Phase relationships and structural, magnetic, and thermodynamic properties of the Yb5Si4-Yb5Ge4 pseudobinary system

The crystallography, phase relationships, and physical properties of the Yb5SixGe4−x alloys with 0⩽x⩽4 have been examined by using single crystal and powder x-ray diffraction at room temperature, and dc magnetization and heat capacity measurements between 1.8K and 400K in magnetic fields ranging from 0 and 7T. Unlike the majority of R5SixGe4−x systems studied to date, where R is the rare earth metal, all Yb-based germanide-silicides with the 5:4 stoichiometry crystallize in the same Gd5Si4-type structure. The magnetic properties of Yb5SixGe4−x materials are nearly composition independent, reflecting the persistence of the same crystal structure over the whole range of x from 0 to 4. Both the crystallographic and magnetic property data indicate that Yb5SixGe4−x alloys are heterogeneous mixed valence systems, in which the majority (60%) of Yb atoms is divalent, while the minority (40%) is trivalent.