Critical Slowing Down in Zn-Mg-Ho Quasicrystal

By means of longitudinal field muon-spin spectroscopy, we have found a clear critical slowing down caused by spin fluctuation of Ho moments in the icosahedral quasicrystal (QC), i-ZnMgHo, with freezing temperature (Tf =1.95 K), for which the susceptibility showed an anomaly at5K. The difference is attributed to crystalline elec-tric field (CEF) effects. The muons experience a broad, fluctuating, field distribution, of width Δ ∼6.3Taround Tf . The effect of the CEF is also apparent in zero field and weak applied transverse field measurements, with an onset around 60 K. For the Cd-based QCs (CdMgHo and CdMgGd), which exhibited two freezing temperatures in the susceptibility, the change in fluctuation rate, i.e. freezing, occurs at the lower Tf .