Higher Order HTSC Gradiometer for Measurements in Unshielded Environment

We present a new higher order gradiometer layout for bicrystal Josephson junctions based on high-temperature superconducting thin films. Our single layer gradiometers are suitable for the simultaneous measurement of magnetic field gradients with different spatial orientations. The sophisticated technology for bicrystal Josephson junctions is combined with custom substrates with two crossing 30 degree grain boundaries. We present the technological challenges focusing on the low ohmic contact resistance using gold nanoparticles embedded in the thin film. The sensor performance is characterized using SQUID electronics. Its main parameters such as critical current and ICRN-product are compared with parameters of first order gradiometers on single 30 degree bicrystal substrates. Special emphasis is put on the optimization of the noise properties in unshielded environment.