CORRELATIONS AND DISORDER IN ARRAYS OF MAGNETICALLY COUPLED SUPERCONDUCTING RINGS

We have used ultrasensitive susceptibility techniques and scanning Hal l probe microscopy to study arrays of electrically isolated micron-siz ed superconducting rings. The magnetic moments produced by the supercu rrents in these rings are analogous to Ts-g spins, and neighboring rin gs interact antiferromagnetically via their dipolar magnetic fields. W e find that there are significant antiferromagnetic correlations betwe en rings, and effects due to geometrical frustration can be observed. Quenched disorder also plays a significant role,suppressing the develo pment of true long-range order.