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.