RESEARCH ON MAGNETIZATION AND ABNORMALY OF PIN-POTENTIAL IN HIGH-TEMPERATURE OXIDE SUPERCONDUCTORS

磁流蠕变的势垒高度随着温度T的增加而增加，而钉住势垒则随着温度T的增加而减小。Welch用非线性势垒U(J)定性地解释了这一异常，在高温度T时，分析中心围绕的电流J减小，因此非线性导致高温度T时钉住势垒能高。为了证实这一机制，需要一个大范围的J关系。将高温T_0 + DELTAT磁化的超导体冷却至工作温度T_0（高温磁化：HTM），可实现相当于长时间蠕变后的低磁化电流J态。HTM方法与附加在YBaCuO超导体上的冰雹电压测量相结合，得到了j范围内的磁弛豫曲线，并根据蠕变方程进行了仿真分析。利用HTM方法扩大了观测窗口，讨论了电流依赖性钉钉电位的性质。对磁流变进行了模拟，并与高温磁化后的磁松弛进行了比较。通过HTM.2后各蠕变曲线的平滑连接，得到了相当于几个月蠕变特征的偏置曲线。模拟的蠕变特性与HTM后的抑制蠕变曲线和偏置蠕变曲线进行了比较。由偏置蠕变曲线估计的潜在深度U_0表明，U_0随温度的降低而增大。

Barrier height for the flux creep increases with the temperature T, although the pinning potential is expected to decrease with increasing T.This anomaly was explained qualitatively by Welch by means of nonlinear potential barrier U(J) where the current J around which the analysis is centered decreases at high T and accordingly the nonlinearity leads to high pinning barrier energy at high T.To confirm this mechanism, U(J) relation of a wide range of J is required. By cooling a superconductor magnetized at higher temperature T_0 + DELTAT to an operating temperature T_0(High-Temperature Magnetization : HTM), low magnetization current J states equivalent to those after long-time creep are realized. The combination of the HTM method and the HaIl voltage measurement attached to YBaCuO superconductor gives the magnetic relaxation curve in a wide range of J.These creep curves are analyzed in details with the simulation based on the creep equation. The observation-window is enlarged by HTM method and the nature of the current dependent pinning potentials is discussed.Simulation of the flux creep is performed and compared with the magnetic relaxation after hightemperature magnetization.1. From short-time observations after HTM, offset creep curves equivalent to several months creep characteristics are obtained by smoothly connecting each creep curve after HTM.2. Simulated characteristics are favorably compared with both the suppressed creep curves after HTM and the offset creep curves.3. The potential depth U_0 estimated from the offset creep curves shows that U_0 increases as the temperature reduces.