A Directly Coupled Superconducting Quantum Interference Device Magnetometer Fabricated in Magnesium Diboride by Focused Ion Beam

摘要

We report the fabrication of a directly coupled superconducting quantuminterference device (SQUID) magnetometer in MgB2 using a focused ion beam (FIB)to create Josephson junctions in a 70 nm thick film of MgB2. The SQUID shows avoltage modulation (deltaV) of 175 mV at a temperature of 10 K and operatesover a temperature range from 10 K to 24 K. We find excellent agreement betweenthe measured maximum transfer functions and those predicted by theory. We havemeasured the magnetic flux noise at 20 K to be as low as 14 micro Phi-0 perroot Hz.