2010/09/14 by J. Nagel, K. B. Konovalenko, Nagel, J. +19
Physics and Astronomy · #FOS: Physical sciences #Magnetic properties of thin films #Physics of Superconductivity and Magnetism #Quantum and electron transport phenomena #Superconductivity (cond-mat.supr-con) #cond-mat.supr-con
paper · pdf · doi:10.48550/arxiv.1009.2657
arxiv created 2010/09/14 · openalex publication_date 2010/09/14 · arxiv updated 2010/09/15 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
YBa2Cu3O7 24^∘ (30^∘) bicrystal grain boundary junctions (GBJs), shunted with 60 nm (20 nm) thick Au, were fabricated by focused ion beam milling with widths 80 \rm nm ≤ w ≤ 7.8 μm. At 4.2 K we find critical current densities jc in the 105 \rm A/cm2 range %\dkc#1 (without a clear dependence on w) and an increase in resistance times junction area ρ with an approximate scaling ρ∝ w1/2. For the narrowest GBJs jcρ≈ 100 μV, which is promising for the realization of sensitive nanoSQUIDs for the detection of small spin systems. We demonstrate that our fabrication process allows the realization of sensitive nanoscale dc SQUIDs; for a SQUID with w≈ 100 nm wide GBJs we find an rms magnetic flux noise spectral density of SΦ1/2≈ 4 μΦ0/\rm Hz1/2 in the white noise limit. We also derive an expression for the spin sensitivity Sμ1/2, which depends on SΦ1/2, on the location and orientation of the magnetic moment of a magnetic particle to be detected by the SQUID, and on the SQUID geometry. For the not optimized SQUIDs presented here, we estimate Sμ1/2=390 μB/√\rmHz, which could be further improved by at least an order of magnitude.