Making SQUIDs a practical tool for quantum detection and material characterization in the micro- and nanoscale

Abstract

The investigation of quantum effects and materials at low and ultra-low temperature often requires very sensitive measurements of weak magnetic signals, small electric currents or voltages. Superconducting Quantum Interference Devices (SQUIDs) have been proven as very attractive tools in this field. However, well established fabrication technology and readout techniques usually fail, particularly, when going to nanoscale magnetic detection where off- the-shelf devices can rarely be used. As an alternative to elaborate nanoSQUID technology, SQUID concepts for nanoscale magnetic detection which are employing conventional, and hence, reliable technology are discussed. Magnetic coupling of nano-sized samples to conventional SQUIDs, e.g. simple gradiometers or more complex devices as fully integrated susceptometers, can be improved significantly by integrating nanoscale detection loops into these devices. Furthermore, appropriate SQUID current sensors are a prerequisite for the readout of micro- and nanoSQUIDs and small-area detection coils. The conventionally made devices are intended for fabrication in moderate numbers to make them available for a broader community.