Development of miniature DC SQUID devices for the detection of single atomic spin-flips

We report progress toward a superconducting quantum interference device (SQUID)-based system capable of detecting a few atomic spin-flips. The scaling of the flux sensitivity with SQUID loop dimension of miniature niobium dc SQUID devices is examined and shown experimentally to vary as predicted. Our smallest device, with loop size 3 /spl mu/m/spl times/3 /spl mu/m, is capable of detecting 40 spins in a 1-Hz bandwidth. We address the task of depositing a sample, of nanoscale dimension, within the SQUID loop.