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

The Pr3+ 4f2 3H4 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 A40 〈r4〉=6.89±0.30 meV and A60 〈r6〉=0.24±0.10 meV.