Low-Noise YBa_(2)Cu_(3)O_(7) dc-SQUIDS and Magnetometers Using Step-Edge Junctions

摘要

Superconducting quantum interference devices(SQUlDs)using YBa2Cu3O7step-edge grain boundary junctions on LaAlO3 substrates were fabricated.The Ⅰ-Ⅴ and V-Ф characteristics of these step-junction dc-SQUIDS were studied.A-modulation voltage exceeding 16μV was attained with Ls=60pH at 77K.At 77K,a square washer configuration with inductance L_(s)=150pH yields flux noise of about 5.08×10^(-5)Ф_(0)/√Hz at frequencies above 100Hz,increasing to 1.1×10^(-4)Ф0/√Hz below 1 Hz.The corresponding magnetic field and energy resolution were 270 fT/√Hz and 3.68×10^(-29)J/Hz respectively,above 100 Hz,and increasing to 710 fT/√Hz and 1.8×10^(-28) J/Hz over a signal frequency range to below 1 Hz.