Thermodynamics of Meissner effect and flux pinning behavior in the bulk of single crystal La2 xSrxCuO4 x 0.09

We have studied the evolution of magnetic flux pinning behavior in the Meissner phase and the mixed state for the high- T c single-crystal La 2 − x Sr x CuO 4 ( x = 0.09 ) superconductor using the polarized neutron imaging method with varying magnetic field and temperature. In the Meissner state expulsion of magnetic field (switched on during the measurements) is visualized, and the signatures of a mixed state with increasing temperature are observed. However, for flux pinning behavior in the range 5 K ≤ T ≤ 15 K and H ext = 63.5 mT (switched off during the measurements), the evolution of the fringe pattern indicates magnetic flux pinning inside the bulk of the sample. At 25 K ≤ T ≤ 32 K , a continuous decrease in inhomogeneously distributed pinned magnetic flux is observed, with the sample reaching a normal conducting state at T c ( ≈ 32 K). The flux pinning behavior is also explored as a function of H ext at T = 5 K . As expected, with increasing H ext an increase in fringe density is observed, indicating an increase in magnetic flux pinning in the bulk of the sample. A comparison between calculated and experimentally visualized pinned magnetic fluxes shows good agreement. This implies quantification of pinned magnetic flux inside the sample, which is not possible with any other technique for bulk samples

X ray and neutron imaging Complementary techniques for materials science and engineering

International audienceUsing X-ray and neutron radiography and tomography, images of material and component inhomogeneities and their development with time can be obtained. Due to their non-destructiveness and non-invasive nature both methods give insight into the function of devices and their decay processes. Fundamentals of X-ray and neutron radiography and tomography are briefly outlined, examples for both techniques are given, their complementarities are highlighted and emerging techniques and frontiers are discussed