High <i>T</i> <i>c</i> superconductor-normal-superconductor step-edge junction dc SQUIDs with CaRuO3 as the normal metal

Abstract

Superconductor-normal-superconductor (SNS) type step-edge junction dc SQUIDs were fabricated from YBa2Cu3O7−δ (YBCO) films with CaRuO3 as the normal metal by pulsed laser deposition and Ar+ beam patterning techniques. CaRuO3 films were grown epitaxially on YBCO and had a metallic conduction property. Current-voltage curves of the junctions showed a resistively shunted-junction behavior. Temperature dependence of the junction critical current was linear in agreement with the theory for junctions with the junction length shorter than twice of the normal coherence length (dN&amp;lt;2ξN). A well-behaving SQUID modulation signal was observed up to 52 K with a focusing parameter of 8.6.