High Sensitive Magnetic Nanosensors Based on Superconducting Quantum Interference Device

Nanosized superconducting quantum interference devices (nano-SQUIDs) offer the possibility to investigate small spin populations and the magnetization of nanoparticles opening new horizons in the world of nanomagnetism. We will report recent results about the design, the fabrication and the characterization of high sensitive magnetic nanosensors based on nano-SQUID having a flux capture area of 0.5 μm². In order to achieve a better magnetic flux resolution a proper device design has been developed. The fabrication process is based on the electron beam lithography and a lift-off procedure in a 25 nm thick Nb layer. Measurements of current-voltage and current vs. magnetic flux characteristics have been reported. The comparison between the nanodevice based on the improved design and a standard one has shown the effectiveness of the new design. Preliminary measurements at T=4.2 K on Fe₃O₄ nanoparticles having a size of 8 nm have been reported, showing the capability of such nanodevices to investigate the magnetism at a submicrometric scale.