Superconductivity News Forum (SNF)
Annotated Presentation, PDFHfTi-nanoSQUIDs for Nanoscale Magnetic Detection
Sylke Bechstein1, Claudia Köhn1, Jan-Hendrik Storm1, Dietmar Drung1, Marianne Fleischer-Bartsch1, Oliver Kieler2, Johannes Kohlmann2, Thomas Weimann2, and Thomas Schurig1
1Physikalisch-Technische Bundesanstalt, (PTB), Abbestraße 2-12, 10587 Berlin, Germany
2Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany
2Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany
E-mail: [email protected]
Abstract — As recently reported [1], we have developed different types of Nb/HfTi/Nb-nanoSQUIDs with a lateral junction size of about 200 nm x 200 nm and an inner loop size of about 840 nm x 840 nm. These nanoSQUIDs were designed as gradiometers, and implemented with gradiometric feedback loops, gradiometric transformers and rf filters to enhance their practical use. The noise in the white frequency range depends on the SQUID loop inductance, and is typically 115 nΦ0/√Hz for parallel nanoSQUID gradiometers, or about 200 nΦ0/√Hz for series nanoSQUID gradiometers. In combination with a SQUID series array which acts as a low-noise preamplifier, these nanoSQUIDs can be operated in the flux locked loop mode with high linearity in an ac magnetic field of up to a few mT. In this configuration, the excitation field is orientated either perpendicular or in-plane to the gradiometric SQUID loop. That is an experimental setup used e.g. for particle investigations. For the readout of nano-electromechanical resonator systems (NEMS), the field tolerance to a dc in-plane magnetic field is of considerable interest. We demonstrate the operation in dc in-plane fields of a few tens of mT with several measurements – most of them performed in a two-stage configuration. Finally, we present an experimental setup for NEMS readout which has been developed for investigation of nanoSQUID-NEMS combinations.
[1] S. Bechstein et al., ‘HfTi-nanoSQUID gradiometers with high linearity, ‘Appl. Phys. Lett. 106, 072601 (2015), doi 10.1063/1.4909523.
This work was partly supported by the DFG under Grant No. SCHU1950/5-1 and within the European Metrology Research Programme EMRP ‘MetNEMS’ NEW-08, which is jointly funded by the participating countries within EURAMET and the European Union.
Keywords (Index Terms) — NanoSQUID, linearity, flux noise, magnetic field tolerance.
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), January 2016.
Received October 19, 2015, Selected December 18, 2015. Reference No. STP498; Category 4.
KRYO 2015 oral presentation. Not submitted for publication.
Received October 19, 2015, Selected December 18, 2015. Reference No. STP498; Category 4.
KRYO 2015 oral presentation. Not submitted for publication.