The magnetic properties of the ternary intermetallic RPtGa (R = Gd-Er) compounds

Neutron diffraction and magnetometric data for the RPtGa compounds (R = Gd- Er) are presented. These compounds crystallize in the orthorhombic TiNiSi-t ype structure. The crystallographic space group is Pnma. The temperature de pendence of the magnetic susceptibility indicates that these compounds are antiferromagnets with the Neel temperature between 23 K for GdPtGa and 3.2 K for ErPtGa. The structural parameters and the magnetic structures of RPtG a (R = Tb-Er) compounds have been determined on the basis of neutron diffra ction data. At 1.5 K, TbPtGa and 21 and DyPtGa exhibit a collinear magnetic structure described by the wave vector k = (0, 1.2, 0). The magnetic momen ts are located on the rare-earth ions. Increase of temperature above T-1 = 18 K for TbPtGa and above 7 K for DyPtGa, leads to a change of this structu re into a sine-modulated one. The collinear magnetic order in HoPtGa descri bed by the wave vector k = (1/2, 1/2, 0) at 1.5 K changes into a sine-modul ated structure at T-t = 2.4 K. In ErPtGa a sine-modulated structure exists between 1.5 K and the Ni el temperature of 3.2 K. (C) 2000 Elsevier Science B.V. All rights reserved.