In the intermediate mixed state (IMS) of type-II/1 superconductors, vortex lattice (VL) and Meissner state domains coexist due to a partially attractive vortex interaction. Using a neutronbased multiscale approach combined with magnetization measurements, we study the continuous decomposition of a homogeneous VL into increasingly dense domains in the IMS in bulk niobium samples of varying purity. We find a universal temperature dependence of the vortex spacing, closely related to the London penetration depth and independent of the external magnetic field. The rearrangement of vortices occurs even in the presence of a flux freezing transition, i.e. pronounced pinning, indicating a breakdown of pinning at the onset of the vortex attraction.Conventional superconductors are divided by the Ginzburg-Landau parameter κ into type-I (κ < 1/ √ 2) and type-II (κ > 1/ √ 2), which, additionally to the Meissner state (MS) exhibit the Shubnikov state (SS). In the SS, magnetic vortices form a variety of vortex matter (VM), such as the Abrikosov vortex lattice (VL) [1], glassy [2][3][4] or liquid [5][6][7] states. Type-II superconductors are further subdivided, where type-II/2 (κ 1/ √ 2) features a purely repulsive inter-vortex interaction. In type-II/1(κ ≈ 1/ √ 2) the interaction acquires an attractive component [8][9][10], which favors the formation of vortex clusters, leaving behind MS regions. The resulting domain structure is denoted the intermediate mixed state (IMS).The IMS in the type-II/1 superconductor niobium (Nb) is an ongoing research topic since its first observation via Bitter decoration in 1967 [11,12]. Despite numerous experimental [9, 13-16] and theoretical [8, 10, 17, 18] efforts, its properties are not yet fully understood. The interplay of repulsive and attractive vortex interactions and the consequences on the domain structure in superconducting VM have found renewed interest with the discovery of multiband superconductors, especially MgB 2 (sometimes denoted as type-1.5) [19]. Apart from superconducting properties, the IMS is also a model system for universal domain physics [20], as it can be tuned readily by temperature and magnetic field [21].Previous studies primarily investigated the zero field cooled (ZFC) field dependence of the IMS. However, this approach leads to strong magnetic inhomogeneities due to geometric and demagnetization effects reflected in the critical state model [22,23]. In contrast, our systematic study focuses on the temperature dependence during a field cooling (FC) and subsequent field heating (FC/FH) protocol in bulk Nb samples with distinct pinning properties. The phase diagram and the transition from a ho- * alexander.Backs@frm2.tum.de † sebastian.muehlbauer@frm2.tum.de mogeneous VL in the SS to the increasingly dense VL domains in the IMS is sketched in Fig. 1 on a FC path. FIG. 1.Schematic phase diagram of a type-II/1 superconductor, subdivided into MS, IMS and SS. Arrows depict different measurement protocols: FC, FC/FH and ZFC/FH. For FC measurements, the microscopic magnet...

neutron grating interferometry (nGi) is a unique technique allowing to probe magnetic and nuclear properties of materials not accessible in standard neutron imaging. the signal-to-noise ratio of an nGI setup is strongly dependent on the achievable visibility. Hence, for analysis of weak signals or short measurement times a high visibility is desired. We developed a new talbot-Lau interferometer using the third Talbot order with an unprecedented visibility (0.74) over a large field of view. Using the third talbot order and the resulting decreased asymmetry allows to access a wide correlation length range. Moreover, we have used a novel technique for the production of the absorption gratings which provides nearly binary gratings even for thermal neutrons. the performance of the new interferometer is demonstrated by visualizing the local magnetic domain wall density in electrical steel sheets when influenced by residual stress induced by embossing. We demonstrate that it is possible to affect the density of the magnetic domain walls by embossing and therefore to engineer the guiding of magnetic fields in electrical steel sheets. The excellent performance of our new setup will also facilitate future studies of dynamic effects in electric steels and other systems. Neutron radiography is a method allowing for non-destructive analysis of the inner structure of an object 1. Because the neutron cross-sections show no systematic dependence on the atomic number, both light and heavy elements can be visualized. Moreover, the contrast between different materials can be varied by using isotopes. Therefore, neutron imaging has been established to be a very efficient technique in materials science, research in cultural heritage, archaeology, and engineering, where imaging with X-rays fails to produce sufficient contrast. Neutron imaging is, however, limited by the coarse spatial resolution imposed by the limitations in neutron flux and the spatial resolution of the neutron detectors. Currently, the achieved spatial resolution is in the low single μm range 2-7. Paths towards resolving structures with higher resolution (e.g. water transport in fuel cells) are, for example, improving the detector resolution 3-6 or in some cases using neutron grating interferometry (nGI) 8,9 as a spatially resolved ultra-small-angle scattering technique. nGI simultaneously gathers spatially resolved information about the transmission-(TI), the differential phase contrast-(DPCI) and the scattering/dark-field (DFI) of a sample. Most notably, the contrast provided by the DFI 10,11 is generated by ultra-small-angle neutron scattering (USANS) off structures on a length scale similar to the correlation length of the interferometer setup, which is typically in the range 0.1 μm to 10 μm. Such structures are caused by variations of the nuclear or magnetic

The imaging performance of a neutron-based Talbot-Lau interferometer depends to a great extent on the absorption characteristics of the source and analyzer gratings. Due to its high neutron attenuation, gadolinium (Gd) is the preferred material for grating fabrication, but suffers from difficulties with deposition time, stability, uniformity, and selectivity into high aspect ratio structures. Here we present a simple alternative method of Gd deposition into grating structures based on metallic particle suspension casting and subsequent doctor-blading. Surface analysis by confocal and electron scanning microscopy shows that a nearly clear, particle free silicon interface of the grating structure over a large area could be reached. Additionally, characterization by neutron radiography confirms a high effective Gd height and homogeneity over the whole grating area. In particular, grating trenches well below 10 μm width could be successfully filled with Gd and deliver excellent absorbing performance down to the sub-2 Å wavelength range. The findings confirm that we obtained an effective binary absorption profile for the fabricated gratings which is of great benefit for grating-based neutron imaging.