superconductivity; magnetic measurements; crossed fields
Abstract :
[en] Bulk melt-processed Y-Ba-Cu-O (YBCO) has significant potential for a variety of high-field permanent-magnet-like applications, such as the rotor of a brushless motor. When used in rotating devices of this kind, however, the YBCO can be subjected to both transient and alternating magnetic fields that are not parallel to the direction of magnetization and which have a detrimental effect on the trapped field. These effects may lead to long-term decay of the magnetization of the bulk sample. In the present work, we analyze both experimentally and numerically the remagnetization process of a melt-processed YBCO single domain that has been partially demagnetized by a magnetic field applied orthogonal to the initial direction of trapped flux. Magnetic torque measurements are used as a tool to probe changes in the remanent magnetization during various sequences of applied field. The application of a small magnetic field between the transverse cycles parallel to the direction of original magnetization results in partial remagnetization of the sample. Rotating the applied field, however, is found to be much more efficient at remagnetizing the bulk material than applying a magnetizing field pulse of the same amplitude. The principal features of the experimental data can be reproduced qualitatively using a two-dimensional finite-element numerical model based on an E-J power law. Finally, the remagnetization process is shown to result from the complex modification of current distribution within the cross-section of the bulk sample.
Research Center/Unit :
SUPRATECS - Services Universitaires pour la Recherche et les Applications Technologiques de Matériaux Électro-Céramiques, Composites, Supraconducteurs - ULiège
Disciplines :
Electrical & electronics engineering Physics
Author, co-author :
Vanderbemden, Philippe ; Université de Liège - ULiège > Capteurs et systèmes de mesures électriques
Hong, Z.; University of Cambridge > Centre for Advanced Photonics & Electronics (CAPE)
Coombs, T. A.; University of Cambridge > Centre for Advanced Photonics & Electronics (CAPE)
Ausloos, Marcel ; Université de Liège - ULiège > Département de physique > Physique statistique appliquée et des matériaux
Babu, N. H.; University of Cambridge > IRC in Superconductivity
Cardwell, D. A.; University of Cambridge > IRC in Superconductivity
Campbell, A. M.; University of Cambridge > IRC in Superconductivity
Language :
English
Title :
Remagnetization of bulk high-temperature superconductors subjected to crossed and rotating magnetic fields
Publication date :
September 2007
Event name :
Campbell Conference on Flux Pinning and Related Effects