来源 Zotero
作者 Kaiwen Chen, Xiangqi Liu, Jiachen Jiao, Muyuan Zou, Chengyu Jiang, Xin Li, Yixuan Luo, Qiong Wu, Ningyuan Zhang, Yanfeng Guo, Lei Shu
arXiv / 出版方 https://link.aps.org/doi/10.1103/PhysRevLett.132.256503
PDF https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.132.256503
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发布日期 2024-06-21
研究范式 实验研究
样品形态 未知

摘要

The recently discovered superconductivity with critical temperature 𝑇𝑐 up to 80 K in the double-layer Nickelate La3⁢Ni2⁢O7−𝛿 under pressure has drawn great attention. Here, we report the positive muon spin relaxation (𝜇+⁢SR) study of polycrystalline La3⁢Ni2⁢O6.92 under ambient pressure. Zero-field 𝜇+⁢SR experiments reveal the existence of magnetic order in La3⁢Ni2⁢O6.92 with 𝑇𝑁=154 K. The weak transverse field 𝜇+⁢SR measurements reveal the bulk nature of magnetism. In addition, a small quantity of oxygen deficiencies can greatly broaden the internal magnetic field distribution sensed by muons.

材料

方法

  • Positive muon spin relaxation (μ+SR)
  • Weak transverse field μ+SR

关键词

亮点

  • Bulk nature of magnetism confirmed by weak transverse field μ+SR.

结论

  • Magnetic order exists in La3Ni2O6.92 with TN=154 K.
  • Oxygen deficiencies greatly broaden the internal magnetic field distribution.

主要论断

  • Bulk commensurate magnetic order (spin density wave) exists in La3Ni2O6.92 at ambient pressure with TN=154 K.
    • 证据: ZF-μSR spectra show oscillations below 148 K,wTF-μSR shows magnetic volume fraction reaches 90%,Fitting gives TN=154 K from Bfast1 temperature dependence (Eq.2)
  • Oxygen deficiencies broaden the internal magnetic field distribution sensed by muons.
    • 证据: Bfast2 component with large relaxation rate attributed to oxygen vacancies,Comparison of field distribution calculations with perfect crystal and vacancy model
  • The magnetic structure is consistent with a spin-charge stripe model with moments along c-axis, and the ordered moment is about 0.22-0.42 μB.
    • 证据: Dipole field calculation reproduces observed field strengths,Muon stopping site analysis

研究流程

  • Sample synthesis — High-quality polycrystalline sample with controlled oxygen deficiency.
    • 材料: La2O3 (99.999%); NiO (99.99%)
    • 方法: Solid-state reaction; Sintering at 1100°C in air for 50h, repeated 3 times
    • 观察: Powder X-ray diffraction confirms orthorhombic structure (space group Amam); TGA gives oxygen content La3Ni2O6.92
  • Physical property characterization — Bulk property measurements do not show clear anomaly at the magnetic transition due to oxygen inhomogeneity.
    • 材料: Polycrystalline pellet
    • 方法: Resistivity (four-probe method); Magnetization (SQUID)
    • 观察: Resistivity shows negative temperature coefficient, no anomaly near 150K; Magnetic susceptibility shows no magnetic phase transition down to 2 K, upturn at low T
  • Muon spin relaxation experiments — Evidence for bulk commensurate magnetic order with TN=154 K.
    • 材料: Polycrystalline La3Ni2O6.92 powder
    • 方法: Zero-field (ZF) and weak transverse field (wTF) μ+SR
    • 观察: ZF-μSR: Below 170 K, exponential decay; below 148 K, oscillations appear; Fourier transform shows multiple internal fields (10 mT, 140 mT, broad 160 mT); wTF-μSR: Oscillating signal decreases with cooling, reaching 90% magnetic volume fraction below 93K
  • Data analysis and interpretation — The magnetic order is commensurate SDW with possible stripe order; oxygen deficiencies significantly affect the internal field distribution.
    • 材料: μSR spectra
    • 方法: Least-squares fitting with Eq.(1) for ZF and Eq.(3) for wTF; MuFinder and CASTEP for muon stopping sites; DipoleCal for internal field calculation
    • 观察: Four magnetic components (three oscillating, one non-oscillating); Critical exponent β=0.26(2) suggests reduced dimensionality; Dipole field calculation consistent with spin-charge stripe model; Oxygen vacancies cause inhomogeneous broadening (Bfast2 component)