Magnetic structures of TbTX compounds

TbTX (T = Ir, Pt and X = Si, Ge, Ga) compounds crystallize in the orthorhom bic TiNTiSi-type of crystal structure and art: antiferromagnets with a Neel temperature of 32 Ii for TbIrSi, 24 K for TbIrGe and 15 K for TbPtGe and t he sine-modulated magnetic ordering with the propagation vector k = (0, k(y ), 0) is observed. The y-component of the propagation vector is 0.4093 for T = Tr and 0.7155 for T = Pt and 0.2938 for TbIrSi. The Tb magnetic moment is parallel to the a-axis in TbIrSi, c-axis in TbIrGe and b-axis for TbPtGe . In TbPtSi a complex magnetic ordering is observed, while in TbPtGa at T = 1.5 Ii the magnetic order of ran-earth moments is collinear and described by the propagation vector k = (0, 1/2, 0). With increasing temperature abov e T-t = 18 K, a change into a sine-modulated structure was observed. (C) 20 00 Elsevier Science B.V. All rights reserved.