Four-channel YBa2Cu3O7−<i>y</i> dc SQUID magnetometer for biomagnetic measurements

Tanaka, Saburo; Itozaki, Hideo; Toyoda, Haruhisa; Harada, N.; Adachi, Akira; Okajima, Kenichi; Kado, H.; Nagaishi, Tatsuoki

doi:10.1063/1.111090

Cited by 32 publications

(10 citation statements)

References 8 publications

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“…Thus, if one wishes to limit the total inductance to 40 pH, the maximum washer size is 200 m even if there is no hole (dϭ0) as in type A/A. In contrast, for types B or C, the inductance is approximately L h , independent of the washer size D. However, the effective area A eff is significantly less than dD for D ӷd, because of the focusing of flux into the slits outside the SQUID loop Tanaka et al, 1994). The latter effect is minimized in type A/C: for example, for Dϭ500 m and Lϭ40 pH one finds A eff Ϸ0.015 mm 2 , roughly a factor of two larger than for type B or C with the same values of D and L or for a 40-pH type A/A SQUID (Ludwig, Dantsker, Koelle, Kleiner, Miklich, Nemeth et al, 1995).…”

Section: A Square-washer Designsmentioning

confidence: 99%

“…For example, with A eff ϭ0.015 mm 2 and S ⌽ 1/2 ϭ10 ⌽ 0 /Hz Ϫ1/2 one finds S B 1/2 ϭ1.3 pT/Hz Ϫ1/2 well above the resolution of 10-100 fT/Hz Ϫ1/2 typically required. However, larger washers Tanaka et al, 1994) have achieved a magnetic-field noise of about 150 fT/Hz 1/2 at 1 kHz and 500 fT/Hz 1/2 at 1 Hz with SQUID inductances of 40-100 pH and washers of 5-11 mm. Comparable performance has been achieved with fluxfocusing plates of similar size coupled to washer SQUIDs 2ϫ2 mm 2 in size Itozaki et al, 1996).…”

Section: A Square-washer Designsmentioning

confidence: 99%

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High-transition-temperature superconducting quantum interference devices

et al. 1999

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Section: A Square-washer Designsmentioning

confidence: 99%

Section: A Square-washer Designsmentioning

confidence: 99%

High-transition-temperature superconducting quantum interference devices

et al. 1999

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“…Traditionally, SQUIDs have been employed as extremely sensitive magnetic-field sensors in biomagnetometry, e.g., magnetoencephalography and magnetocardiography. Whereas the former has already been demonstrated successfully with high-T c SQUIDs (Curio et al, 1996;Drung, Dantsker, et al, 1996), there is particularly strong interest in employing high-T c SQUIDs in the latter (Tanaka et al, 1994;Burghoff et al, 1996;Drung, Dantsker, et al, 1996;. An appealing prospect is the use of high-T c bicrystal SQUIDs for fetal magnetocardiography (Rijpma et al, 1999).…”

Section: A Squidsmentioning

confidence: 99%

Grain boundaries in high-Tcsuperconductors

2002

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Since the first days of high-T c superconductivity, the materials science and the physics of grain boundaries in superconducting compounds have developed into fascinating fields of research. Unique electronic properties, different from those of the grain boundaries in conventional metallic superconductors, have made grain boundaries formed by high-T c cuprates important tools for basic science. They are moreover a key issue for electronic and large-scale applications of high-T c superconductivity. The aim of this review is to give a summary of this broad and dynamic field. Starting with an introduction to grain boundaries and a discussion of the techniques established to prepare them individually and in a well-defined manner, the authors present their structure and transport properties. These provide the basis for a survey of the theoretical models developed to describe grain-boundary behavior. Following these discussions, the enormous impact of grain boundaries on fundamental studies is reviewed, as well as high-power and electronic device applications. CONTENTS I. Introduction 485 II. Introduction to Grain Boundaries 486 III. Preparation of Single Grain Boundaries 488 A. Bicrystalline junctions 489 B. Biepitaxial junctions 489 C. Step-edge junctions 491 IV. Structural Properties 491 V. Transport Properties of Grain Boundaries 496 A. Current-voltage characteristics 496 B. Critical current density 498 1. Dependence on grain-boundary angle 498 2. Temperature dependence of the critical currents 502 3. Magnetic-field dependence of the critical currents 502 C. Current-phase relation 504 D. Normal-state resistivity 504 E. The I c R n product 505 F. Grain-boundary capacitance 506 G. Microwave properties 507 H. Grain-boundary noise 507 I. Self-generated magnetic flux 509 J. Penetration of magnetic flux into grain boundaries 510 VI. Effects of Doping 510 VII. Grain-Boundary Mechanisms 511 A. Mechanisms based on structural properties 511 B. Mechanisms based on deviations from ideal stoichiometry 512 C. Order-parameter symmetry-based mechanisms 514 D. Interface charging and band bending 515 E. Mechanisms based on direct suppression of the pairing mechanism 516 VIII. Control of Grain Boundaries with Electric Fields or Quasiparticle Injection 517 A. Applied electric fields 517 B. Quasiparticle injection 518 IX. Irradiation of Grain Boundaries 518 A. Irradiation with electrons 518 B. Irradiation with light 518 C. Irradiation with ions 519 X. Bulk Applications 519 A. Powder-in-tube method 520 B. Coated conductors 520 XI. Applications of Grain Boundaries in Thin Films 522 A. SQUIDs 522 B. Radiation detectors and spectrometers 524 C. Three-terminal devices 525 D. Superconducting logic circuits 526 E. Research devices 526 XII. Summary and Outlook 528 Acknowledgments 529 References 529

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“…The details of our experiment have been reported elsewhere. [12][13][14][15] In addition, surface morphologies and profiles of these stepped substrates were observed using scanning electron microscopy ͑SEM͒ and atomic force microscopy ͑AFM͒.…”

Section: ͓S0003-6951͑00͒04010-9͔mentioning

confidence: 99%

Dynamic study and experimental “two-step process” of substrate step preparation for high-Tc Josephson junctions

Zhai

Zhang

Chu

et al. 2000

Applied Physics Letters

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We report theoretical and experimental studies of the dynamics of substrate step preparation for high-Tc Josephson junctions. A maximum step edge angle of 70.8° has been calculated for SrTiO3 (STO) substrates with a Nb mask. This calculated angle agrees well with our experimental result of 66°. Step-edge angles can be predicted for different purposes using this method. We also utilized a “two-step process” to improve the surface morphology of the stepped substrate, and step-edge Josephson junctions were fabricated with good uniformity.

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Four-channel YBa2Cu3O7−y dc SQUID magnetometer for biomagnetic measurements

Cited by 32 publications

References 8 publications

High-transition-temperature superconducting quantum interference devices

High-transition-temperature superconducting quantum interference devices

Grain boundaries in high-Tcsuperconductors

Dynamic study and experimental “two-step process” of substrate step preparation for high-Tc Josephson junctions

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