Dresden 2003 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 1: Mesoskopische Systeme I

TT 1.1: Hauptvortrag

Montag, 24. März 2003, 09:30–10:00, HSZ03

Field-induced superconductivity in films with magnetic dots — •Martin Lange, Margriet J. Van Bael, and Victor V. Moshchalkov — Laboratorium voor Vaste-Stoffysica en Magnetisme, K. U. Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium

Magnetic-field-induced superconductivity (FIS) is a rare phenomenon that has been observed up to now in only very few materials. We show that this effect can be generated in thin type-II superconducting Pb films by covering them with nanoengineered arrays of Co/Pd dots with perpendicular magnetic anisotropy. The observed effect is not limited by the chosen materials (Pb and Co/Pd) but is a general property of any type-II film with an array of dots with perpendicular anisotropy. For small magnetic dots, the magnetization curve of the superconductor is extremely asymmetric with respect to the polarity of the applied field. FIS is observed in transport measurements when the stray field of the dots is strong enough to induce stable vortex-antivortex pairs in the superconductor: A magnetic field applied perpendicular to the sample surface compensates the returning stray field between the dots, resulting in the appearance of FIS. This effect can be controlled by varying the distance between the dots or the amount of magnetic material in each dot.

This work was supported by the F.W.O. - Flanders, and by the Belgian IUAP, the Flemish GOA and the European ESF No-dqVORTEXNo-dq Programs.