Characteristics of NdBa₂Cu₃O_7-δ/PrBa₂Cu₃O_7-δ/NdBa₂Cu₃O_7-δPlanar Josephson Junctions

Abstract

We report on the well-characterized properties of a-axis oriented trilayer Josephson junctions made of NdBa2Cu3O7-δ and PrBa2(Cu,Co)3O7-δ films, and c-axis oriented trilayer Josephson junctions made of NdBa2Cu3O7-δ and PrBa2Cu3O7-δ films with smooth surface morphology and good crystallinity. a-Axis oriented NdBa2Cu3O7-δ/PrBa2(Cu,Co)3O7-δ/NdBa2Cu3O7-δ trilayers and c-axis oriented NdBa2Cu3O7-δ/PrBa2Cu3O7-δ/NdBa2Cu3O7-δ trilayers were prepared on (100) SrTiO3 substrates to obtain planar junctions. Their current–voltage characteristics are of the resistively-shunted-junction type at 4.2 K. They showed well-developed Shapiro steps corresponding to 5–20 GHz microwave irradiation. Moreover, the power dependences of the maximum amplitudes of the Shapiro steps were clearly obtained and consistent with the theoretical values expressed as Jn(2eV/hf). The magnetic field dependence of the Josephson current for a-axis oriented trilayer Josephson junctions showed a Fraunhofer-like pattern, suggesting the spatial uniformity of the critical current flowing over the PrBa2(Cu,Co)3O7-δ barrier layer.