone

Vortex Lattice Domain Formation in the Type-II/1 Superconductor Niobium

18 Sept 2018, 11:00
15m
MW 0001 (Fakultät für Maschinenwesen)

MW 0001

Fakultät für Maschinenwesen

Talk P4 Magnetism and quantum phenomena Parallel session 4

Speaker

Alexander Backs (Heinz Maier-Leibnitz Zentrum, Technische Universität München)

Description

Besides the well-known vortex lattice (VL), type-II/1 superconductors exhibit the intermediate mixed state (IMS), where VL domains and Meissner domains coexist, due to an attractive component of the VL interaction [1]. Despite some work in the 1970s, no detailed theoretical model for the IMS exists. Primary obstacles are the inapplicability of most standard models of superconductivity and the importance of demagnetization effects and vortex pinning.

We have readdressed the IMS in bulk niobium by combining several neutron based techniques [2],[3]. Using small angle scattering, we characterized the VL crystallography. For the larger IMS domains, we used ultra-small angle scattering to investigate the domain morphology. Additionally, neutron grating interferometry revealed information about the spatial distribution of IMS domains.

Following a field cooling protocol, we find that while the macroscopic magnetic properties remain homogeneous, vortices are gradually rearranged microscopically from a uniform VL to inhomogeneous domains. Surprisingly, this process takes place below the macroscopic freezing transition of the VL. The IMS domains form at a preferred length scale which remains nearly unchanged with temperature. These results shed new light on the detailed formation of the IMS in bulk superconductors.
[1] E. H. Brandt and M. P. Das, J. Supercond. Novel Magn. 24, 57 (2011)
[2] T. Reimann, et al, Nat. Com. 6, 8813 (2015)
[3] T. Reimann, et al, Phys. Rev. B 96(14), 144506 (2017)

Primary authors

Alexander Backs (Heinz Maier-Leibnitz Zentrum, Technische Universität München) Tommy Reimann (Heinz Maier-Leibnitz Zentrum, Technische Universität München) Michael Schulz (Heinz Maier-Leibnitz Zentrum, Technische Universität München) Mr Vitaliy Pipich (Jülich Centre for Neutron Science, Heinz Maier-Leibnitz Zentrum) Sebastian Muehlbauer (Heinz Maier-Leibnitz Zentrum) Prof. Peter Böni (Technische Universität München)

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