Evolution of the heavy fermion state in Ce2IrIn8

We report μSR Knight shift and susceptibility studies for 1 T applied field along the crystalline c- and a-axes of the heavy fermion compound Ce2IrIn8. Below a characteristic temperature T* one observes a 'Knight-shift anomaly' in which the Knight shift constant K no longer scales linearly with χ. This anomaly is consistent with a scaling law in which the susceptibility χ is composed of a high-temperature component corresponding to non-interacting local moments and a low-temperature component χcf∼(1-T/T*)ln(T*/T) which characterizes the heavy-electron state below T*. We find that T* is anisotropic, with Ta*=59(3)K and Tc*=24(1)K, and derive the magnitudes of χcfa,c.