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

Abstract Neutron diffraction and magnetometric data for the RPtGa compounds (R=Gd–Er) are presented. These compounds crystallize in the orthorhombic TiNiSi-type structure. The crystallographic space group is Pnma. The temperature dependence 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 RPtGa (R=Tb–Er) compounds have been determined on the basis of neutron diffraction data. At 1.5 K, TbPtGa and DyPtGa exhibit a collinear magnetic structure described by the wave vector k =(0, 1 2 , 0) . The magnetic moments are located on the rare-earth ions. Increase of temperature above T t =18 K for TbPtGa and above 7 K for DyPtGa, leads to a change of this structure into a sine-modulated one. The collinear magnetic order in HoPtGa described by the wave vector k =( 1 2 , 1 2 , 0) at 1.5 K changes into a sine-modulated structure at T t =2.4 K. In ErPtGa a sine-modulated structure exists between 1.5 K and the Neel temperature of 3.2 K.