On anti-decoupling phenomena in LF-muSR

The dynamical properties of local dipole fields in a model of a dilute triangular lattice antiferromagnet LuFeMgO4 have been investigated for the purpose of understanding the origin of the unique anti-decoupling effect in longitudinal field (LF)-muSR. In this compound the decay of muon polarization is noticeably faster in LFs than in a zero field in a certain temperature region slightly above the magnetic transition. Our modified lattice model, which reproduces the observed magnetic properties remarkably well, predicts a strong influence of the external field on the long-term behavior of the spins, and consequently on the long-term behavior of the local dipole fields for the muons. The conditions for observing this unique effect in the muSR time-window were considered. The antiferromagnetic inhomogeneity that enhances the susceptibility and the characteristic connectivity in dilute lattices near the percolation would be important factors.