scholarly journals Evaluation of Self-Field Effects in Magnetometers Based on Meander-Shaped Arrays of Josephson Junctions or SQUIDs Connected in Series

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1588
Author(s):  
Denis Crété ◽  
Julien Kermorvant ◽  
Yves Lemaître ◽  
Bruno Marcilhac ◽  
Salvatore Mesoraca ◽  
...  

Arrays of superconducting quantum interference devices (SQUIDs) are highly sensitive magnetometers that can operate without a flux-locked loop, as opposed to single SQUID magnetometers. They have no source of ambiguity and benefit from a larger bandwidth. They can be used to measure absolute magnetic fields with a dynamic range scaling as the number of SQUIDs they contain. A very common arrangement for a series array of SQUIDs is with meanders as it uses the substrate area efficiently. As for most layouts with long arrays, this layout breaks the symmetry required for the elimination of adverse self-field effects. We investigate the scaling behavior of series arrays of SQUIDs, taking into account the self-field generated by the bias current flowing along the meander. We propose a design for the partial compensation of this self-field. In addition, we provide a comparison with the case of series arrays of long Josephson junctions, using the Fraunhofer pattern for applications in magnetometry. We find that compensation is required for arrays of the larger size and that, depending on the technology, arrays of long Josephson junctions may have better performance than arrays of SQUIDs.

Author(s):  
M.J. Martínez-Pérez ◽  
R. Kleiner ◽  
D. Koelle

This article discusses the use of nanoSQUIDs for investigating small magnetic systems. It begins with an overview of the basics of superconducting quantum interference devices, focusing on how a dc SQUID operates and the use of resistively and capacitively shunted junction model to describe the phase dynamics of Josephson junctions (JJs). It then considers the motivation for using nanoSQUIDs, along with the importance of their size and geometry. It also evaluates micro- and nanoSQUIDs made of various types of JJs including nanoSQUIDs based on sandwich-like junctions, constriction-like junctions, and proximized structures. After reviewing different nanoSQUID readout methods that can be used to directly sense the stray magnetic field created by a nanoscale magnetic sample, the article concludes by highlighting some of the practical constraints and challenges encountered in using nanoSQUID technology, including particle positioning with respect to the sensor’s surface.


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