Miniature DC SQUID devices for the detection of single atomic spin-flips: scaling of flux sensitivity with device dimension

We report progress towards a SQUID based system capable of detecting single 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 a few spins in a 1 Hz bandwidth.