Penetration depth study of CeIrIn$_{5}$

The heavy-Fermion compounds CeTIn$_{5}$, with T a transition metal, provide a fertile ground for studying the interplay between magnetism and superconductivity. The T = Co compound has a transition temperature $T_{c }$ = 2.4 K, and has a d-wave order parameter. As Ir is substituted for Co, the transition temperature decreases sharply to T$_{c}$ = 0.4 K. One report of the thermal conductivity of CeIrIn$_{5}$ supports a d-wave state, another argues in favor of a hybrid gap state with broken time-reversal symmetry. We report penetration depth studies of CeIrIn$_{5}$ to $T_{c}/$5 that supports the d-wave scenario. Converted to superconducting fraction, the data taken with the \textit{rf }measuring field along various crystallographic axes can be scaled to collapse to a single curve that matches a d-wave calculation with a zero-temperature gap of 2.5k$_{B}$T$_{c}$.