Spin-charge-orbital order in nickelate superconductors

Summary

Spin-charge-orbital order in nickelate superconductors

Materials

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Methods

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Keywords

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Highlights

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Conclusions

Not available in this batch.

Main claims

• The magnetic ground state of La₃Ni₂O₇ is a double spin stripe (DS₁) order, characterized by ferromagnetic nearest-neighbor and antiferromagnetic second-neighbor in-plane interactions, and strong interlayer antiferromagnetic coupling.
  • Evidence: DFT+U calculations show DS₁ lowest among all 2×2×1 configurations,Fitted exchange: J₁=-1.1 meV, J₂=6.5 meV, J⊥≈124 meV
• Interlayer magnetic exchange is much larger than intralayer exchange in La₃Ni₂O₇.
  • Evidence: J⊥ values (≈124 meV) are two orders of magnitude larger than J₁/J₂

Workflow

• dft_calculations_of_magnetic_configurations — DS₁ is the magnetic ground state.
  • Materials: La₃Ni₂O₇ and La₄Ni₃O₁₀ crystal structures
  • Methods: DFT+U calculations using VASP; All possible magnetic configurations in 2×2×1 supercells
  • Observations: DS₁ (double spin stripe) is lowest in energy for La₃Ni₂O₇; Outer layers of La₄Ni₃O₁₀ prefer DS₁, inner layer shows different order
• fitting_of_magnetic_exchange_interactions — Interlayer exchange is much stronger than intralayer; DS₁ is stabilized by the combination of FM J₁ and AFM J₂.
  • Materials: Energies of ≈80 non-equivalent magnetic configurations
  • Methods: Machine learning fitting of Heisenberg Hamiltonian; Landau expansion for moment dependence
  • Observations: J₁ ≈ -1.1 meV (FM), J₂ ≈ 6.5 meV (AFM), J⊥ ≈ 124 meV (AFM) for U=1 eV; Splitting of exchange paths
• strain_effect_simulation — Strain can alter magnetic ordering.
  • Materials: La₃Ni₂O₇ under compressive strain
  • Methods: DFT with fixed c and relaxed a,b
  • Observations: Zigzag magnetic order becomes ground state under compressive strain