Further investigations on dc-SQUID gradiometers based on growth modified bi-crystal grain boundaries

The properties of grain boundaries of YBa2Cu3O7-δ (YBCO) films grown on bi-crystal substrates can be modified by gold nano crystallites self-assembling from an intermediate gold layer during pulsed laser deposition. These gold particles act as additional pinning centers in the YBCO layer. Using a new layout, which enables us to restrict the gold nano crystallites only to the Superconducting QUantum Interference Device (SQUID) or the antenna structures, we fabricated dc-SQUID gradiometers. We present results of the temperature dependence of the London penetration depth as well as of noise measurements carried out with ac- and dc-bias. In addition we investigated the dependence of the superconducting properties on the thickness of the initial gold layer.