Showing papers by "Keiji Enpuku published in 1998"
TL;DR: In this paper, the relationship between the junction properties and the misorientation angle of the bicrystal substrate is studied experimentally, and the angular dependencies of junction resistance Rs and critical current Io are investigated.
Abstract: In order to develop YBa2Cu3O7-δ bicrystal junctions suitable for high-performance superconducting quantum interference device (SQUID), the relationship between the junction properties and the misorientation angle of the bicrystal substrate is studied experimentally. Misorientation angles of 24°, 27°, 30°, 33° and 36.8° are used, and the angular dependencies of junction resistance Rs and critical current Io are investigated. It is shown that values of Rs and Io approximately follow the relation IoRs1.5=const. in these junctions. The obtained results are analyzed in terms of the direct and resonant tunneling mechanisms. It is also shown that values of Rs≈10 Ω and Io≈20 µA can be obtained rather reproducibly when we use the 30° junctions. The properties of this junction are very promising for the development of high-performance SQUID.
19 citations
TL;DR: In this paper, a comprehensive quantitative comparison between the measured performance of direct-coupled high Tc superconducting quantum interference device (SQUID) magnetometers with 30° bicrystal junctions and a numerical simulation is presented.
Abstract: A comprehensive quantitative comparison between the measured performance of direct-coupled high Tc superconducting quantum interference device (SQUID) magnetometers with 30° bicrystal junctions and a numerical simulation is presented. It is shown that the characteristics of the SQUID magnetometer are considerably affected by resonances due to the large dielectric constant of the SrTiO3 substrate. In the realized magnetometer layout, the strip line resonance occurring in the SQUID inductance increases the voltage modulation depth and the output voltage noise of the SQUID, while the flux noise of the SQUID is nearly unchanged. It is also shown that the distortion of the voltage versus flux characteristic is caused by the LC resonance in the pickup loop of the magnetometer in combination with a capacitive feedback. Good agreement between experiment and simulation has been obtained.
7 citations
01 Jan 1998
TL;DR: In this article, a high performance high T c dc SQUID was fabricated using a bicrystal junction with a misorientation angle of θ=30°, which exhibited voltage modulation depths as high as ΔV=85 µV, 50 µV and 20 µV at T=77 K for the inductance values of L s=60 pH, 100 pH and 160 pH, respectively.
Abstract: A high performance high T c dc SQUID was fabricated using a bicrystal junction with a misorientation angle of θ=30°. The bicrystal junctions showed junction resistance R s=10 Ω and critical current I o=25 µA (I o R s =250 µV) at T=77K when junction width is w=2 µm. The SQUID exhibited voltage modulation depths as high as ΔV=85 µV, 50 µV and 20 µV at T=77 K for the inductance values of L s=60 pH, 100 pH and 160 pH, respectively. Preliminary noise measurement showed that the flux noise of the SQUID is less than 10µΦo /Hz1/2 in the white noise region for the case of L s=100 pH. These results indicate that the bicrystal junction with a misorientation angle of θ=30° has great potential for the development of high performance SQUIDs.