Positive muons in rare-earth dideuterides

mu SR measurements have been performed in the beta-phase rare-earth dideute rides HoD2.0, HoD2.12, DyD2.0, and DyD2.13. For the two Ho compounds and fo r DyD2.0 the temperature dependences of the zero-field (ZF), longitudinal-f ield (LF), and transverse-field (TF) relaxation rates lambda(i) are similar . One can define a 'critical' temperature at which a rate lambda(i) peaks. This temperature T-ci roughly corresponds to the magnetic transition temper ature found in balk magnetic measurements. Above T-ci, where practically th e full mu SR-signal asymmetry is observed, the rates lambda(i) are describe d by alpha(i)/T - T-ci/(-beta i) + lambda(0i). Below T-ci only a reduced fr action of the muons is visible in the signal. For DyD2.13 zero-field and lo w-transverse field measurements show that already below similar to 300 K on ly a reduced and variable fraction of the muons contribute to the signal. B elow similar to 10 K, a weak spontaneous oscillation of approximate to 90 M Hz is found, but it does not explain the important missing asymmetry. One h as to postulate the existence of short-range order magnetism also at higher temperatures. In HoD2.12 the Knight shift K-mu of the TF mu SR signal is o bserved between 200 and 300 K. K-mu varies linearly with the susceptibility of the compound. (C) 2000 Elsevier Science B.V. All rights reserved.