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TT: Fachverband Tiefe Temperaturen

TT 49: Superconductivity: SQUIDs & Cryodetectors

TT 49.3: Vortrag

Mittwoch, 13. März 2013, 17:30–17:45, H21

Low-noise YBa₂Cu₃O₇ nanoSQUIDs for the detection of small spin systems operating in Tesla magnetic fields — •Tobias Schwarz, Joachim Nagel, Roman Wölbing, Reinhold Kleiner, and Dieter Koelle — Physikalisches Institut - Experimentalphysik II and Center for Collective Quantum Phenomena in LISA⁺, Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany

We investigated the noise performance of YBa₂Cu₃O₇ (YBCO) nanoSQUIDs with grain boundary Josephson junctions in high magnetic fields. On SrTiO₃ [001] bicrystal substrates YBCO films were grown by pulsed laser deposition and covered by an in-situ evaporated gold layer to provide non-hysteretic IV-curves. SQUIDs with line widths down to 100nm were fabricated by focused ion beam milling. A constriction next to the SQUID allows on-chip modulation of the magnetic flux coupled into the SQUID loop. The SQUID we present here can be operated in Tesla magnetic fields applied parallel to the SQUID loop. The white flux noise level increases only slightly from S_Φ^1/2= 1.3 µ _B/Hz^1/2 at B=0 to S_Φ^1/2= 2.3 µ Φ ₀ Φ ₀/Hz^1/2 at B=1T. Assuming that a point-like magnetic particle is placed on top of the constriction, we calculate a spin sensitivity S_µ^1/2= 62 µ _B/Hz^1/2 at B=0 and S_µ^1/2= 110 µ _B/Hz^1/2 at B=1T. Further we show that by optimizing the parameters of the presented SQUID geometry spin sensitivities of a few µ _B/Hz^1/2 should be feasible.