Magnetic properties and electronic structure of R3T4X4 (R: La–Nd, Gd–Er; T: Mn, Cu; X: Ge, Sn) compounds

Abstract

The results of magnetic and neutron diffraction studies of a new series of intermetallic compounds R3T4X4 (R: La–Nd, Gd–Er; T: Mn, Cu; X: Ge, Sn) are presented. These compounds crystallize in the orthorhombic Gd3Cu4Ge4-type structure (space group Immm). The rare earth atoms occupy two non-equivalent crystallographic positions. All the investigated compounds are antiferromagnets. In the R3Mn4Sn4 series the rare earth and the manganese magnetic moments order at different temperatures: the rare earth moments order at 25K (R: Pr) and 60K (R: Nd), while the manganese moments order at 300K (La), 230K (Pr) and 210K (Nd). The R3Cu4Ge4 compounds are antiferromagnets with Néel temperatures between 23K (for Tb3Cu4Ge4) and 5.9K (for Er3Cu4Sn4). For Tb3Cu4Ge4, Er3Cu4Ge4, Ho3Cu4Sn4 and Er3Cu4Sn4 further phase transitions occur below the Néel temperature. The magnetic moments are localized only on the rare earth atoms. The moments located at different crystallographic sites have different values and order at different temperatures. The electronic structure of Gd3Cu4X4 (X: Ge, Sn) was studied by X-ray photoemission spectroscopy (XPS). The complex character of the valence band influences the magnetic properties of these compounds.