Vortex Pinning in Thin Film Superconductors by Controlled Pinning Structures

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w:\awards\awards96\*.doc 9801921 Schuller This experimental research project is concerned with vortex pinning in thin film superconductors by controlled pinning structures. It is a joint experimental/theoretical study of the physics of vortices in low and high Tc thin films subject to artificial pinning. The pinning structure is engineered using state-or-the-art lithography processes. Pinning structures under study include regular and weakly disordered arrays of "holes", and/or "stripes" made of normal or magnetic materials. The pinning characteristics of these arrays over a wide range of temperature, field and materials parameters will be characterized by transport, noise, and direct imaging measurements. Novel pinning patterns will be used to expand the pinned phase to a broad range of magnetic fields, beyond the nominal matching field, to enhance vortex pinning. They also provide new "media" in which a variety of new and interesting vortex phenomena can be studied. Theory is an inherent part of the project. New fabrication methods and devices will be developed using state of the art thin film techniques together with forefront lithography processes. This research program is interdisciplinary in nature and involves several pre- and post-graduate researchers in its activities. They will become familiar with research equipment and methods applicable to condensed matter physics, microelectronics, magnetic recording and sensors, and superconducitng devices. Their training will be excellent preparation for careers in industry, government laboratories or academia. %%% This experimental basic research project is concerned with increasing the current carrying capacity of superconducting thin films. The "critical" current of a superconductor in the presence of a magnetic field is influenced by "pinning centers" which act as anchors fo r the magnetic flux lines (vortices) which penetrate the thin film. The critical current can be increased by increasing the pinning. This study investigates vortex pinning in thin film superconductors by controlled pinning structures. It is a joint experimental/theoretical study of the physics of vortices in low and high Tc thin films subject to artificial pinning. The pinning structure is engineered using state-or-the-art lithography processes. Pinning structures under study include regular and weakly disordered arrays of "holes", and/or "stripes" made of normal or magnetic materials. The pinning characteristics of these arrays over a wide range of temperature, field and materials parameters will be characterized by transport, noise, and direct imaging measurements. Novel pinning patterns will be used to expand the pinned phase to a broad range of magnetic fields, beyond the nominal matching field, to enhance vortex pinning. They also provide new "media" in which a variety of new and interesting vortex phenomena can be studied. Theory is an inherent part of the project. New fabrication methods and devices will be developed using state of the art thin film techniques together with forefront lithography processes. This research program is interdisciplinary in nature and involves several pre- and post-graduate researchers in its activities. They will become familiar with research equipment and methods applicable to condensed matter physics, microelectronics, magnetic recording and sensors, and superconducitng devices. Their training will be excellent preparation for careers in industry, government laboratories or academia. ***