Magnetic structures of ternary rare-earth compounds, TbNiSn and DyNiSn

Single-crystal neutron diffraction studies have been performed on the rare- earth ternary compounds, TbNiSn and DyNiSn, Both crystals exhibit an incomm ensurate magnetic structure expressed by the propagation vector, Q = (Q(x), Q(y), 0) and its higher harmonics at low temperatures: for TbNiSn, Q = (0, 600, 0.345, 0) with its third and fifth harmonics, and for DyNiSn, Q = (0.6 41, 0.340, 0) with its third harmonics. Both propagation vectors are a litt le temperature-dependent, and for TbNiSn at 6 K it becomes nearly commensur ate of about (2/3, 1/3, 0), In an external magnetic field TbNiSn shows comm ensurate modulation with Q = (2/3, 0, D) at 4.2 K along the easy magnetizat ion direction of the b-axis. (C) 1999 Elsevier Science Ltd. All rights rese rved.