Collapse of the magnetization by the application of crossed magnetic fields: observations in a commercial Bi:2223/Ag tape and comparison with numerical computations
Collapse of the magnetization by the application of crossed magnetic fields: observations in a commercial Bi:2223/Ag tape and comparison with numerical computations
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DOI：
10.1088/0953-2048/28/2/025012
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发表时间：
2015-02-01
影响因子：
3.6
通讯作者：
Lacroix, C.
中科院分区：
文献类型：
--
作者：
Celebi, S.;Sirois, F.;Lacroix, C.
本文报道了交叉磁场对商用Bi：2223/Ag超导带材的影响。通过施加或改变外部磁场在样品中产生的大磁矩当随后施加磁场时，垂直于带材平面，因此沿着微晶的c轴的磁场（表示为H-z）的幅值显著减小（表示为H-y）沿着带的平面，因此沿着微晶的ab平面，被压印和去除，并使其在相反方向上经历几个半周期的振荡。我们发现，几个周期导致的磁矩迅速离开临界状态的主要磁滞包络线，并达到渐近可逆的抗磁迈斯纳矩M-rev，这是在磁带的平面外方向（c轴）对齐。我们观察到，交叉领域的应用程序，首先沿着的c轴，然后沿着的ab平面，有效地抑制了体钉扎磁矩，并淬火相关的持续电流在ab平面中流通。我们的数值计算，基于有限元方法和使用E-J幂律模型的超导体，可以再现定性的实验数据。在数值模型中，电流密度垂直于磁场的两个分量变化的平面流动。这些调查表明，所观察到的磁化衰减的结果从复杂的修改的电流分布由于在样品横截面内的交叉磁场的应用。
We report on the effects of crossed magnetic fields on a commercial Bi:2223/Ag tape superconductor. The large magnetic moments which are generated in the specimen by the application or change of an external magnetic field (denoted H-z) directed perpendicularly to the plane of the tapes, hence along the c-axis of the crystallites, are considerably reduced in magnitude when subsequently a magnetic field (denoted H-y) directed along the plane of the tape, hence along the ab plane of the crystallites, is impressed and removed and made to undergo several half cycles of oscillations in the opposite direction. We find that a few cycles cause the magnetic moment to rapidly depart from the critical state major hysteresis envelope and reach asymptotically the reversible diamagnetic Meissner moment M-rev, which is aligned in the out-of-plane direction of the tape (c-axis). We observe that the application of crossed fields, first along the c-axis, then along the ab plane, effectively suppresses the bulk pinning magnetic moment, and quenches the associated persistent currents circulating in the ab plane. Our numerical computations, based on the finite element method and using an E-J power law to model the superconductor, can reproduce qualitatively the experimental data. In the numerical model, the current density flows perpendicularly to the plane within which the two components of the magnetic field vary. These investigations show that the observed decay in magnetization results from the complicated modification of current distribution due to the application of crossed magnetic fields within the sample cross section.