Magnetic ordering of ScMn6Ge6 by neutron diffraction

The compound ScMn6Ge6 (HfFe6Ge6-type, P6/mmm) orders antiferromagnetically below TN=516 K. Neutron powder diffraction at various temperatures 1.5-309 K shows the existence of two distinct magnetic ordering ranges described by the commensurate q1=(0, 0, 1/2) and the incommensurate q2=(0, 0, qz) vectors: (i) the HT (high temperature) Tt≈100 KT>1.5 K range has an easy double-cone incommensurately modulated structure described by two vectors (q1, q2). At 1.5 K q2=(0, 0, 0.405(1)), the spiral angle is Φ=145.8° the cone half angle is α≈8° and the ordered moment value μMn=2.12(2) μB is the same as for the isomorphic RMn6Ge6 (R=heavy rare earth) compounds. The 1.5 K q2 satellites are very weak as the in-plane moment component measures only 0.31 μB.