Behaviour of Eu Valence in RECu<Subscript>2</Subscript>Si<Subscript>2</Subscript> and REPd<Subscript>2</Subscript>Si<Subscript>2</Subscript> Matrices: Fid-Bau Portal

Behaviour of Eu Valence in RECu2Si2 and REPd2Si2 Matrices

Nagarajan, R. / Sampathkumaran, E. V. / Grover, A. K. / Dhar, S. K.

Abstract Though the field of valence fluctuation is a matured one, the anomalies in the temperature dependence of mean valence of rare earth ions in valence fluctuators are still not understood (1). The first task normally adopted in this direction is to understand qualitatively the differences in the properties of the concentrated and dilute systems. In this respect, the compounds EuCu2Si2 and EuPd2Si2, both crystallizing in the ThCr2Si2-type structure, attracted special attention in the past in view of the interesting temperature dependence of mean valence of Eu (2, 3). The behaviour of Eu in the dilute limit in a few matrices have also been investigated for these two systems (1, 4, 5). For instance, the behaviour of Eu in YCu2Si2 is reported to be similar to that of EuCu2Si2, which was taken as an evidence for the single ion behaviour of Eu valency in EuCu2Si2 (1); on the other hand, Eu in LaPd2Si2 behaves entirely differently from that of EuPd2Si2, thereby suggesting the co-operative nature of the valence behaviour in EuPd2Si2 (4,5). In order to gain better insight into the role of chemical pressure on the valence of Eu in these compounds, we have extended previous studies concerning EuCu2Si2 and EuPd2Si2 in the dilute limit to a few other rare earth host matrices. We view all these results together and we find that volume plays a very dominant role in deciding the valence of Eu in dilute limit of these compunds.