Regensburg 2013 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 49: Superconductivity: SQUIDs & Cryodetectors
TT 49.2: Talk
Wednesday, March 13, 2013, 17:15–17:30, H21
Nb nanoSQUIDs for detection of small spin systems — •R. Wölbing1, J. Nagel1, M. Kemmler1, R. Kleiner1, D. Koelle1, O. Kieler2, T. Weimann2, J. Kohlmann2, A. Zorin2, A. Buchter3, F. Xue3, M. Poggio3, D. Rüffer4, E. Russo-Averchi4, A. Fontcuberta i Morral4, R. Huber5, P. Berberich5, and D. Grundler4,5 — 1Physikalisches Institut, Universität Tübingen, Germany — 2Fachbereich 2.4 "Quantenelektronik", PTB Braunschweig, Germany — 3Department of Physics, University of Basel, Switzerland — 4Laboratoire des Matériaux Semiconducteurs, EPF Lausanne, Switzerland — 5Physik-Department E10, Technische Universität München, Germany
We report on the realization of highly sensitive dc nanoSQUIDs for the investigation of small spin systems in moderate magnetic fields. The Nb SQUIDs are based on normal metal Josephson junctions made of HfTi and patterned by e-beam lithography. We demonstrate stable operation up to B=±50 mT without degradation of rms flux noise (SΦ1/2≤280 nΦ0/√Hz). We also present a multifunctional system combining a Nb nanoSQUID and a low-temperature magnetic force microscope (LTMFM) with a Ni nanotube as a scanning tip. This system allows for magnetization measurements of the Ni tube by using both, LTMFM and SQUID readout. Furthermore, the measurement of magnetic flux Φ vs. position of the particle provides an experimental determination of the coupling factor φµ=Φ/µ between SQUID and Ni tube with magnetic moment µ. The results confirm our predictions from numerical simulations, taking into account the SQUID geometry.