Valence Transition between Eu^<2+> State and Eu^<3+> State in Eu_xY<1-x>Pd_2Si_2 and Eu_xLa_<1-x>Pd_2Si_2

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In EuPd_2Si_2, the valence transition of Eu atoms between the Eu^<2+> state and the Eu^<3+> state takes place when the temperature of the sample changes. In the present study, we prepared Eu_xY_<1-x>Pd_2Si_2 and Eu_xLa_<1-x>Pd_2Si_2, in which the Eu atoms of EuPd_2Si_2 are systematically substituted by non-magnetic Y or La atoms, and we have measured the magnetic susceptibility x, the electric resistivity p and the thermoelectric power S. We found that the temperature of the valence transition of Eu ions is only very weakly dependent on the alloying concentration x of Eu atoms. In addition, the notable structures of the S(T) curves were observed for these samples, which we understand in term of the anomalies of the relaxation time of conduction electrons interacting with the Eu 4f^7 virtual bound state. In this respect, the valence transition of Eu ions in this study makes a contrast with the Kondo problems of the Ce compounds, where the anomalies of the state density of conduction electrons are their central issue.
社団法人日本物理学会の論文
2003-08-15