MgB2magnetometer with a directly coupled pick-up loop

In this work, we show the results obtained in the fabrication and characterization of an MgB 2 magnetometer with a directly coupled pick-up loop. We used an all in situ technique for fabricating magnesium diboride films, which consists of the co-evaporation of B and Mg by means of an e-gun and a resistive heater respectively. Consequently, we realized the superconducting device, which incorporates two nanobridges as weak links in a superconducting loop. The nanobridges were realized by focused ion beam milling; they were 240 nm wide and had a critical current density of 10 7 A cm −2 . The magnetometer was characterized at different temperatures and also measurements of the noise levels have been performed. The device shows Josephson quantum interference up to 20 K and the calculated effective area at low temperatures was 0.24 mm 2 . The transport properties of the magnetometer allow determining fundamental materials properties of the MgB 2 thin films, such as the penetration depth.