Anomaly of the quadrupole interaction in mixed-valenceEuPd2Si2

Abstract

The homogeneous mixed-valence compound ${\mathrm{EuPd}}_2$ ${\mathrm{Si}}_2$ has been studied thoroughly at temperatures 4.2 K≤T≤292 K with use of the ${}_{}{}^{151}{}_{}{}^{}\mathrm{Eu}$ Mössbauer effect. In the temperature region of the valence transition at T≊160 K a maximum of the quadrupole interaction and of the linewidth has been observed. This effect is attributed to an enhanced admixture of 4f contributions to the conduction-electron states, which therefore exhibit stronger non-s character. At T=160 K and in an external magnetic field of 12.8 T, a small field-induced valence shift towards ${\mathrm{Eu}}^{2+}$ has been observed, as indicated by a change of the isomer shift of ΔS=0.20(4) mm/s.