Crystal structure and magnetic properties of R3Fe0.5GeS7 (RÂ =Â Y, La, Ce, Pr, Sm, Gd, Tb, Dy, Ho, Er and Tm)

The crystal structure of quaternary compounds R3Fe0.5GeS7 (R = Y, La, Ce, Pr, Sm, Gd, Tb, Dy, Ho, Er and Tm) was determined by means of single-crystal and powder X-ray diffraction methods. It is of the hexagonal La3Mn0.5SiS7 type (space group P63, Pearson symbol hP23) The R atoms occupy trigonal prisms capped with two additional atoms, the Fe atoms are located inside octahedra, and the Ge atoms have tetrahedral environment. Magnetic properties of the compounds R3Fe0.5GeS7 (R = Ce, Pr, Sm, Gd, Tb, Dy, Er and Tm) were studied down to 1.72 K. Their magnetic behaviour results from combined contributions due to R3+ and Fe2+ sublattices. In each material magnetic exchange interactions are dominated by antiferromagnetic correlations. In most of them, the exchange interactions give rise to long-range magnetic orderings at low temperatures.