High Field Knight Shift studies in CeIrIn5

All heavy fermion compounds that have been measured with NMR exhibit a Knight shift anomaly, in which the Knight shift does not scale with the bulk susceptibility below a characteristic temperature, T*.~ Typically this temperature corresponds with the Kondo lattice coherence temperature as measured by other probes.~ In order to investigate the microscopic origin of this anomaly, we have conducted high field measurements of the In-115 Knight shift in CeIrIn5 up to 30 T.~ We find that although the onset temperature T* is field independent, the overall low temperature shift below T* is suppressed.~ In the context of the two-fluid model, these results suggest that that the dominant change is in the local moment channel.