Elastic and plastic behavior of a fluxoid lattice in the saturation region of the global pinning force in superconducting Nb-Ta.
Elastic and plastic behavior of a fluxoid lattice in the saturation region of the global pinning force in superconducting Nb-Ta.
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超导 Nb-Ta 中全局钉扎力饱和区域中通量晶格的弹性和塑性行为。
DOI：
10.1103/physrevb.33.3134
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Miyamoto
中科院分区：
文献类型：
--
作者：
Matsushita;Itoh;Kikitsu;Miyamoto
我们使用交流技术研究了全局钉扎力密度饱和区域中磁通晶格的弹性和塑性行为。样品为 Nb-50-at。 ％Ta变形不同量。从力-距离分布中获得的弹性模量..cap alpha..随着钉扎强度的增加而增加，并随着磁场的增加而逐渐减少。在上临界场附近的饱和区域和下临界场的非饱和区域之间没有观察到 ..cap α 的显着变化。这表明，即使在克拉默模型中假设的饱和区域，钉扎力也会阻止通量体流动，但通量晶格的剪切力不会阻止通量体流动。另一方面，相互作用距离 d/sub i/，即磁通脱钉所需的位移，在两个区域之间发生巨大变化：它随着饱和区域中的磁场而突然减小。该区域中的 d/sub i/ 值随着钉扎强度的增加而降低。 d/sub i/ 的突然降低表明磁通体晶格随着磁场的增加而变得更加脆弱，并且整个磁通体晶格的灾难性流动引发了向电阻状态的转变。在本文中，作者更多 » 提出饱和区中灾难性的全局磁通流是由磁通晶格局部塑性变形的发生引起的。预计在施加驱动力之前已经存在的通量晶格缺陷周围会引起局部塑性变形。在此模型中，假设发生塑性变形的概率与通量晶格缺陷的浓度成正比。« less
We investigate the elastic and plastic behavior of the fluxoid lattice in the saturation region of the global pinning-force density using the ac technique. The specimens were Nb-50-at. % Ta deformed by various amounts. The elastic modulus ..cap alpha.. obtained from the force-distance profile increased with the pinning strength and decreased gradually with increasing magnetic field. No remarkable change in ..cap alpha.. was observed between the saturation region near the upper critical field and the nonsaturation one at lower fields. This reveals that fluxoids were prevented from flowing by the pinning forces but not by the shear force of the fluxoid lattice even in the saturation region as assumed in Kramer's model. On the other hand, the interaction distance d/sub i/, the displacement necessary for fluxoids to be depinned, changed drastically between the two regions: It decreased abruptly with the magnetic field in the saturation region. Values of d/sub i/ in this region decreased with the pinning strength. The abrupt decrease of d/sub i/ indicates that the fluxoid lattice becomes more fragile with increasing magnetic field and that a transition to the resistive state is initiated by a catastrophic flow of the whole fluxoid lattice. In this paper the authorsmore » propose that the catastrophic global flux flow in the saturation region is caused by the occurrence of a local plastic deformation of the fluxoid lattice. Local plastic deformations are expected to be induced around defects of the fluxoid lattice which already exist before an application of the driving force. In this model, the probability of occurrence of a plastic deformation is assumed to be proportional to the concentration of fluxoid-lattice defects.« less