EuIr2Si2: a new intermediate valence compound

Abstract
Measurements of 151Eu Mossbauer spectra and magnetic susceptibility show that the europium 4f configuration in EuIr2Si2 changes continuously as a function of temperature from 4f6.2 at 4.2K to 4f6.7 at 290K. By contrast, europium in EuRh2Si2, EuPt2Si2, EuRhSi3 and EuIrSi3 remains divalent. Chemical systematics of the appearance of intermediate valence in ternary europium silicides are discussed.