ELECTRONIC-STRUCTURE OF T-STAR-TYPE ND1.4CE0.2SR0.4CUO4 STUDIED BY PHOTOELECTRON-SPECTROSCOPY

We present investigations of the electronic structure of T*-type Nd1.4Ce0.2Sr0.4CuO4 by means of photoelectron spectroscopy. The Cu-O-hybridization for Nd1.4Ce0.2Sr0.4CuO4 seems to have a smaller value than in n-doped T'-HTSCs, but is slightly larger than e.g. for Bi2Sr2CaCu2O8-delta. We attribute this to the structural properties of these compounds. On the other hand, the effective Coulomb repulsion on the copper site for T* is found to be comparable to the electron doped systems. Concerning the mean Nd-O-hybridization within the rare-earth layers only small differences between Nd1.4Ce0.2Sr0.4CuO4 and T'-systems are observed. Doped Ce was confirmed to be tetravalent in both T'- and T*-compounds. The Cu-O-valence band region shows no significant changes compared with other HTSCs.