Millimeter Wave Study of Hybrid Superconducting Heterostructures with Magnetic Active Interlayer

We fabricated Nb/Au/(Ca 1-x Sr x )CuO 2 /YBa 2 Cu 3 O 7 superconducting heterostructures with I C RN product 100divide300 muV at T=4.2 K. Critical current density was 10 A/cm 2 through 50 nm thick Ca 1-x Sr x CuO 2 layer, and increased for thinner layers. Critical currents of the heterostructures had much smaller periods in l c (H) dependencies compare to Josephson junctions without anti ferromagnetic layer. Half- integer Shapiro steps and detector responses were observed for the most of heterostructures. Current phase relations of the heterostructures deviated from sinusoidal with 10divide40% portion of the second harmonic.