Threefold error in the reported zero-field cooled magnetic moment of single crystal La₂SmNi₂O₇

摘要

该论文指出，Li等人在高压镍酸盐超导体La₂SmNi₂O₇单晶的零场冷（ZFC）和场冷（FC）磁化测量中，对超导相分数的计算存在三重错误。首先，由于顺磁迈斯纳效应（Wohlleben效应），FC模式下样品的磁矩可能为正或负，因此不能用于计算超导相分数。其次，重新分析Li等人的ZFC数据后发现，按照其自身采用的计算方法，超导相分数应为22.8%，而非他们报告的62.1%，两者相差约三倍，主要源于退磁因子计算差异（Li等人取0.849，而作者使用Brandt公式算得0.81548）。第三，即使ZFC磁矩值计算正确，也无法直接用于确定超导相体积分数，因为存在无数种小于样品实际尺寸的超导区域形状和分布，均可产生相同的测量磁矩。作者强调，他们认同Li等人的实验证实了加压镍酸盐的体超导电性，但认为上述计算错误需要纠正，以免误导后续研究。

材料

• La₂SmNi₂O₇

方法

• demagnetization factor calculation
• magnetic moment analysis

关键词

• superconducting volume fraction
• demagnetization factor
• meissner effect

亮点

• Points out three specific errors in the volume fraction calculation by Li et al.
• Demonstrates that infinitely many smaller superconducting regions can produce the same measured moment.
• Calls for correction of published values to avoid misleading future research.

结论

• The reported superconducting volume fraction of 62.1% for La₂SmNi₂O₇ is a threefold overestimation.
• Correct calculation yields about 22.8%, due to differences in demagnetization factor and formula.
• FC data cannot be used for volume fraction calculation due to paramagnetic Meissner effect.
• The approach using ratio of measured to ideal Meissner moment is fundamentally ambiguous for volume fraction determination.

主要论断

• Li et al. made a threefold error in calculating superconducting volume fraction from ZFC data; correct ZFC fraction is 22.8% not 62.1%
  • 证据: From abstract: 'Li et al. made a threefold error in their calculations of the superconducting phase fraction in La₂SmNi₂O₇',Calculation yields 22.8% vs reported 62.1%
• FC data cannot be used for superconducting volume fraction calculations due to paramagnetic Meissner effect (Wohlleben effect)
  • 证据: From text: 'the FC data cannot be used for any superconducting phase fraction calculations, because of the paramagnetic Meissner effect'

研究流程

本批次暂无数据。