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TT: Fachverband Tiefe Temperaturen

TT 30: Superconductivity - Poster Session

TT 30.3: Poster

Montag, 31. März 2014, 15:00–19:00, P2

Direct measurement of the magnetic anisotropy of thin sputtered MgB₂ films on MgO substrates in high magnetic fields — •Savio Fabretti¹, Inga-Mareen Imort¹, Timo Kuschel¹, Thomas Dahm¹, Andy Thomas^1,2, Veerendra K. Guduru³, and Uli Zeitler³ — ¹Bielefeld University, Bielefeld, Germany — ²Johannes Gutenberg, Mainz, Germany — ³Radboud University, Nijmegen, Netherlands

We investigated the magnetic anisotropy ratio of thin sputtered polycrystalline MgB₂ films on MgO substrates. Using high magnetic field measurements, we estimated an anisotropy ratio of 1.35 for T=0 K with an upper critical field of 31.74 T in the parallel case and 23.5 T in the perpendicular case. Direct measurements of a magnetic-field sweep at 4.2 K show a linear behavior, confirmed by a linear fit for magnetic fields perpendicular to the film plane. At an applied magnetic field parallel to the film plane, a deviation from the upper critical field of 3 T was observed by using magnetic sweep measurements; this deviation may be attributable to the different crystal sizes in the polycrystalline films. Furthermore, we observed a change of up to 12% of the anisotropy ratio in dependence of the film thickness.