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Readout system for NanoSQUID sensors using a SQUID amplifier.

Ruede, F*; Bechstein, S*; Hao, L; Assmann, C*; Schurig, T*; Gallop, J C; Kazakova, O; Beyer, J*; Drung, D* (2011) Readout system for NanoSQUID sensors using a SQUID amplifier. IEEE Trans. Appl. Supercond., 21 (3). pp. 408-411.

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NanoSQUID sensors are regarded as a useful tool for sensitive magnetic measurements at the nanoscale, e.g. detection of individual magnetic nanoparticles, and have achieved a low noise level which could potentially lead to detection of a single electron spin. The nanoSQUIDs (loop size 250 ~ 800 nm) are processed by photolithography and focused ion beam patterning of a simple bilayer.
In contrast to common SQUID sensors, the fabrication and read-out of nanoSQUIDs is quite challenging. The technological obstacles for the preparation of junctions and shunt resistors with nm-dimensions make the self-shunted nanobridge junctions attractive. However, self-shunted nanobridge junctions have shown hysteretic characteristics at 4.2 K. An approach is to increase the operational temperature in order to reduce the critical current of the device.
The small sensing area of nanoSQUIDs and its correspondingly low sensitivity to external magnetic fields hamper the application of common feedback schemes. For detection of a magnetic nanoparticle attached to the SQUID, an additional magnetic field for aligning the magnetic moment of the particle is required.
We report the design and construction of an evacuated liquid helium cooled probestick with rf-shield, coil system, and SQUID preamplifier to read out the voltage-biased nanoSQUID. Some initial experimental results will be presented.

Item Type: Article
Keywords: NanoSQUID, SQUID-Amplifier
Subjects: Quantum Phenomena
Quantum Phenomena > Nanophysics
Identification number/DOI: 10.1109/TASC.2010.2089483
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/5043

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