Magnetic flux penetration into micron-sized superconductor/ferromagnet bilayers. (14th January 2020)

• Record Type: Journal Article
• Authors: Simmendinger, J; Weigand, M; Schütz, G; Albrecht, J
• Is Part Of: Superconductor science & technology. Volume 33:Number 2(2020:Feb.)
• Publication Date: 2020-01-14
• Subjects: flux penetration -- superconducting thin films -- magnetic x-ray microscopy -- superconductor/ferromagnet structures; Superconductivity -- Periodicals; Superconductors -- Periodicals; 537.623
• DOI: 10.1088/1361-6668/ab54ab
• Languages: English
• ISSNs: 0953-2048

Abstract

Abstract: Flux penetration into small superconductor/ferromagnet elements is investigated by magneto-optical imaging and magnetic scanning transmission x-ray microscopy at low temperatures. It is found that penetration of magnetic flux into a thin bilayer of YBCO and Py strongly depends on the direction of a perpendicular magnetic field. The soft-magnetic layer acts as an amplifier for magnetic in-plane components that are generated by electric currents in the superconductor. These in-plane components point in opposite direction above the ferromagnet and below the superconductor. As a consequence a strong inclination of the local magnetic field occurs that significantly slows down or speeds up the flux penetration into such elements. From detailed magnetic scanning x-ray microscopy results it is found that the effect dramatically increases if the elements get smaller. In 20 × 20 μ m 2 superconducting squares we observe magnetic flux penetration that differs by more than a factor of four when reversing the external magnetic field.