Spectroscopic Determination of Crystal-Field Levels of Pr3+ in the Paramagnetic Metallic Compound PrBi

The Pr³⁺ 4f^{2 3}H₄ manifold is split by an octahedral crystal field into four levels Γ₁, Γ₃, Γ₄, and Γ₅. Transitions between these levels in PrBi have been measured using neutron time‐of‐flight spectrometry. Peaks in the observed spectra corresponding to crystal‐field transitions are identified both by their temperature dependence and by comparison with corresponding data from (nonmagnetic) LaBi. Well resolved crystal‐field transitions are observed at 11.7 and 5.8±0.6 meV at 90°K. Additional scattering observed at room temperature is consistent with unresolved transitions at 7.6 and 4.1 meV. As it is known from magnetic measurements that the Γ₁ singlet lies lowest, these four transitions may be identified as Γ₅ to Γ₄, Γ₄ to Γ₁, Γ₅ to Γ₃ and Γ₃ to Γ₄ respectively, thus accounting for all transitions allowed by magnetic‐dipole selection rules. These data give the parameters $A_4^0{\mathrm{〈r}}^4\text{〉=6.89±0.30\hspace{0.17em}}\mathrm{meV}$ and $A_6^0{\mathrm{〈r}}^6\text{〉=0.24±0.10\hspace{0.17em}}\mathrm{meV}$ .