Mixed valence on dilute Eu in YCu2Si2

We report measurements of electrical resistivity, thermopower, thermal conductivity, magnetic susceptibility, Mößbauer andL _III x-ray absorption of intermediate valent Eu in Y_1–x Eu _x Cu₂Si₂ alloys withx=0.03,x=0.07 andx=0.10. A qualitative comparison of the physical properties of dilute Eu in YCu₂Si₂ with concentrated Eu in EuCu₂Si₂ shows only slight differences; the dominant feature is a very strong variation of the Eu valence with temperature, from about 2.8 at 4 K to about 2.45 at 800 K, in the concentrated compound as well as in the dilute alloys.