Comparison of High Temperature Superconducting Gradiometers Using Flip Chip YBCO and TBCCO Antennas

To optimize our high-temperature superconducting (HTSC)-dc-SQUID gradiometric sensors with galvanically-coupled antennas, we investigated the performance of antennas on a separate substrate. These antennas are inductively coupled to a dc-SQUID-gradiometer in a flip-chip configuration. Different combinations of thin-film and substrate materials, including Tl 2 Ba 2 CaCu 2 O 8 _ x (TBCCO) on Al 2 O 3 or LaAlO 3 and YBa 2 Cu 3 O 7-x (YBCO) on SrTiO 3 , were used to produce antennas with variable layouts. These were then characterized concerning their critical current densities, critical temperature, and noise properties to demonstrate their suitability for high-resolution magnetic measurements in a flip-chip configuration. Field gradient resolution and noise properties of multiple dc-SQUID gradiometer antenna combinations were determined and compared.