Antiferromagnetic ordering in Cu₂OCl₂studied by the muon spin rotation/relaxation technique

Abstract

We report on muon spin rotation/relaxation (µSR) studies of the cuprate mineral melanothallite, Cu2OCl2, over a temperature range between 4.1 and 300 K. This compound has a pyrochlore-like corner-shared OCu4 tetrahedral network with an S = 1/2 system. The magnetic susceptibility shows a broad maximum around 140 K and drops at 70 K. In the µSR measurement, we observed clear muon spin precession spectra below 70 K that is evidence for a long-range magnetic ordered state. However, the time spectra also exhibit exponential damping even in the ordered state, suggesting a possible influence of geometrical frustration in this compound. This renders the need for careful examination of the magnetic structure of the ordered state.