INVESTIGATION OF THIN-FILM DE SQUID GRADIOMETER USING A SINGLE YBCO LAYER

Thin film dc SQUID gradiometers with a large effective pickup area usi ng only a single YBa2Cu3O7-x layer and step edge Josephson junctions o n SrTiO3 substrate have been prepared. The planar gradiometer consist of two loops coupled directly to a small area SQUID in the renter of t he structure. The main advantage in comparison to magnetometers is the possibility of direct measurements in magnetically unshielded environ ment. At 77 K without bias reversal technique we obtain a white noise level about 3.610(-5) Phi(0)/Hz(1/2) or 700 fT/cmHz(1/2). Some peculi arities for two SQUID arrangement with 4 Josephson junctions are obser ved and simulated on the base of RSJ model.