Study of high current density superconducting conductor introduced by microfabrication technique.

用于电力电缆和高场磁体的实用超导导线需要高临界电流密度。为了获得高的临界电流密度，这些实用超导体的发展需要有效的磁通钉扎中心。在金属超导体的情况下，拉伸过程在金属超导体中引入了人造钉扎中心。然而，人工钉扎中心不能通过拉伸工艺引入高温超导体，因为这些超导体是脆性的。为了在超导体中引入人工钉扎中心，我们考虑采用微加工技术，而不是拉伸工艺。采用光刻技术在0.2 2~0.5μm厚的氧化镁或蓝宝石衬底上蒸发Nb薄膜中引入槽状和孔状人工钉扎中心。在Nb薄膜0.9×0.9 mm的区域上刻蚀得到了2μm和4μm两种间距的槽状图形。制备了不同沟槽深度的Nb薄膜，研究了沟槽深度对磁矩磁滞曲线宽度的影响。用SQUID磁强计测量了开槽试件的磁滞回线。对于超过70%的薄膜厚度，磁滞曲线的宽度随着凹槽深度的增加而减小。

Practical superconducting wires for power cables and high field magnets require a high critical current density. Effective flux pinning centers are required for the development of these practical superconductors in order to achieve high critical current density. In the case of metallic superconductors, a drawing process introduces artificial pinning centers in metallic superconductors. However, artificial pinning centers cannot be introduced into high-Tc superconductors through the drawing process because these superconductors are brittle. We consider the microfabrication technique, instead of the drawing process, in order to introduce artificial pinning centers into the superconductors. Groove-shaped artificial pinning centers and hole-shaped artificial pinning centers are introduced into 0.22-0.5μm thick evaporated Nb film on a MgO substrate or a sapphire substrate by photolithography. The groove-shaped patterns with two kind of spacing of 2μm and 4μm were introduced by etching on a 0.9 × 0.9mm region of the Nb film. Nb films with varying groove depths were prepared, and the groove depth dependence on critical current density was investigated for the width of the hysteresis curve of the magnetic moment. The hysteresis curves of the specimens with grooves were measured with a SQUID magnetometer. The width of the hysteresis curve decreases with an increasing groove depth for over 70% of the film thickness.