Fabrication and characterization of high-Tc SQUID magnetometer with damping resistance

Effects of damping resistance on current versus voltage (I-V) characteristics for high-T_c superconducting quantum interference devices (SQUIDs) were studied. In the transverse-type SQUID with coplanar strip lines, parasitic capacitance originating from the large dielectric constant of SrTiO₃ substrates can induce resonance structures on I-V curves and degrade the modulation voltage. In our simulations, it is shown that the modulation voltage is much improved by using damping resistance. However, the obtained experimental results for our SQUIDs with Au damping do not agree well with those in the simulations. The discrepancy is likely due to existence of the large contact resistance between Au and YBa₂Cu₃O_7-δ films.