MgB₂magnetometer with a directly coupled pick-up loop

Abstract

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.

Micro-SQUIDs based on MgB2nano-bridges for NEMS readout

“…Similarly for D2, with I c (4.2 K)≈0.8 mA and A=1.1×10 −11 cm 2 , we calculate J c ≈3.5×10 7 A cm −2 . The J c value of D2 sample results comparable to one obtained in references [4,5], whereas the D1 device shows a higher current density value, like that reported in [20].…”

“…The relatively high superconducting critical temperature of magnesium diboride (T c =39 K) and its intermetallic properties makes MgB 2 a suitable material to fabricate superconductor quantum interference device (SQUID) [1]. For more than a decade, MgB 2 SQUIDs have been successfully fabricated and studied by several groups [2][3][4][5][6][7]. Nowadays, MgB 2 -based SQUIDs are developed instruments for practical applications [8] and have been integrated into experimental systems, such as for magnetocardiography [9].…”

“…The idea behind this work has the purpose of realising magnetometers, which allow optimised coupling between SQUID-readout and NEMS, combined with relatively high operating temperature. In order to reach this goal we fabricated micro-ring structured SQUIDS on very thin epitaxial films, while still maintaining good superconducting properties, and we reduced the constriction dimensions to less than 100 nm, like in [2][3][4][5][6][7]. The first technique will allow etching by using ion milling instead of focused ion beam, avoiding eventually Ga ion implantation.…”

ISEC 2005—Conference summary and comments on SQUIDs and coolers

“…However the first promising results of their application for superconducting digital devices are leading to improved stability due to stronger immunity against fabrication spread and noise during operation [27] and may in turn lead to new sensor concepts. SQUIDs using MgB 2 thin films are being developed [28] but as of now there is no ready alternative to standard materials. 1 Tristan Technologies, Inc., San Diego, USA.…”

Fabrication of superconducting MgB2nanostructures

“…In fact they can act as weak-links in superconducting devices, e.g. SQUIDs [1][2][3][4] or superconducting nanotransistors (SNTs) [5]. Possible applications of MgB 2 nanostructures in superconducting single-photon detectors (SNTDs) could also be investigated.…”