A switch from ferro- to antiferromagnetic ordering in the solid solutions CeAuGe_1-xSn_x

CeAuGe and CeAuSn (both NdPtSb type, space group P6(3)mc) form a complete solid solution CeAuGe1-xSnx with Vegard-type behavior of the cell volume. Samples with steps of x = 0.1 were synthesized from the pure elements by arc-melting. The structure of CeAuGe0.13(2)Sn0.87(2) was refined from single-crystal X-ray diffractometer data: a = 469.10(6), c = 773.90(10) pm, wR(2) = 0.0359, 251 F-2 values and 12 variables. The induced structural disorder caused by the Ge/Sn mixing affects the magnetic ground state of the cerium ions. From the germanium-rich side, the Curie temperature of CeAuGe (10.0 K) decreases towards CeAuGe0.6Sn0.4, while the Neel temperature of CeAuSn (4.4 K) decreases at the tin-rich side toward CeAuGe0.4Sn0.6. The switch of the magnetic ground state occurs approximately around the Ge/Sn ratio of 1:1. Sn-119 Mossbauer spectra of CeAuGe0.1Sn0.9 and CeAuGe0.7Sn0.3 confirm the presence of single crystallographic tin sites in both cases, and the isomer shifts are comparable to that of pure CeAuSn, indicating similar electron density distribution at the tin nuclei.