Untersuchung des MÖSSBAUER-Effekts in Elpasolithen A2 INaFeF6.

Abstract

57Fe-MÖSSBAUER spectra of the cubic elpasolithes A2 INaFeF6 (AI = K, Rb, Cs) show strong single line broadening in the temperature range 4.2 K ≤ T ≤ 600 K. This broadening is attributed to a statistical distribution of differently distorted FeF6 3-octahedra, causing a statistical distribution of electric fieldgradients at the 57Fe-position. With the aid of a model calculation it was tried to estimate the order of the octahedral distortion. For the compound Rb2NaFeF6 normal to the cell axis an anion displacement of Δ q = 0.11 Å from the regular octahedral position was derived from the Mössbauer data. This value agrees with the root mean square displacement ū = 0.13 Å, which results in this direction from the strongly anisotropic fluorine temperature factors found by X-ray structure determination.