We present Mn $3s$ x-ray photoelectron spectra of manganese oxides with the Mn formal valency from $2+$ to $4+.$ We found that the ${\mathrm{Sr}}^{2+}$ doping or cation deficiency in manganites do not change the Mn $3s$ splitting in manganites with the Mn formal valency from $3.0+$ to $3.3+.$ We suggest that doping holes are localized in O $2p$ states.

We present synchrotron-excited oxygen x-ray $K$-emission spectroscopy ($\text{O}K\alpha$ XES) and oxygen x-ray absorption spectroscopy ($\text{O}1s$ XAS) spectra of transition-metal (TM) oxides MnO, CoO, and NiO. The comparison of oxygen $K$-emission and absorption spectra to valence band photoemission and bremsstrahlung isochromat spectra measurements shows that $\text{O}1s$ XAS is not strongly influenced by the core hole effect, whereas the $\text{TM}2p$ XAS significantly shifts to a lower energy. New and effective methods for determining the band gap and anion-to-cation cation charge-transfer energies of the oxides from the measured spectra are presented and applied, and the combination of O XAS and XES is shown to agree well with the results of numerical electronic structure methods applied to strongly correlated oxides. For MnO, the charge-transfer energy is found to be 6.6 eV and the band gap is 4.1 eV; for CoO, the values are 6.1 and 2.6 eV and for NiO, the values are 5.4 and 4.0 eV.

We investigated the possible formation and segregation of oxygen vacancies near the surface of SnO${}_2$ thin films from oxygen $K$-edge x-ray emission and absorption spectra and found that the distribution of O 2$p$ unoccupied states for ferromagnetic SnO${}_2$ thin films is different from that of postannealed SnO${}_2$ films under oxygen atmosphere showing diamagnetic behavior. This spectroscopic result suggests that oxygen vacancies can be the source of the surface-induced magnetism in SnO${}_2$ thin films. This possibility was then explored by calculating the lowest energy levels of the structural defects (impurities or neutral vacancies) with two localized carriers near the surface of SnO${}_2$ film using a quantum-mechanical approach combined with the image charge method. A magnetic triplet state is found to be the ground state of those defects in the vicinity of the SnO${}_2$ surface, whereas the nonmagnetic singlet is the ground state of bulk SnO${}_2$. Surface-induced ferromagnetic order can appear at room temperature via 2D magnetic percolation once the vacancy concentration is greater than 3 $\times$ 10${}^{16}$ m${}^{-2}$.

In this article we present a detailed study of the electronic structure from various Mn-based Heusler alloys using x-ray photoelectron spectroscopy (XPS) and x-ray emission spectroscopy (XES) techniques. Performing the measurements on the Mn-$2p$ core levels as well as on the valence-band states we arrive at a more or less complete description of the electronic and magnetic properties of these compounds. The experimental Mn-$2p$ spectra have been compared with fully relativistic photoemission calculations, which are based on the solution of the spin-polarized Dirac equation. The almost constant exchange splitting of about 0.35 eV, measured between the different Mn-$2p$ sublevels is explainable in terms of the local magnetic moment at the Mn site. Moreover a strong relationship between the magnetization direction and the line shapes of the calculated Mn-$2p$ core-level spectra has been revealed from our analysis. Depending on the atomic number of the Z element we obtain from XES experiments an increasing localization of the Mn-$3d$ states. Also the interatomic distances in the different alloys seem to play an important rule in this process. To support this result we performed in addition valence-band measurements by applying XP. These data, which agree very well with the corresponding x-ray emission spectra are quantitatively reproduced from first-principle electronic structure calculations.

The delafossite-type ${\mathrm{CuFeO}}_2$ single crystal was studied by means of x-ray emission and x-ray photoelectron spectroscopy. The valence state of Cu ions was found to be $1+,$ whereas Fe ions were found to be trivalent in the high-spin $S=5/2\mathrm{}$ state. The x-ray emission (Cu $L_{\alpha },$ Fe $L_{\alpha },$ and O $K_{\alpha })$ and photoelectron spectra were compared to the results of the local spin density approximation (LSDA) (full-potential linearized augmented plane wave method and linearized muffin-tin orbitals in atomic sphere approximation method) and $\mathrm{LSDA}+U$ calculations. It is found that the maximum of the Cu $3d$ state distribution is localized closer to the Fermi level than that of the Fe $3d$ states. The LSDA calculations contradict the experimental results and do not give a correct description of the Cu and Fe $3d$ positions relative to the Fermi level, and incorrectly predict metallic behaviors (semiconductor observed) and give qualitatively incorrect magnetic properties of ${\mathrm{CuFeO}}_2.$ The $\mathrm{LSDA}+U$ calculations give a much better agreement with the observed valence-band structure, the measured electrical, and the magnetic properties.

The electronic structure of the monoclinic phase of titanium monoxide and a vacancy-free rock-salt phase have been investigated using x-ray photoelectron spectroscopy and x-ray emission spectroscopy techniques. For the investigation of the monoclinic structure type, polycrystalline samples of titanium monoxide were used. The samples of the vacancy-free rock-salt structure have been obtained by annealing monoclinic titanium monoxide at high temperature and pressure. The x-ray powder diffraction pattern of both types of samples revealed single-phase crystals without any substructures. The x-ray photoelectron valence band spectra reveal that the upper, mainly Ti $3d$-derived, part of the valence band is split and that the lower, mostly O $2p$-derived, band exhibits three features. A combined representation of the photoelectron valence band spectrum of the monoclinic phase and O $K_{\alpha },$ Ti $L_{\alpha },$ and Ti $K_{\beta 5}$ x-ray emission spectra shows that titanium and oxygen states are hybridized over almost the full valence band region, without a gap. The valence band of the vacancy-free rock-salt phase was found to be wider than that of the monoclinic phase. The experimentally obtained valence band density of states are compared with recent band structure calculations. In addition, we present spectra of the O $1s$ and Ti $2p$ core levels and show the effects of a gradual oxidation of the sample on these spectra.