Magnetic, electronic and transport properties of the Ce3Ag4X4 (X=Ge, Sn) compounds

The work presents results of magnetometric, transport, XPS and neutron diffraction measurements performed on polycrystalline samples of Ce3Ag4X4 (X=Ge, Sn). The X-ray and neutron diffraction data indicate that these compounds crystallize in an orthorhombic structure of the Gd3Cu4Ge4-type. The magnetometric data reveal a ferromagnetic-like behaviour below 10 K in the case of Ce3Ag4Ge4 and a weak antiferromagnetic-like maximum at 9 K for Ce3Ag4Sn4. 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 f2 peak weight using the Gunnarsson-Schönhammer theory suggests a hybridization constant of 169 meV for Ce3Ag4Ge4 and 82 meV for Ce3Ag4Sn4. 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 5d6s2 states.