A highly sensitive YBCO serial SQUID magnetometer with a flux focuser

Abstract

We have designed and fabricated a low noise, high T c superconducting quantum interference device (SQUID) magnetometer with an improved yield. In order to reduce the field noise level of the magnetometer, we increased the voltage modulation depth with a series SQUID array and enhanced the effective area with a flux focuser. Ten washer-type SQUIDs were connected in series, thereby increasing the voltage flux transfer function by a factor of 10. An enhancement in effective area by a factor of 5 was achieved by coupling the 10-SQUID array to a single-layered flux focuser. For the directly coupled SQUID array magnetometer, the yield was improved by selecting the best SQUIDs to have in series in order to reduce the flux noise. The magnetic field sensitivity of 40 fT Hz −1/2 in the white regime and 100 fT Hz −1/2 at 1 Hz is demonstrated by using a single layer of high T c film. The proposed high yield magnetometers would be suitable for building low noise multi-channel magnetocardiographs.

2D SQIF arrays using 20 000 YBCO highRnJosephson junctions

“…HTS arrays, the subject of this letter, have instead been limited by the junctions technologies used. The scalability of the number of HTS junctions was initially examined using series arrays of loops for improving device sensitivity [14] and voltage output [15][16][17] to enable matching to room temperature pre-amplifiers. In the early 2000s Oppenlander et al [18] proposed arrays with a range of loop areas, termed superconducting quantum interference filters or SQIFs.…”

Superconducting epitaxial $$\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\delta }$$ YBa 2 Cu 3 O 7

“…Efforts to elucidate the microscopic mechanism governing superconductivity in the cuprates have improved our fundamental understanding of strongly correlated phenomena in condensed matter systems [1]. With regard to technological importance, cuprate materials such as YBa 2 Cu 3 O 7−δ (YBCO) were explored for potential use in applications such as infrared detectors, microwave filters and superconducting quantum interface devices (SQUID) [2][3][4][5][6][7][8]. For many applications, high transition temperatures (T c ) and narrow transition widths are desired, and thus, single crystalline films are preferred [9,10].…”