Quantum magnetisms in uniform triangular lattices Li₂AMo₃O₈ (A = In, Sc)

Area of Science:

• Condensed Matter Physics
• Materials Science
• Magnetism

Background:

• Molecular-based spin-1/2 triangular lattice systems, like LiZn₂Mo₃O₈, are of interest due to geometrical frustration leading to exotic ground states.
• Li₂AMo₃O₈ (A = In, Sc) compounds feature uniform triangular lattices of spin-1/2 Mo₃O₁₃ clusters, with differing ground states based on the A-site element.
• Li₂InMo₃O₈ orders magnetically at 12 K, whereas isomorphic Li₂ScMo₃O₈ shows no long-range order down to 0.5 K.

Purpose of the Study:

• To investigate the exotic magnetic properties of Li₂InMo₃O₈ and Li₂ScMo₃O₈.
• To elucidate the distinct ground states of these two triangular lattice compounds using advanced spectroscopic techniques.
• To understand the influence of crystal structure and magnetic interaction anisotropies on their magnetic behavior.

Main Methods:

• Muon spin rotation (μSR) spectroscopy on polycrystalline samples.
• Inelastic neutron scattering (INS) spectroscopy on polycrystalline samples.
• Analysis using the nearest neighbor anisotropic Heisenberg model.

Main Results:

• μSR and INS measurements revealed fundamentally different magnetic behaviors for Li₂InMo₃O₈ and Li₂ScMo₃O₈.
• Li₂InMo₃O₈ exhibits spin wave excitations consistent with a 120° ordered spin structure.
• Li₂ScMo₃O₈ displays short-range magnetic order below 4 K, with persistent quantum spin liquid-like magnetic fluctuations.

Conclusions:

• The ground states of Li₂InMo₃O₈ and Li₂ScMo₃O₈ are markedly different, correlating with their distinct magnetic properties.
• Spin wave excitations in Li₂InMo₃O₈ are well-described by anisotropic Heisenberg model, confirming its conventional magnetic order.
• Li₂ScMo₃O₈'s behavior suggests a quantum spin liquid state, influenced by crystal and interaction anisotropies.