A TlBaCaCuO Thin Film Planar dc-Squid Magnetometer

A superconducting quantum interference device (squid) was made from TlBa-CaCuO(TBCCO) thin film. The squid loop forms a part of the pickup loop. The squid hole is a square of about 100x100μm. The pickup loop and the squid loop inductances are estimated to be 11 nH and 190pH, respectively. The best value of equivalent flux noise as measured in the flux locked loop mode is 4x10^-4 Ф₀ / Hz^1/2 at dc-1 Hz. The corresponding sensitivity resolution at this frequency is 9pT/Hz^1/2, about a factor 8 higher than the squid loop area.