磁场扫描速度对测量高温超导体临界电流的影响

The Effect of Magnetic-Field Sweeping Rate on Measuring the Critical Current for Melt-Textured YBa_2Cu_3O_(7-δ) Crystals

实验中使用的样品是熔融织构Yba2Cu3O7-δ高温超导体,用振动样品磁强计(VSM)测量了样品在温度T=52 K和不同的磁场扫描速率(β=800,80,8,0.8,0.08 G/s)下的磁滞回线.通过运用Bean模型和电磁学理论对此数据的分析,得到ΔM~β曲线及E^jc曲线,发现有近似于幂指数规律,而且末端有向下倾斜的趋势,我们认为这是由于样品的钉扎和磁通蠕动机制发生了变化.结果表明磁滞回线测量的临界电流(jc)与磁场扫描速度β有关,所测临界电流随着磁场速度的减小而减小.

In experiments, the magnetic hysteresis loops of melt-textured Yba2Cu3O7-δ were measured by a vibrating sample magnetometer （VSM） at different magnetic-field sweep ratesβ（β=800, 80, 8, 0. 8, 0.08G/s respectively） and at a temperature of 52K. By using the Bean mode and the electric-magnetic theory, the ΔM-β curves and E-jc curves were obtained from these data. It is found that they exhibit power-law behaviors and little downward curvature at higher magnetic-field sweep rates. All the behaviors properly originate from the changing mechanism of flux pinning and flux creep. It is concluded that the critical current density jc is dependent on the magnetic-field sweep rate and the values are smaller at lowerβ.