Crystal Field Effects in CeIrIn₅

In this work, we study crystalline electric field effects in the heavy fermion superconductor CeIrIn₅. We observe two regions of broad magnetic response in the inelastic neutron scattering (INS) spectra at 10 K. The first corresponds to the transition between the Γ₇ groundstate doublet and the first excited state doublet at 4 meV interwoven with a broad quasielastic contribution. The second region corresponds to the transition between the ground state and the second excited state doublet at 28meV. The large Lorentzian half-widths of the peaks (∼10 meV) calls into question calculations for the specific heat and magnetic susceptibility that assume sharp crystal field (CF) levels. Consequently, we have calculated the INS spectra and magnetic susceptibility using the Anderson impurity model within the non-crossing approximation including the effects of CF level splitting.