The magnetism of Sm3Ag4Sn4 and Gd3Ag4Sn4

The magnetic properties of the ternary intermetallic compounds Sm3Ag4Sn4 and Gd3Ag4Sn4 are presented. Both phases crystallise in the orthorhombic oI22-Gd6Cu8Ge8 type structure, space group Immm, and, from dc magnetisation measurements, display antiferromagnetic ordering at low temperatures: TN = 9K for Sm3Ag4Sn4 and 8K for Gd3Ag4Sn4. ac susceptibility measurements are in good agreement with the antiferromagnetic transition of the Sm compound (TN = 9.1 K), while two different transitions are observed in the thermal behaviour of χac for Gd3Ag4Sn4 at 22 and 8.2 K. Isothermal magnetisation measurements at 5K confirm the antiferromagnetic ground state of the compounds. In the paramagnetic region Gd3Ag4Sn4 follows the Curie–Weiss law (μeff. = 7.77 muB and θp = −64 K), while the non-Curie–Weiss behaviour of the Sm phase is discussed in terms of partial occupation of the low-lying J = 7/2 excited state by the Sm3+ ions. The values of the ordering temperatures of the two compounds do not seem to follow the de Gennes scaling.