Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session
TT 33.53: Poster
Mittwoch, 28. März 2012, 15:00–19:00, Poster B
Nb/HfTi/Nb nanoSQUIDs with optimized spin sensitivity — •Matthias Rudolph1, Roman Wölbing1, Joachim Nagel1, Matthias Kemmler1, Reinhold Kleiner1, Dieter Koelle1, Oliver Kieler2, Thomas Weimann2, Johannes Kohlmann2, and Alexander Zorin2 — 1Physikalisches Institut and Center for Collective Quantum Phenomena in LISA+, Universität Tübingen, 72076 Tübingen, Germany — 2Fachbereich 2.4 , Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany
Nowadays the downscaling of SQUIDs to the submicron range is mainly motivated by applications for magnetization measurements of small magnetic systems like single magnetic molecules. We use SQUIDs based on Nb/HfTi/Nb junctions, which do not require bulky resistive shunts. The parameters of the junctions can be optimized for flux sensitive SQUIDs and the used nanolithography technique (e-beam) allows the realization of SQUID loops in the submicron range and junction sizes on the order of 100 nm. For some SQUIDs we implemented coils on the chip that are galvanically coupled to the SQUID loop. These coils allow to modulate the SQUIDs without the need of external coils with relatively small currents. This might be useful for the flux-locked operation of our SQUIDs using conventional SQUID electronics.
We present a detailed study of the transport properties and the flux noise characteristics of several SQUIDs with different designs (magnetometer-type or gradiometric) in low magnetic fields as well as magnetic fields up to 100 mT. For our best SQUID geometries we obtain a spin sensitivity Sµ1/2=29 µB/Hz1/2.