XAS-STUDIES OF 1/2/2 TRANSITION-METAL COMPOUNDS

X-ray absorption spectroscopy (XAS) investigations of the electronic structure of 4d transition metal (T) based materials are presented. The sensitivity of the white line (WL) feature at the T-L2, 3 edges to the above E(F), d-component of the electronic states is first emphasized with a study of the 4d row elements Mo to Ag. This WL based method is then extended to a systematic study of RT2X2 compounds with: R = Gd or Ce; T - Ru, Rh, Pd and Ag; and X = Si, Ge, and Sn. A central interpretation proposed for the 1:2:2 compounds is the identification of a near edge XAS feature with T(4d)-X anti-bonding states split above E(F) by hybridization. The strength and splitting of this feature are found to decrease in the sequence X = Si-->Ge-->Sn, consistent with the decreasing bonding interaction. A second interpretation proposed is the decrease of T(4d) states at E(F) in these compounds relative to the elements.