Remagnetization of bulk high-temperature superconductors subjected to crossed and rotating magnetic fields
Remagnetization of bulk high-temperature superconductors subjected to crossed and rotating magnetic fields
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DOI：
10.1088/0953-2048/20/9/s10
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发表时间：
2007-09-01
影响因子：
3.6
通讯作者：
Campbell, A. M.
中科院分区：
文献类型：
--
作者：
Vanderbemden, P.;Hong, Z.;Campbell, A. M.
块体熔体加工的Y-Ba-Cu-O（YBCO）在各种高场永磁类应用中具有巨大的潜力，例如无刷电机的转子。然而，当用于这种旋转装置中时，YBCO可能受到不平行于磁化方向的瞬态和交变磁场的影响，并且对捕获场具有不利影响。这些效应可能导致大块样品的磁化强度长期衰减。在目前的工作中，我们分析了实验和数值模拟的再磁化过程中的熔融加工的YBCO单畴，已部分退磁的磁场垂直于初始方向的捕获磁通。磁转矩测量被用作一种工具，以探测在不同序列的外加磁场期间的剩磁变化。在平行于原始磁化方向的横向循环之间施加小磁场导致样品的部分再磁化。然而，旋转所施加的场被发现在重磁化散装材料时比施加相同幅度的磁化场脉冲有效得多。实验数据的主要特征可以使用基于E-J幂律的二维有限元数值模型定性地再现。最后，再磁化过程中示出的结果从复杂的修改的电流分布内的横截面的散装样品。
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.