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.
Josephson junctions and superconducting quantum interference devices made by local oxidation of niobium ultrathin films
