Squid Sensors for High Spatial Resolution Magnetic Imaging and for Nanoscale Applications

Abstract

We present the improved Superconducting Quantum Interference Devices (SQUID) for magnetic microscopy and for nanoscale investigations. Low critical Temperature SQUIDs with integrated micro pick-up coils (with inner diameter ranging from 5 to 50 μm) which can be used as magnetic field sensors in magnetic microscopy have been developed. The level of flux noise spectral density, measured in flux locked loop configuration and using a direct coupled scheme, is about $3\mu\Phi_{0}/\surd{Hz}$ in the white region at T = 4.2 K.

A high sensitive dc-SQUID based on niobium Dayem bridges for nanomagnetism is presented. The sensor has a flux capture area as low as 0.04 μm², allowing the study of nano–object magnetic properties. The authors report the main design rules of the devices, the fabrication processes and their characterization including also the supercurrent decay measurements at T = 4.2 K.