Resonant Photoemission Spectroscopy of Layered Triangular Lattices Ag2MO2 (M = Ni and Mn): Evidence for M 3d States at Fermi Level

Abstract

We report on the soft X-ray photoemission and absorption spectroscopy of Ag 2 NiO 2 and Ag 2 MnO 2 , which consist of alternate stacks of (Ag 2 ) + and ( M O 2 ) - layers. The core-level photoemission and absorption spectra indicate mainly trivalent Ni 3+ in Ag 2 NiO 2 , and trivalent Mn 3+ with an admixture of Mn 2+ states in Ag 2 MnO 2 . The M 2 p –3 d resonant photoemission clearly shows that the density of states at the Fermi level includes the M 3 d character in both compounds. The results indicate that the Ni 3 d and Mn 3 d states at the Fermi level are responsible for the significant mass enhancement of carriers, as seen in the transport properties of Ag 2 NiO 2 and Ag 2 MnO 2 .