Abstract
Mössbauer spectroscopy, X-ray photoemission spectroscopy and magnetization studies of EuCu2−x Fe x Si2, EuCu2Si2−x Ge x , EuCu2−x Si2+x , and EuNi2−x Si2+x have been performed. In EuFe2Si2 and EuNi2Si2 the Eu ion is trivalent, in EuCu2Si2 it is of intermediate valency. In all systems withx=0, many inequivalent Eu sites of intermediate valency are formed. In EuCu2−x Fe x Si2, the average valency of Eu moves nonmonotonically toward Eu3+. In EuCu2Si2−x Ge x , EuCu2−x Si2+x and EuNi2−x Si2+x , the Eu average valency moves quickly towards Eu2+. In all three systems, whenx=1, all Eu ions are already stable divalent. The systems EuCuSi3 and EuNiSi3 order magnetically at 40 K and 34 K, and exhibit hyperfine fields of 323 kOe and 458 kOe, respectively. XPS and Mössbauer isomer shift determinations of the average Eu valence as a function of temperature in EuCu1.5Fe0.5Si2 are in good agreement. The experimental observations concerning the Eu valencies can not be explained solely in terms of the local volume available to the Eu ion; the nature of chemical environment plays a dominant role.
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Nowik, I., Felner, I. & Wertheim, G.K. Europium valency in EuCu2−x Fe x Si2, EuCu2Si2−x Ge x , EuCu2−x Si2+x and EuNi2−x Si2+x . Hyperfine Interact 33, 145–159 (1987). https://doi.org/10.1007/BF02394105
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DOI: https://doi.org/10.1007/BF02394105