Dresden 2014 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 81: Superconductivity: Properties and Electronic Structure
TT 81.9: Vortrag
Donnerstag, 3. April 2014, 11:45–12:00, HSZ 201
Magnetic characterization of bulk MgB2 — Alex Wiederhold1, •Michael R. Koblischka1, Miryala Muralidhar2, Masato Murakami2, Thomas Hauet3, and Uwe Hartmann1 — 1Institute of Experimental Physics, Saarland University, Campus C 6 3, D-66123 Saarbrücken, Germany — 2Department of Materials Science and Engineering, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548, Japan — 3Institute Jean Lamour, University of Lorraine, Vandœuvre-les-Nancy, France
A series of disk-shaped, bulk MgB2 superconductors (sample diameter up to 4 cm) was prepared in order to improve the performance for superconducting super-magnets. Several samples were fabricated using a solid state reaction in pure Ar atmosphere from 750 to 950 ∘C to obtain the highest critical current density as well as large trapped field values. Microstructural observations obtained from scanning electron microscopy (SEM) and atomic force microscopy (AFM) indicated that the grain size is the crucial parameter to improve the critical currents as well as the trapped field values. The small samples cut from the large bulks were characterized by transport measurements (R(T,B) and I/V characteristics) in magnetic fields up to 8 T and by magnetization loops measured by SQUID magnetometry. The pinning force analysis revealed a well developed scaling of the pinning force Fp = jc × B data with p= 0.65, q= 1.35 and a peak at h0= 0.32, indicating pinning at normal conducting precipitates. Similar values are obtained in the literature for pure, small MgB2 samples.