On the atomic and magnetic ordering of hexagonal NdCuSn

The magnetic structure of the hexagonal stannide NdCuSn has been studied by neutron powder diffraction at low temperature. Magnetic ordering occurs be low similar to 10 K and is associated with two magnetic wave vectors, q(1) = (0, 3/8, 0) and a = (1/2, 0, 0) or (0, 1/2, 0). The q(1) vector is attrib uted to a majority fraction (>90%) of the NdCuSn phase having an ordered Cu /Sn sublattice (non-centrosymmetric NdPtSb type structure, space group P6(3 )mc). It can be described as originating from a transverse sine wave modula ted arrangement of spins oriented \\ c with a maximum moment value of 2.2 m u(B)/Nd atom, or alternatively by an antiphase domain structure having two amplitudes. The q(2) vector is attributed to a minority fraction (<10%) of the NdCuSn phase having a disordered Cu/Sn sublattice (centrosymmetric CaIn 2 type structure, space group P6(3)/mmc). It has a simple antiferromagnetic +- moment arrangement along a or b and the moments are oriented \\ c with a refined value of about 1.2 mu B.