DC superconducting quantum interference devices fabricated using bicrystal grain boundary junctions in Co-doped BaFe 2 As 2 epitaxial films

摘要

DC superconducting quantum interference devices (dc-SQUIDs) were fabricated in Co-doped BaFe 2 As 2 epitaxial films on (La, Sr)(Al, Ta)O 3 bicrystal substrates with 30° misorientation angles. The 18 × 8?μm 2 SQUID loop with an estimated inductance of 13 pH contained two3?μm wide grain boundary junctions. The voltage–flux characteristics clearly exhibited periodic modulations with Δ V = 1.4?μV at 14?K, while the intrinsic flux noise of dc-SQUIDs was 7.8 × 10 ? 5?Φ 0?Hz ? 1/2 above 20?Hz. The rather high flux noise is mainly attributed to the small voltage modulation depth which results from the superconductor–normal-metal–superconductor junction nature of the bicrystal grain boundary.