High-temperature superconducting pickup-loop hysteresis for magnetometer and gradiometer configurations

Magnetic hysteresis of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin-film pickup loops was measured using a single-layer sample design that allowed experiments to characterize both magnetometers and gradiometers. Measurements were performed at 77 K for samples having pickup-loop linewidths ranging from 20 /spl mu/m to 800 /spl mu/m. Magnetometer hysteresis was found to increase with increasing linewidth and increasing amplitude of the applied magnetic field ramp. Gradiometer hysteresis was found to depend primarily on the degree of hysteretic balance between the two individual loops comprising the gradiometer. The dependence of gradiometer hysteresis on applied field amplitude was found to be sample dependent, monotonically increasing in some cases, and exhibiting a local minimum in others.