Muon spin relaxation in ErRh4B4

Data on zero‐field μSR in ErRh4B4 are presented for temperatures from 4 to 300 K. Due to the large erbium moment, most of the muons have a relaxation time of less than 10 ns for temperatures below about 50 K. The data have been analyzed in terms of two distinct muon sites in the material. The deduced erbium relative fluctuation rate versus temperature is related to the crystalline electric field levels of erbium in the RERh4B4 structure.