Magnetic properties of R 3Cu 4X 4 (R=Gd–Er; X=Ge, Sn) compounds

Abstract

In this work, the results of magnetic and neutron-diffraction studies of a new series of intermetallic compounds R 3Cu 4X 4 (R=Gd–Er; X=Ge, Sn) are presented. The X-ray and neutron-diffraction data indicate that these compounds crystallise in the orthorhombic Gd 3Cu 4Ge 4-type structure (space group Immm). In this structure, the rare-earth atoms occupy two non-equivalent crystallographic positions: 2d and 4e. The magnetometric and neutron diffraction measurements indicate that the R 3Cu 4X 4 (R=Gd–Er; X=Ge, Sn) compounds are antiferromagnets with Néel temperatures between 23 K for Tb 3Cu 4Ge 4 and 5.9 K for Er 3Cu 4Sn 4. For Tb 3Cu 4Ge 4, Er 3Cu 4Ge 4 and Er 3Cu 4Sn 4, additional phase transitions are observed below the Néel temperature. The neutron-diffraction data indicate that the magnetic moments are localised only on the rare earth atoms. The moments located at different crystallographic sites have different values and order at different temperatures.