Substitution effects on mixed valence in ternary intermetallics

We report here the changes in the europium valence in Eu 1−x Ln x Pd 2 Si 2 (LnLa, Y, Yb; 0 x - III absorption edge spectroscopy. On the basis of the simple unit-cell volume considerations and from the fact that the unit-cell volume of EuPd 2 Si 2 is intermediate between that of LaPd 2 Si 2 and Y(Yb)Pd 2 Si 2 , one expects the europium valence to vary in both cases as a function of x , with the variation taking place in the opposite directions in the two pseudoternaries Eu 1−x La x Pd 2 Si 2 and Eu 1−x Y(Yb) x Pd 2 Si 2 . However, we find that the valence does not change as a consequence of lanthanum substitution and increases with the addition of yttrium (ytterbium). These results are discussed in terms of the local environment of europium atoms in these systems.