中国物理B ›› 2002, Vol. 11 ›› Issue (4): 379-382.doi: 10.1088/1009-1963/11/4/312

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Investigation the positive moments on the M－T curve of YBCO films measured by using zero-field cooling

王凤林1, 郭树权2, 高炬3, 周岳亮4, 赵柏儒4   

  1. (1)Applied Superconductivity Research Center, Department of Physics, Tsinghua University, Beijing 100084, China; (2)Applied Superconductivity Research Center, Department of Physics, Tsinghua University, Beijing 100084, China; National Laboratory for Superconductivity, Institute of Physics, Chinese Academy Science, Beijing 100080, China; Department of Physics, The Unive; (3)Department of Physics, The University of Hong Kong, Hong Kong, China; (4)National Laboratory for Superconductivity, Institute of Physics, Chinese Academy Science, Beijing 100080, China
  • 收稿日期:2001-04-20 修回日期:2001-12-13 出版日期:2002-04-13 发布日期:2005-06-13
  • 基金资助:
    Project supported by the National High Technology Development Programme of China (Grant No 863-CD090000).

Investigation the positive moments on the $M$$-$$T$ curve of YBCO films measured by using zero-field cooling

Guo Shu-Quan (郭树权)abc, Wang Feng-Lin (王凤林)a,   Zhou Yue-Liang (周岳亮)b, Zhao Bai-Ru (赵柏儒)b, Gao Ju (高炬)c   

  1. a Applied Superconductivity Research Center, Department of Physics, Tsinghua University, Beijing 100084, China; b  National Laboratory for Superconductivity, Institute of Physics, Chinese Academy Science, Beijing 100080, China; c Department of Physics, The University of Hong Kong, Hong Kong, China
  • Received:2001-04-20 Revised:2001-12-13 Online:2002-04-13 Published:2005-06-13
  • Supported by:
    Project supported by the National High Technology Development Programme of China (Grant No 863-CD090000).

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摘要： The superconducting transition of a YBCO film was measured by a MPMS-5 superconducting quantum interference device magnetometer, using a zero-field cooling process. The experimental results have shown that there are positive magnetic moment and positive peak on the M－T curve. We have proven that these anomalous behaviours are due to measurement error, but not phase transition. We have proposed a simple formula to explain and to calculate quantitatively these anomalous behaviours. It was found that, provided dH>0.59Hp (dH is the inhomogeneous field of the remnant field, Hp is the fully penetrated field of the measured sample), the experimental results will be positive, not negative. If dH≥2Hp, the experimental results will be symmetrical to their real negative values. From the M－T curve, which has positive moment and positive peak below Tc (superconducting transition temperature), we found a new possible method to obtain Hp of the measured sample.

Abstract: The superconducting transition of a YBCO film was measured by a MPMS-5 superconducting quantum interference device magnetometer, using a zero-field cooling process. The experimental results have shown that there are positive magnetic moment and positive peak on the $M$$-$$T$ curve. We have proven that these anomalous behaviours are due to measurement error, but not phase transition. We have proposed a simple formula to explain and to calculate quantitatively these anomalous behaviours. It was found that, provided dH>0.59Hp (dH is the inhomogeneous field of the remnant field, Hp is the fully penetrated field of the measured sample), the experimental results will be positive, not negative. If dH≥2Hp, the experimental results will be symmetrical to their real negative values. From the $M$$-$$T$ curve, which has positive moment and positive peak below Tc (superconducting transition temperature), we found a new possible method to obtain Hp of the measured sample.

Key words: SQUID magnetometer, remnant field, superconducting $M$$-$$T$ curve, flux pinning, positive moment, superconducting paramagnetic Meissner effect

中图分类号:  (Superconducting films and low-dimensional structures)

  • 74.78.-w
85.25.Dq (Superconducting quantum interference devices (SQUIDs)) 74.20.Mn (Nonconventional mechanisms) 74.25.Ha (Magnetic properties including vortex structures and related phenomena)