Low temperature X-ray imaging of magnetic flux patterns in high temperature superconductors

• Published in: Journal of applied physics 2015-05, Vol.117 (17)
• Main Authors: Stahl, Claudia, Ruoß, Stephen, Weigand, Markus, Bechtel, Michael, Schütz, Gisela, Albrecht, Joachim
• Format: Article
• Language: English
• Subjects: Current distribution; Dichroism; High temperature superconductors; Liquid nitrogen; Low temperature; Magnetic flux; Magnetism; Microscopy; Thin films; X ray microscopy; YBCO superconductors
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4907764

We present X-ray magnetic circular dichroism (XMCD) microscopy results obtained at liquid nitrogen temperatures on the high-Tc superconductor YBCO (YBa2Cu3O7–δ). The magnetic flux distribution arising from electric currents in the superconductor is detected and visualized using soft-magnetic Co40Fe40B20 (CoFeB) as sensor layer and XMCD as contrast mechanism. It has been shown that the XMCD contrast in the sensor layer directly corresponds to magnetic flux distribution of the superconductor and hence can be used to image magnetic structures in superconductors [Stahl et al., Phys. Rev. B 90, 104515 (2014)]. The existing scanning UHV X-ray microscopy setup MAXYMUS at the synchrotron BESSY II in Berlin has been upgraded for that purpose: we use a nitrogen based MMR Micro Miniature Joule-Thompson Cryostat with temperature range from 75 K to 580 K. The capability of the method is demonstrated on two different superconducting samples, an optimally doped thin film and a melt-textured block.