Gd-Ba-Cu-O立方块体超导体的交叉场退磁：测量和三维模拟
Demagnetization of cubic Gd-Ba-Cu-O bulk superconductor by cross-fields: measurements and 3D modelling
摘要：
超导块材，作为高场永磁体，在许多应用中是有希望的。块体永磁体中的一个重要效应是交叉场退磁，由于相对较小的横向场，交叉场退磁可以减小超导体中的磁场。正交场退磁还没有研究过样品形状，如矩形棱柱或立方体。这一贡献提出了一个研究的基础上，三维数值模拟和实验。我们研究了一个立方Gd-Ba-Cu-O块状超导体样品的尺寸为6 mm的磁化场冷却在一个外部磁场约1.3 T，这是后来提交到交叉场磁场高达164 mT。除横向场为初始俘获场的50%或以上外，模拟结果与实验结果一致。当前路径呈现出强烈的3D性质。例如，在垂直于初始磁化场的中平面处，该方向上的电流密度从横向侧处的临界量值${J_c}$平滑地变化到某一穿透深度处的零。这表明电流密度随幅度${J_c}$旋转，因此预计像磁通切割这样的无力效应将发挥重要作用。
英文摘要：
Superconducting bulks, acting as high-field permanent magnets, are promising for many applications. An important effect in bulk permanent magnets is crossed-field demagnetization, which can reduce the magnetic field in superconductors due to relatively small transverse fields. Crossed-field demagnetization has not been studied in sample shapes such as rectangular prisms or cubes. This contribution presents a study based on both 3D numerical modelling and experiments. We study a cubic Gd-Ba-Cu-O bulk superconductor sample of size 6 mm magnetized by field cooling in an external field of around 1.3 T, which is later submitted to crossed-field magnetic fields of up to 164 mT. Modelling results agree with experiments, except at transverse fields 50\% or above of the initial trapped field. The current paths present a strong 3D nature. For instance, at the mid-plane perpendicular to the initial magnetizing field, the current density in this direction changes smoothly from the critical magnitude, ${J_c}$, at the lateral sides to zero at a certain penetration depth. This indicates a rotation of the current density with magnitude ${J_c}$, and hence force free effects like flux cutting are expected to play a significant role.
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