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TT: Fachverband Tiefe Temperaturen

TT 46: SC: Tunneling, Josephson Junctions, SQUIDs 1

TT 46.6: Vortrag

Donnerstag, 17. März 2011, 12:00–12:15, HSZ 301

Sensitive dc SQUIDs for detection of small spin systems — •R. Wölbing¹, J. Nagel¹, M. Kemmler¹, K. Konovalenko¹, M. Turad¹, R. Werner¹, R. Kleiner¹, D. Koelle¹, O. Kieler², T Weimann², J. Kohlmann², A. Zorin², E. Kleisz³, S. Menzel³, B. Büchner³, and R. Klingeler³ — ¹Physikalisches Institut - Experimentalphysik II and Center for Collective Quantum Phenomena, Universität Tübingen, 72076 Tübingen, Germany — ²Fachbereich 2.4 "Quantenelektronik", Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany — ³Leibnitz-Institut für Festkörper- und Werkstoffforschung (IFW) Dresden, 01171 Dresden, Germany

Investigation on small spin systems, e.g. macromolecules, require ultrasensitive devices for sensing the magnetization reversal of such particles with the ultimate goal of single spin flip detection. For this purpose we examine submicron dimension SQUIDs, which can detect the magnetization reversal of small spin particles directly in strong magnetic fields. We fabricated dc SQUIDs based on Nb/HfTi/Nb Josephson junctions with areas down to 200 nm x 200 nm, as well as on YBa₂Cu₃O₇ (YBCO) grain boundary junctions (GBJs) with linewidths down to 80 nm. The critical current densities for both types of junctions are relatively large (j_c>10⁵A/cm² at 4.2 K), which provides high critical currents even for submicron sized junctions. The Nb/HfTi/Nb and the YBCO SQUIDs have been characterized by electric transport and noise measurements at low and high fields up to the tesla range, showing low noise performance.