Valence State of Europium in EuCuGa, EuAgGa and EuAuGa Compounds
In most of their alloys and intermetallic compounds, the rare earth ions occur in a trivalent valence state. However, some of the rare earth ions are capable of exhibiting more than one valence state. This happens in the case of Ce, Sm, Eu, Tm and Yb. Apart from the normal trivalent state, the cerium ions exhibit a valence state of 4+, and the remaining four rare earth ions exhibit a valence state of 2+. In some cases, the rare earth ion fluctuates between the two valence states. The phenomenon of valence fluctuation  reflects in an almost temperature independent susceptibility at low temperatures, a near absence of magnetic ordering (except in a few cases), two sets of lines in the XPS spectra, large value of the electronic specific heat coefficient, and in the case of valence fluctuating Eu ions, moderate to strong temperature dependence of the Mossbauer isomer shift.
KeywordsFurnace Europium Argon Cerium CeCu
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