Electronic structure of 3d-transition-metal compounds by analysis of the 2pcore-level photoemission spectra

Abstract

The electronic structures of a wide range of transition-metal compounds, including Cu, Ni, Co, Fe, and Mn oxides and sulfides, with metal valences ranging from 2+ to 4+, have been investigated by a cluster-type configuration-interaction analysis of the core-level 2p x-ray photoemission spectra. We show that by including the d-d exchange interaction (retaining only diagonal terms) and an anisotropic metal-ligand hybridization in the model, these spectra can be well reproduced, and so can be used to deduce quantitatively values for the ligand-to-metal charge-transfer energy 5, the on-site d-d Coulomb repulsion energy U, and the metal-ligand transfer integrals T. Systematics for 6 and U are generally consistent with those found from previous valence-band studies and follow expected chemical trends. By using values of 5 and U found from this model, we show that most of the transition-metal compounds studied in this work can be classified in the charge-transfer regime of the Zaanen-Sawatzky-Allen diagram. A few exceptions to these systematics have been found. Small U values found for pyrite-type CoS& and FeS2 and large T values for Mn perovskite oxides, as well as the neglect of other mechanisms such as exciton satellites, may indicate a limitation of the local-cluster model.

Prediction of a quantum anomalous Hall state in Co-decorated silicene

“…The application of a finite on-site Coulomb interaction U is necessary for correctly describing the d electrons of the transition metal atoms, as previous studies suggest that the adsorption geometries and electronic configurations are sensitive to correlation effects [19,20]. A value of U = 4 eV is expected to give appropriate results for the transition metal atoms under consideration [21,22] and, therefore, is employed in our calculations. We have also tested different values of the onsite interaction from 3 to 5 eV without finding any influence on our conclusions.…”

Fingerprints of spin-orbital physics in cubic Mott insulators: Magnetic exchange interactions and optical spectral weights

“…One could attempt to fix these parameters using the atomic value of Hund's exchange J H = 0.9 eV. With = 0.181 it leads to U Ӎ 5.0 eV, quite close to other estimates, 43 while the value of R = 0.6 suggests then that, taking the commonly accepted 43,64 value of the CT energy ⌬ = 5.0 eV, the oxygen Coulomb element is large, U p Ӎ 7 eV. This value of U p is larger than usually obtained U p ϳ 4 eV for oxygen ions, such as, for instance, by analyzing the parameters of the three-band model for CuO 2 planes.…”

Effects of Electron Correlation, Orbital Degeneracy and Jahn-Teller Coupling in Perovskite Manganites

“…From experiments and band calculations, t 0 is considered to be around 0.5 eV andŨ is estimated at several eV. 13,15,14,45,46,47) In the present study, we changeŨ /t 0 as a parameter and discuss its realistic value based on our results. The spring constant k is roughly estimated by the frequency of an oxygen bond stretching phonon at order of 10 or 100 eV.…”

“…In particular, we focus here the following: (i) All the materials are the Mott insulator with a charge gap of order of eV at half filling (one e g electron per Mn site on average), where two-dimensional (2D) anisotropy realizes in spin and orbital orderings, and a cooperative JahnTeller (JT) distortion. 7,11,12,13,15,14) (ii) Upon doping of holes, a metal-insulator (MI) transition occurs from the anisotropic Mott insulator to an isotropic ferromagnetic metal through disordered ferromagnetic insulator. 6,9,16) (iii) In the ferromagnetic metallic state, charge dynamics shows strong incoherence with tiny Drude weight even at low temperatures while the linear specific-heat coefficient γ remains small.…”