Advances In Superconductivity Iv

Five years have passed since the breakthrough in the critical temperature for superconductors. During this period, many superconducting materials have been discovered and developed, and our knowledge of the physical and other properties of oxide superconductors has deepened through extensive and intensive research. This knowledge has advanced superconductivity science and technology from the initial questioning stage to a more developed but still uncertain second stage where research activity in superconductivity now overlaps with fields of application. Generally speaking, science resonates with technology. Science not only complements but also competes with or stimulates technology. New scientific knowledge has triggered the second technological research stage. Much progress has been made in the development of practical devices, encouraging the application of superconductors in areas such as human levitation, a high speed levitated bearing, large current transforming leads, and high frequency devices. This technological progress has increased our understanding of the science involved, such as flux pinning and dynamics, and anomalous long-range superconducting interactions. At this important stage, international cooperation and collaborative projects can effectively sustain aggressive research and development in order to advance superconductivity to the next stages. The ISS Symposium is expected to serve as a venue for increasing our knowledge of superconductivity and for exchanging visions for future research and applications, through the presentation and discus of the latest research results. These proceedings also aim to summarize sion annual progress in high-Tc superconductivity in all fields.

This book covers all research fields in high Tc Superconductivity. Breakthrougs in the single crystal growth of a monolithic device leads to a new technology.

More than seven years have passed since the dramatic breakthrough in the critical temperature for superconductors. During this period, a host of new materials have been discovered, and efforts have been stepped up in a variety of domains including device and systems applications, commercialization, and basic research on the properties of superconductive materials. Recent progress in areas such as bulk single crystal production, long-scale wire and tape produc tion, flywheel and bearing applications, and electronic device applications for thin films indicate that science and technology have been working hand in hand in this field, as has been the case in the research and development of semi conductors. This interdisciplinary "resonance" will be certain to lead to further outstanding advances in the years to come. It goes without saying that worldwide information exchange is the key to accelerating progress in superconductivity science and technology. As in previous years, the ISS '93 served as a venue where visions of future develop ments were shared in addition to presentations and extensive discussions on the most up-to-date research results. I hope that the Proceedings contained in this volume will be consulted not only as a summary of the current "state of the art" in high-Tc superconductivity but also as a stimulating source of ideas regarding future applications of superconductivity research.

The field of high-temperature superconductivity has encouraged an inter disciplinary approach to research. It has required significant cooperation and collaboration among researchers, each of whom has brought to it a rich variety of experience from many other fields. Recently, great improvements have been made in the quality of research. The subject has matured and been launched into the next stage through the resonance between science and technology. The current progress of materials processing and engineering in this field is analogous to that previously seen in the development of semiconductors. These include the appearance of materials taking the place of YBa2Cu307 owing to their improved properties (higher critical temperatures and stronger flux pin ning) in which rare earth ions with large radii (La, Nd, Sm) substitute for Y; the development of technology enabling growth control on the nanometer scale; and precise and reproducible measurements that can be used as rigorous tests of theoretical models, which in turn are expected to lead to the develop ment of new devices. For further progress in high-T research, academics and c technologists must pool their knowledge and experience. I hope that this volume will promote that goal by providing the reader with the latest results of high-temperature superconductor research and will stimulate further discussion and collaboration.

The International Symposium on Superconductivity, which has been held annu ally since 1988, is a forum for presenting the most up-to-date information about a broad range of research and development in superconductivity, from funda mental aspects to applications. More than 10 years have passed since the discovery of oxide superconductors and since various developments of applications began. It may be said that the prospects for application of oxide superconductors recently have opened up. Great progress has been made toward practical use, for example, of the flywheel, which uses bulk materials, and the high-performance cryo-cooled magnet made of bismuth wire. These were the results of persistent efforts to develop materials from the viewpoint of materials science and engineering. Also important is the progress in comprehensive understanding of high temperature superconductivity. Unique electronic properties of cuprates such as the non-Fermi liquid normal state, spin-charge separation, spin gap, and d-wave symmetry were discussed at the symposium, as were the unique electromagnetic properties resulting from the low dimensionality of cuprates. In the field of new superconductors, many exotic materials have been discovered since 1986. A decade of work with cuprate superconductors is reviewed in this proceedings, and several of the newest materials are presented. These papers will be instructive for many researchers and for students who are to enter this field.

Five years have passed since the breakthrough in the critical temperature for superconductors. During this period, many superconducting materials have been discovered and developed, and our knowledge of the physical and other properties of oxide superconductors has deepened through extensive and intensive research. This knowledge has advanced superconductivity science and technology from the initial questioning stage to a more developed but still uncertain second stage where research activity in superconductivity now overlaps with fields of application. Generally speaking, science resonates with technology. Science not only complements but also competes with or stimulates technology. New scientific knowledge has triggered the second technological research stage. Much progress has been made in the development of practical devices, encouraging the application of superconductors in areas such as human levitation, a high speed levitated bearing, large current transforming leads, and high frequency devices. This technological progress has increased our understanding of the science involved, such as flux pinning and dynamics, and anomalous long-range superconducting interactions. At this important stage, international cooperation and collaborative projects can effectively sustain aggressive research and development in order to advance superconductivity to the next stages. The ISS Symposium is expected to serve as a venue for increasing our knowledge of superconductivity and for exchanging visions for future research and applications, through the presentation and discus of the latest research results. These proceedings also aim to summarize sion annual progress in high-Tc superconductivity in all fields.

Provides coverage of the ongoing investigations on bismuth-based high-temperature cuprate superconductors, integrating scattered research activities and literature from 70 leading scientists throughout the world. The text covers crystal structures and microstructures, reversible or equilibrium magnetic and thermal properties, atomic site tunnel spectroscopy, experimental studies concerning equilibrium phases, and more.

Since the discovery of superconductivity with trans1tton temperatures above 77 K, concentrated research activities toward the exploration of practical applica tions of these materials have been carried out. Currently, a remarkable improve ment in superconducting properties has been achieved due to the fine optimization of fabrication processes, and this has attracted industrial interest for future applications. In the case of NdBa Cu 0 materials, a new pinning mecha 2 3 7 nism was found which enhances the critical current under applied magnetic fields. In single crystals of these materials, oxygen control results in an increase in the growth rate. The metalorganic chemical vapor deposition (MOCVD) film quality has been improved by using a new liquid raw material. Simultaneously, real demands from the viewpoint of the market start to be a motivation force, es pecially in electronics application where some products are already being sold. At the same time, interesting physical properlies have been obtained from a new superconducting single crystal which has a layered perovskite structure without copper. In addition, various precision measurement techniques have confirmed the d-wave mechanism and the existence of intrinsicJosephson junctions in single crystals. These new phenomena challenge the existing theoretical models but also open the way for new applications. These significant areas of progress in materials science have led high-Tc super conductivity research into the next phase of activity, while fundamental research continues to be very important. I sincerely hope that this volume will give further impetus to this development.