SQUID magnetometer noise measurements on YBa/sub 2/Cu/sub 3/O/sub 7/ thin films and input coils

A SQUID magnetometer system incorporating a NB-based conventional SQUID operating at 4.8 K was used to measure the magnetic field noise from high-T/sub c/ input coils and unpatterned films at 77 K. The system allows for the rapid measurement of relatively large regions of high-T/sub c/ material. The results on numerous coils and films show the noise decreasing as a function of increasing film critical current density at 77 K. High-T/sub c/ films with J/sub c/(77 K)=3*10/sup 6/ A/cm/sup 2/ appear suitable for use as input coils in SQUID magnetometer applications requiring low noise at frequencies down to 1 Hz.