The interplay between geometric frustration, spin-orbit coupling, and structural disorder can give rise to unconventional magnetic ground states in rare-earth triangular-lattice magnets. We report low-temperature magnetic and ${}^7\mathrm{Li}$ NMR investigations of the disordered triangular-lattice compound ${\mathrm{LiCaYb}}_5({\mathrm{BO}}_3{)}_6$ (LCYBO). Rietveld refinement confirms a hexagonal $P{6}_{5}22$ structure with partial Ca/Yb antisite disorder and fractional Li occupancy. Magnetic susceptibility and magnetization measurements indicate a well-isolated effective $J_{\mathrm{eff}}=1/2$ Kramers doublet with weak antiferromagnetic interactions $({\theta }_{\mathrm{CW}}\approx -0.54\mathrm{K})$. The specific heat reveals a weak anomaly near 0.43 K, suggesting the development of short-range correlated magnetism rather than conventional long-range order. ${}^7\mathrm{Li}$ NMR spectra broaden strongly upon cooling, consistent with increasingly inhomogeneous internal magnetic fields. The spin-lattice relaxation exhibits two relaxation components consistent with disorder-induced distributions of local magnetic environments arising from antisite disorder and competing exchange pathways. Our results establish LCYBO as a structurally disordered frustrated triangular-lattice magnet with correlated low-energy spin dynamics.

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• Specific heat
• Rare-earth magnetic materials
• Triangular lattice
• Magnetization measurements
• Nuclear magnetic resonance