Magnetic, electronic and transport properties of the Ce 3Ag 4X 4 (X=Ge, Sn) compounds

Abstract

The work presents results of magnetometric, transport, XPS and neutron diffraction measurements performed on polycrystalline samples of Ce 3Ag 4X 4 (X=Ge, Sn). The X-ray and neutron diffraction data indicate that these compounds crystallize in an orthorhombic structure of the Gd 3Cu 4Ge 4-type. The magnetometric data reveal a ferromagnetic-like behaviour below 10 K in the case of Ce 3Ag 4Ge 4 and a weak antiferromagnetic-like maximum at 9 K for Ce 3Ag 4Sn 4. The neutron diffraction data do not evidence magnetic ordering in any of the two compounds. Temperature variations of the electrical resistivity and thermoelectric power suggest their metallic character. The Ce 3d X-ray photoemission spectra show that both compounds are mixed valence systems. Analysis of the f 2 peak weight using the Gunnarsson–Schönhammer theory suggests a hybridization constant of 169 meV for Ce 3Ag 4Ge 4 and 82 meV for Ce 3Ag 4Sn 4. The valence band spectra are dominated by the Ag 4d states contributions. Broad and very weak peaks extending between 0 and 4 eV correspond to the Ce 5d6s 2 states.