Crystal structure and magnetic properties of R3Co0.5GeS7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Tm) and R3Ni0.5GeS7 (R = Y, Ce, Sm, Gd, Tb, Dy, Ho, Er and Tm)

The crystal structure of quaternary compounds R3Co0.5GeS7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Tm) and R3Ni0.5GeS7 (R = Y, Ce, Sm, Gd, Tb, Dy, Ho, Er and Tm) (La3Mn0.5SiS7 structure type, space group P6(3), Pearson symbol hP23) was determined by means of X-ray single crystal diffraction. The R atoms are located in trigonal prisms with two additional atoms, the Co (Ni) atoms occupy octahedra, the Ge atoms are located in tetrahedra. Magnetic properties of the compounds R3Co0.5GeS7 (R = Sm and Gd) and R3Ni0.5GeS7 (R = Gd, Dy, Er and Tm) were studied down to 1.72 K. Their magnetic behaviour is governed by trivalent rare-earth and divalent transition-metal constituents. In each material, the magnetic exchange interactions are dominated by antiferromagnetic correlations, which promote long-range magnetic orderings at low temperatures. (C) 2015 Elsevier B.V. All rights reserved.