Suppressed density wave and emergent negative magnetoresistance in Tb-doped La₃Ni₂O₇

Summary

The suppression of density wave in bilayer nickelate La₃⁢Ni₂⁢O₇ under pressure has been identified as a critical factor enabling pressure-induced high-temperature superconductivity. However, this density wave state exhibits remarkable stability against most alternative tuning methods except the high-pressure technique. Herein through systematic investigations of Tb doping effects on electrical transport and magnetic properties, we observe a gradual suppression of density wave transition temperature with the increasing Tb concentration, accompanied by the emergence of negative magnetoresistance persisting up to 14 T. Magnetic susceptibility measurements further reveal the formation of a doping-induced spin-glass state, which likely accounts for the observed negative magnetoresistance phenomenon. This work establishes an effective chemical doping approach to manipulate the density wave state and correlated quantum state in La₃⁢Ni₂⁢O₇, offering new insights into the mechanism of high-temperature superconductivity and potential pathways toward achieving ambient-pressure superconductivity in bulk nickelate crystals.

Materials

• Tb-doped La₃Ni₂O₇

Methods

• Electrical transport measurements
• Magnetic susceptibility measurements

Keywords

• density wave
• negative magnetoresistance
• spin glass state

Highlights

• This work establishes an effective chemical doping approach to manipulate the density wave state in La₃Ni₂O₇.

Conclusions

• Tb doping suppresses the density wave transition and induces negative magnetoresistance, likely due to the formation of a spin-glass state.

Main claims

• Tb doping gradually suppresses the density wave transition temperature in La₃Ni₂O₇.
  • Evidence: Abstract: 'we observe a gradual suppression of density wave transition temperature with the increasing Tb concentration',Full text: 'Both the valley and peak positions shift to lower temperature, suggesting a doping-induced suppression effect of density wave' (referring to dρ/dT features),Full text: 'the collective downward shift of all characteristic temperatures (Tpeak, Tvalley, and T*) upon Tb doping provides compelling evidence for the gradual suppression of density wave correlations.'
• Tb doping induces a spin-glass state and negative magnetoresistance in La₃Ni₂O₇.
  • Evidence: Abstract: 'emergence of negative magnetoresistance persisting up to 14 T. Magnetic susceptibility measurements further reveal the formation of a doping-induced spin-glass state',Full text: 'a broad peak near 4.5 K is observed in the real part of La₂.7Tb₀.3Ni₂O₇ sample and the peak slightly shifts to higher temperature as the frequency increases, consistent with the typical feature in a spin-glass system',Full text: 'the negative magnetoresistance suddenly turns negative at 2, 10, 20, and 30 K under the field up to 14 T.'

Workflow

• sample_synthesis_and_chemical_characterization — Tb doping successfully replaces La while maintaining bilayer structure and inducing chemical pressure.
  • Materials: La_3-xTb_xNi₂O₇ (x=0, 0.1, 0.2, 0.3); Precursors for sol-gel method
  • Methods: Sol-gel synthesis; Powder X-ray diffraction (Rigaku SmartLab, Cu Kα1); EDX (Zeiss cross beam 550L, JEOL F₂₀₀); XPS (Escalab 250 Xi, Al Kα)
  • Observations: Single-phase Amam structure for all x; Lattice constants contract with Tb doping; Ni valence ~+2.5, uniform Tb distribution
• electrical_transport_and_magnetic_measurements — Tb doping suppresses the density wave transition and induces a spin-glass state, causing negative magnetoresistance.
  • Materials: Polycrystalline bars; Silver paste contacts
  • Methods: Four-probe resistivity (PPMS DynaCool); Magnetoresistance up to 14T; Magnetic susceptibility (MPMS₃, DC and AC); Curie-Weiss fitting
  • Observations: Density wave anomaly (peak/valley in dρ/dT) shifts to lower temperature with doping; Weak localization at low T (ρ ≈ ln T); Negative MR up to -3.4% at 2 K in doped samples; Spin-glass behavior below ≈5 K (frequency-dependent peak in χ'); Ferromagnetic-like hysteresis at 2K