高温超导体时效与记忆效应实验研究

熔融织构的钇钡铜氧化物(YBCO)高温超导块材具有较高的临界电流密度和较好的力学性能，在制作高场磁体、悬浮列车等方面具有重要的应用。本文首先在恒定的液氮温度下，通过对不同等待时间, 场冷和零场冷条件下悬浮力特征的测试, 发现高温超导块材在液氮温度表现出较强的时效性;接着，对于不同温度循环引起的悬浮系统悬浮力时间弛豫特征研究显示出高温超导块材在低温下具有鲜明的记忆特性，随着温度的升高，其记忆效应逐渐消失，且正、负温度循环对其记忆效应影响表现出不一致性。所有这些特性表明，高温超导块材具有和自旋玻璃类似的性质，其根源为超导体内部复杂的微观结构。

Experimental Investigation on Aging and Memory Effect of High-temperature Superconductor Bulks

Melt-textured yttrium barium copper oxide (YBCO) high-temperature superconductor (HTS) bulks has important applications in the production of high-field magnets, suspended train etc., due to its high critical current density and good mechanical properties. The levitation force measurement was carried out for YBCO HTS bulks at a constant temperature of liquid nitrogen and under different waiting times, field cooled and zero-field cooling conditions,respectively. It is found that HTS bulks presents rather strong aging effect and obvious memory characteristics at low temperatures. It is also found that waiting time has large effect on the zero-field-cooled (ZFC) and field-cooled (FC) levitation force, and the levitation force shows aging characteristic at the liquid nitrogen temperature. In Addition, the influence of negative and/or positive temperature cycles on the levitation force relaxation time was investigated in the case of zero field cooling (ZFC). Memory effect and its losing with temperature rising were found in experiment. Aging and memory properties presented here, are similar to spin-glass, which are caused by superconductor microstructures.