Search for the muon-stopping sites in rare-earth orthoferites [i.e. orthoferrites] by means of dipolar calculation

Abstract

The uSR data for RFe03 (R=Er, Ho, Y, Dy, Eu and Sm) indicates that three separate localized muon sites may exist. In Ref.(12) one of these sites lying in the R-0 plane of the perovskite structure was identified, hereafter referred to as the Holzschuh-1 site.

We have performed dipole sum calculations of the internal fields in the orthoferrites for the magnetic orderings present within the series. Using a weighting scheme requiring a match to the experimental values for the magnitude and directions of internal fields from observed uSR signals, and a muon-oxygen distance consistent with bond formation, we have verified the Holzschuh-1 site and have identified two additional muon-oxygen bonding sites. The three sites thus located provide a satisfactory explanation for all of the uSR signals reported in the orthoferrite series. The two newly identified sites, which we have called ''Holzschuh-2 and Hofmann sites" are associated with the corner oxygen of the rare-earth oxygen plane in the pseudolattice picture (Fe=origin). At higher temperatures, increased muon motion results in migration of muons to the more stable Holzschuh-1 site, so that only one signal is seen.