Resonant photoemission and correlated satellites in K2CoF4

Resonant photoemission experiments at the Co 3p-->3d absorption threshold are used to identify the correlated satellites in the one-electron removal spectrum of the valence band of the two-dimensional Ising antiferromagnet K2CoF4. In addition, x-ray photoelectron spectra of the core levels, interpreted by a configuration-interaction impurity-cluster model, are reported. The estimated charge transfer Delta and the Mott-Hubbard U charge fluctuations pose K2CoF4 in the Mott-Hubbard region of the Zaanen-Sawatzky-Allen diagram. The values of Delta and U are also used to estimate the superexchange parameter J by considering a metal-ligand-metal three-center model. The results for K2CoF4 are compared to those obtained for CoO and the effect of Delta on the photoemission spectral features and on the magnitude of J are discussed.