Berlin 2015 – wissenschaftliches Programm
TT 21.43: Poster
Montag, 16. März 2015, 15:00–18:00, Poster B
Sensitive YBCO nanoSQUIDs for the investigation of small spin systems — •Benedikt Müller1, Tobias Schwarz1, Roman Wölbing1, María José Martínez-Pérez1, Christopher F. Reiche2, Thomas Mühl2, Bernd Büchner2, Reinhold Kleiner1, and Dieter Koelle1 — 1Physikalisches Institut and Center for Collective Quantum Phenomena in LISA+, Universität Tübingen, Auf der Morgenstelle 14, 72076 Tübingen, Germany — 2Leibniz Institute for Solid State and Materials Research IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
We report on advances in the realization of dc YBCO nanoSQUIDs for continuous measurement of magnetic nanoparticle magnetization loops in strong magnetic fields up to the Tesla range, applied in the plane of the SQUID loop at temperatures of 4 K and below. Our grain boundary junction based YBCO SQUIDs are patterned by focused ion beam milling and feature a constriction next to the SQUID loop, allowing for on-chip SQUID modulation and bias reversal readout schemes.
Using numerical simulations based on London theory, the spin sensitivity Sµ1/2 = SΦ1/2 / φµ was improved by optimizing both the flux noise SΦ1/2 and the coupling factor φµ= Φ / µ (Φ is the magnetic flux coupled into the SQUID loop by a particle with magnetic moment µ). For optimized experimental devices, flux noise levels down to 50 nΦ0 / Hz1/2 in the white noise limit have been achieved, corresponding to a calculated spin sensitivity of only a few µB / Hz1/2.
Further, the magnetization reversal of a Fe filled carbon nanotube attached to a YBCO nanoSQUID was traced out.