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arXiv:2308.03110cond-mat.supr-con

Ferromagnetic half levitation of LK-99-like synthetic samples

Kaizhen Guo, Yuan Li, Shuang Jia

Abstract

We successfully synthesized polycrystalline LK-99-like ceramic samples with a solid-state-sintering method. Powder X-ray diffraction shows that the main contents are $\mathrm{Pb_{10-x}Cu_x(PO_4)_6O}$ and $\mathrm{Cu_2S}$, consistent with recent reports [arXiv:2307.12037; arXiv:2308.01192]. In some small flaky fragments, we successfully observed ``half levitation'' atop a $\mathrm{Nd_2Fe_{14}B}$ magnet. Using magnetization measurements on such small pieces, as well as on a large piece which does not exhibit the half levitation, we show that the samples ubiquitously contain weak yet definitive soft ferromagnetic components. We argue that, together with the pronounced shape anisotropy of the small fragments, the soft ferromagnetism is sufficient to explain the observed half levitation in strong vertical magnetic fields. Our measurements do not indicate the presence of the Meissner effect, nor zero resistance, in our samples, leading us to believe that our samples do not exhibit superconductivity. The precise chemical composition and the physics behind the ferromagnetic component remain outstanding questions to be addressed in future research.

arXiv comments
10 pages, 10 figures
Journal reference
SCIENCE CHINA Physics, Mechanics & Astronomy , Volume 66, Issue 10: 107411 (2023)
DOI
doi:10.1007/s11433-023-2201-9
Subjects
cond-mat.supr-conSuperconductivity cond-mat.str-elStrongly Correlated Electrons

On Hacker News

Linked by 7 identifiable commenters in 11 comments across 7 threads, from Aug 2023 to Aug 2023. Found in 1 HN submission from Aug 2023 to Aug 2023. Open submission discussions.

Comments linking this paper, per year.

Discussed in comments7 threads

  1. LK-99 isn’t a superconductor 1 comment

    • Copper sulfide's diamagnetism is not that high. It would be notable if it were. So that isn't a possible explanation. Cu2S was suggested as a culprit for the observed conductivity changes. The preprint reporting the high value of diamagnetism is here…

      scytheView on HNParent context

  2. Indian lab observes LK-99 sample standing vertically in magnetic field 1 comment
  3. Flux Pinning in sample of LK-99? 1 comment
  4. Beijing Superconductor Levitation Video Author Admits Fraud, Takes It Down 1 comment

    • The preprint from earlier showing that LK99 is not superconductive and the 'half-levitating' samples have regions of soft-ferromagnetism and diamagnetism and shows a semiconductive temperature-resistance curve: https://arxiv.org/abs/2308.03110 Discussion on the preprint from…

      lamontcgView on HNParent context

  5. LK-99 is an online sensation but replication efforts fall short 1 comment

    • Well it looks like I'm right and LK99 is ferromagnetic and not superconductive. And the paper that shows it looks a lot more like I'd expect good science to look: https://arxiv.org/abs/2308.03110 Difference between science and spectacle.

      lamontcgView on HNParent context

  6. We now believe that the game is over. LK-99 is not a superconductor 5 comments

    • https://arxiv.org/abs/2308.03110

      bigbacaloaView on HNParent context

    • This study https://arxiv.org/abs/2308.03110

      nisegamiView on HNParent context

    • > I feel like such strong statements should directly reference strong evidence. They did link the strong evidence upthread: https://arxiv.org/abs/2308.03110 > To conclude, we have observed a semiconductor-like, non-superconducting electric property in our LK-99-like synthetic…

      lamontcgView on HNParent context

    • They're citing a study from the International Center for Quantum Materials at Peking University in Beijing (which has several Alumni from the Condensed Matter Theory Center at U of Maryland which is the twitter account) which goes into the matter in some depth and finds that…

      lamontcgView on HNParent context

    • What really annoys me is that we have not seen a single reproduction of LK-99 yet. A lot of the arxiv papers will measure PXRD. Then they will say stuff like "the position of the peaks is almost identical" (https://arxiv.org/pdf/2308.03110.pdf) (emphasis is mine). Anyone who…

      awwkawView on HNParent context

  7. Absence of superconductivity in LK-99 at ambient conditions 1 comment

    • This isn't a particularly meaningful paper because they failed to produce any kind of partial levitation. This one which finds substantial ferromagnetism and minimal diamagnetism is a far better reason to doubt that LK-99 is a superconductor: https://arxiv.org/abs/2308.03110…

      TillEView on HNParent context

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