Neutron diffraction study, magnetic properties and thermal stability of YMn2D6 synthesized under high deuterium pressure

A new phase YMn2D6 was synthesized by submitting YMn2 to 1.7 kbar deuterium pressure at 473 K. According to X-ray and neutron powder diffraction experiments, YMn2D6 crystallizes in the Fm (3) over barm space group with a = 6.709(1) A at 300 K. The Y and half of the Mn atoms occupy statistically the 8c site whereas the other Mn atoms are located in 4a site and surrounded by 6 D atoms (24e). This corresponds to a K2PtCl6-type structure with a partially disordered substructure which can be written as [YMn]MnH6. No ordered magnetic moment is observed in the NPD patterns and the magnetization measurements display a paramagnetic behavior. The study of the thermal stability by Differential Scanning Calorimetry and XRD experiments indicates that this phase decomposes in YD2 and Mn at 625K, and is more stable than YMn2H4.5. (C) 2004 Elsevier Inc. All rights reserved.