Comparison of the electronic structure of LnBaCo2O5+δ (Ln = Gd, Dy; Ln-112) and LnBaCo4O7 (Ln = Yb; Ln-114) single-crystal surfaces using resonant photoemission

▶ We study rare-earth cobaltites LnBaCo2O5+δ (Ln = Gd, Dy) and LnBaCo4O7+δ (Ln = Yb). ▶ Resonant photoemission is used to identify the valence band states. ▶ States close to the Fermi energy are of mixed O 2p/Co 3d character. ▶ A state at 2 eV binding energy is absent when only tetrahedral Co3+ is present. ▶ Gradual changes are observed at the metal-insulator transition in DyBaCo2O5+δ.