ArXiv · 2026
We use inelastic neutron scattering (INS) to determine the crystal electric field (CEF) excitations of Yb³⁺ in the rare-earth hyperkagome magnet Yb₃Sc₂Ga₃O₁₂. Three nearly dispersionless magnetic excitations are observed near 58, 68, and 74 meV, corresponding to transitions from the ground-state Kramers doublet to the three excited doublets of the J=7/2 multiplet. A Stevens-operator analysis constrained by the local 222 (D₂) symmetry reproduces the excitation energies and spectral weights and yields an Ising-type ground-state g tensor. The first excited doublet lies approximately 58 meV above the ground state, establishing a well-isolated effective J_eff=1/2 degree of freedom over the low-temperature regime relevant to collective magnetism. Notably, the directly measured CEF spectrum substantially revises the level scheme previously inferred from bulk measurements, while preserving the essential low-energy pseudospin description. Two independent fitting protocols give consistent excitation energies, ground-doublet wave functions, and g tensors, despite the nonuniqueness of the individual CEF parameters. The resulting single-ion model also reproduces the characteristic susceptibility, magnetization, and field evolution of the Schottky anomaly in specific heat. These results establish the microscopic single-ion basis needed to construct an effective exchange Hamiltonian and to interpret future measurements of low-energy collective excitations in Yb₃Sc₂Ga₃O₁₂.
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