Powder neutron diffraction study of antiferromagnetism in Er6Mn23D23

The compound Er6Mn23D23 has been prepared and a powder neutron diffraction study has been done. The compound is paramagnetic at 3000K and antiferromagnetic at 1500K. The crystallographic space group is I4/mmm with deuterium atoms occupying a, 1, m, n, and o sites. Since Er6Mn23 belongs to the Fm3m space group, deuteration is responsible for a reduction in symmetry. At 1500K the Er and Mn moments in the deuteride are collinear with the c-axis and the Shubnikov magnetic space group is P/sub I/4/mm'm'. This is also different from the non-deuterated Er6Mn23 which has its easy axis along the cubic <111> direction (the tetragonal <101> direction). In the deuteride, the e site Er atoms have moments of 2.5 μ/sub B/ while those on h sites have moments of 1.2 μ/sub B/. The Mn moments are approximately 3 μ/sub B/ for the b and c sites and approximately 1 μ/sub B/ for the two n sites. The Mn atoms on the f sites cannot have ordered moments due to the symmetry of the magnetic space group and, indeed, none is found. Magnetic susceptibility measurements are also reported