Crystal-field spectrum and linewidths in the heavy-fermion system ${\mathrm{PrInAg}}_2$

The heavy-fermion intermetallic compound ${\mathrm{PrInAg}}_2$ has been studied by means of inelastic neutron scattering. In agreement with a previous study, there is clear evidence from both the excitation energies and relative intensities that the crystal-electric-field ground state is the ${\Gamma }_3$ nonmagnetic, non-Kramers doublet, and this, together with enhanced thermodynamic properties at low temperatures, indicates that ${\mathrm{PrInAg}}_2$ is a candidate quadrupolar Kondo material. In addition to the ${\Gamma }_3-{\Gamma }_4$ and ${\Gamma }_3-{\Gamma }_5$ excitations, which are seen at low temperature, we have observed the other two allowed transitions, ${\Gamma }_4-{\Gamma }_1$ and ${\Gamma }_4-{\Gamma }_5,$ which are visible when the ${\Gamma }_4$ triplet becomes thermally populated. Within the Lea-Leask-Wolf parametrization scheme, we obtain $W=-0.111\pm 0.006\mathrm{meV}$ and $x=-0.079\pm 0.037,$ values that are similar to but slightly different from those previously reported. No magnetic quasielastic scattering is seen, down to ∼90 μeV, and this provides further evidence that the heavy-fermion behavior is unconventional and has a nonmagnetic origin. However, both the ${\Gamma }_3-{\Gamma }_4$ and ${\Gamma }_3-{\Gamma }_5$ levels are broadened significantly and to differing degrees. Possible sources of this broadening are discussed.