弱场下熔融织构YBa_2Cu_3O_(7-δ)样品局域磁通蠕动的实验研究

EXPERIMENTAL STUDY OF LOCAL FLUX CREEP ON A CYLINDRICAL MELTING-TEXTURED GROWN YBa_2Cu_3O_(7-δ) SAMPLE AT APPLIED FIELDS

利用半导体霍尔探头测量法在液氮温度下研究了低场下圆柱状熔融织构YBa2 Cu3O7-δ样品的局域磁通蠕动行为 .对瞬时加减场样品端面局域磁场的磁弛豫 ,磁滞回线以及不同扫场速率下局域磁场的变化进行了测量 ,观察到了对数时间磁弛豫的行为 ,发现由加场和去场数据所得的激活能U0 有明显的不同 .磁滞回线测量中 ,局域点的磁场随外场几乎同步变化 ,不同扫场速率下局域磁场随外场变化的差别不大 .实验结果表明 ,外场除对样品侧面外 ,对端面也有明显的穿透 .所得U0 的不同来源于磁通线与ab平面的位置关系 .

Using semiconductor Hall probes,we studied the local flux creep on a cylindrical melting\|textured grown YBa\-2Cu\-3O 7-δ sample at liquid nitrogen temperature and low applied field.The measurements on the top surface of the sample show that the local flux creep fits well the logarithmic time dependence in both the field\|on and field\|off cases.The obtained activation energy U\-0 in the field\|on case is greater than the field\|off one.The local magnetization was almost changing with the applied field synchronously in the measurement of magnetic hysteresis loops.The field was almost identical at a fixed local point under various sweep ratios of the applied field.The results imply that besides the side surface the applied field penetrates into the upper and lower surfaces to a certain extent too.The disparity in U\-0 results from the difference of the angle between the flux line and the ab plane.This study also shows that the measurement of flux creep at the low field has a potential to become a simple and effective method to investigate the pinning property in large size samples.