MUON SPIN RELAXATION IN YMN2DX DEUTERIDES

Zero- and longitudinal-field muon spin relaxation techniques have been used to study spin fluctuations in YMn2D and YMn2D2 compounds in the temperature range 10-300 K. The temperature dependence of the asymmetr y parameter indicates a first-order transition to ferrimagnetism at T- c = 220 K and 260 K for YMn2D1 and YMn2D2, respectively. In contrast t he depolarization rate lambda(T) exhibits a critical divergence, chara cteristic of a continuous transition, as T-c is approached from above. These features are consistent with those observed for the parent comp ound YMn2 and indicate that the character of the spin fluctuations in the paramagnetic state changes little with deuterium loading, despite marked modifications to the low-temperature, magnetically ordered stat e. lambda(T) provides evidence of significant spin fluctuations below T-c, while slight deviations from predicted behaviour indicate further structural or magnetic transitions in the ordered state.