Noise properties of HTS flux transformers fabricated by chemical-mechanical polishing
Conference contribution, 2011
We present on fabrication and noise properties of high-temperature superconducting (HTS) thin-film integrated multilayer flux transformers fabricated using planarization of YBCO films by chemical-mechanical polishing (CMP). The polishing allows fabrication of very shallow slope edges (less than 5°) in the YBa2Cu3O7, that makes it possible to avoid formation of grain boundary junctions in crossovers and obtain very high critical current densities in the top electrode of about 2•106 A/cm2. The same planarization process is used to create interconnections between top and bottom superconducting electrodes through the SrTiO3/PrBa2Cu3O7/SrTiO3 insulating layer. HTS multilayer flip-chip flux transformer with 8x8 mm2 pickup loop and 20-turn input coil was fabricated and coupled to a bicrystal dc SQUID in a flip-chip configuration. We measured magnetic field gain of 1.2 nT/Ф0 and magnetic flux noise of the magnetometer 10 µФ0/√Hz at 1 kHz, which corresponds to magnetic field noise of 12 ft/√Hz. FLUX NOISE AT LOW FREQUENCIES! The work is supported by European FP7 project "MEGMRI" under contract number 200859.