We study the underlying chemical, electronic, and magnetic properties of a number of magnetite-based thin films. The main focus is placed onto Fe3O4(001)/NiO bilayers grown on MgO(001) and Nb-SrTiO3(001) substrates. We compare the results with those obtained on pure Fe3O4(001) thin films. It is found that the magnetite layers are oxidized and Fe3+ dominates at the surfaces due to maghemite (gamma-Fe2O3) formation, which decreases with increasingmagnetite layer thickness. For layer thicknesses of around 20 nm and above, the cationic distribution is close to that of stoichiometric Fe3O4. At the interface between NiO and Fe3O4 we find the Ni to be in a divalent valence state, with unambiguous spectral features in the Ni 2p core level x-ray photoelectron spectra typical for NiO. The formation of a significant NiFe2O4 interlayer can be excluded by means of x-ray magnetic circular dichroism. Magneto-optical Kerr effect measurements reveal significant higher coercive fields compared to magnetite thin films grown on MgO(001), and an altered in-plane easy axis pointing in the < 100 > direction. We discuss the spin magnetic moments of the magnetite layers and find that a thickness of 20 nm or above leads to spin magnetic moments close to that of bulk magnetite.

The results of XPS measurements of nanostructured Ti (ns-Ti) prepared with a help of severe plastic deformation (SPD) have been presented. We have measured XPS spectra of core levels (Ti 2p, O 1s, C 1s, F 1s) and valence bands before and after treatment of ns-Ti-implants in HF. The obtained data have been compared with XPS measurements of untreated and acid treated coarse-grained Ti (cg-Ti). According to these measurements the surface composition has not practically been changed by reduction of grains size of Ti-implants. It has been found that the surface of both types of implants is covered with thick TiO2 layer. The acid treatment reduces the surface contamination of ns-Ti and cg-Ti by hydrocarbons and induces better passivation and formation of more thick TiO2 layer. It has been shown that severe plastic deformation not only improves mechanical properties but also preserves corrosion stability of Ti-implants.

XPS measurements of coarse-grained and nanostructured nitinol (Ni(50.2)Ti(49.8)) before and after chemical treatment in hydrofluoric acid (40% HF, 1 min) are presented. The nanostructured state, providing the excellent mechanical properties of nitinol, is achieved by severe plastic deformation. The near-surface layers of nitinol were studied by XPS depth profiling. According to the obtained results, a chemical treatment in hydrofluoric acid reduces the thickness of the protective TiO(2) oxide layer and induces a nickel release from the nitinol surface and an arsenic contamination, and can therefore not be recommended as conditioning to increase the roughness of NiTi-implants. A detailed evaluation of the resulting toxicological risks is given.

The electronic structures of SmScO3, GdScO3, and DyScO3 are investigated by means of x-ray photoelectron spectroscopy, x-ray emission spectroscopy (XES), and x-ray absorption spectroscopy (XAS). A strong hybridization between Sc 3d and O 2p is found, and a contribution of the rare-earth 5d states to this hybridization is not excluded. The band gaps of the compounds are determined by combining XES and XAS measurements. For SmScO3, GdScO3, and DyScO3 the band gaps were determined to be 5.6, 5.8, and 5.9 eV, respectively. Magnetization versus temperature measurements reveal antiferromagnetic coupling at 2.96 (SmScO3), 2.61 (GdScO3), and 3.10 K (DyScO3). For DyScO3 a Rietveld refinement of a 2 K neutron-diffraction data set gives the spin arrangement of Dy in the Pbnm structure (Shubnikov group: Pb(')n(')m(')).

The nearest-neighbor coordination and electronic structure in C:Ni(similar to 30 at.%) nanocomposite films grown by ion beam cosputtering in the temperature range of room temperatue (RT) to 500 degrees C are investigated by the means of extended X-ray absorption fine structure (EXAFS), X-ray absorption near-edge spectroscopy (XANES) and X-ray photoelectron spectroscopy (XPS). The obtained results are correlated with the composite nanostructure published elsewhere and magnetic properties determined by the means of X-ray magnetic circular dichroism (XMCD) and superconducting quantum interference device (SQUID) magnetometry. A combined use of EXAFS, XANES, and XPS shows that a carbidic Ni phase exhibiting only local atomic ordering is formed at low growth temperatures (<= 200 degrees C), while ordered carbidic Ni phase forms at similar to 300 degrees C. Further increase in growth temperature results in the formation of face-centered cubic (fee) Ni with a high degree of crystallinity. On the other hand, Ni incorporation strongly promotes the formation of carbon structures with the prominent peak in C K-edge XANES spectra positioned at 288.5 eV in the whole growth temperature range. The magnetic measurements show no magnetic response for the films grown at RT to 200 degrees C, superparamagnetic behavior for the film grown at 500 degrees C with >90% of the Ni atoms in metallic state, and a weak magnetic response for the film grown at 300 degrees C, indicating the presence of Ni-rich regions within carbon containing Ni nanoparticles with similar to 3% of Ni atoms in metallic state.

The electronic structures of iron oxide and iron disulfide (FeO and FeS2) have been examined using x-ray emission spectroscopy and other core-level spectroscopies. We compare the excitation spectra for charge neutral excitation (x-ray emission) and ionization (photoelectron spectroscopy) at the 2p edge and with final-state 3s holes. At the Fe L-2-edge, the branching ratio of L,6 to La emission is much higher for high-spin FeO than for low spin FeS2, similar to previous observations of Heusler alloys. We suggest that there is a general trend toward high branching ratios for magnetic 3d materials and low branching ratios for nonmagnetic materials. Resonant inelastic x-ray spectra of FeO with 3s final-state holes show a smaller exchange splitting than the corresponding x-ray photoemission spectroscopy spectra with 3s hole states.

The electronic structure of the strongly Coulomb correlated cuprate CuGeO3 has been calculated by the local-density-approximation method (LDA + U). The parameter U was varied from 0 to 8 eV. The results of the band-structure calculations are compared with experimental data obtained by means of X-ray photoelectron and resonant X-ray emission spectroscopy methods (Cu L\(\alpha\) and O K\(\alpha\) X-ray emission spectra). It is established that a LDA + U calculation with U = 4 eV reproduces well the X-ray photoelectron and X-ray resonant emission spectral data.

Experimental studies of x-ray photoelectron and Co Lalpha x-ray emission spectra of the ZnS:Co semiconductor were carried out. It was established that Co ions are present in isovalent Co2+ configuration and that the Co 3d impurity states are localized above the top of the valence band by 1.0 +/- 0.2 eV.

The Mn x-ray emission spectra and x-ray photoemission spectra of Mn-based Heusler alloys Co$_2$MnAl, Co$_2$MnSb and La$_{1-x}$Sm$_x$Mn$_2$Si$_2$ compounds (x=0, 0.8) have been measured and discussed in connection with a value local magnetic moment at Mn site. The spectra peculiarities reflect also the localization degree of 3d valence electrons of 3d metals in considered compounds.

The Mn x-ray emission spectra and x-ray photoemission spectra of Mn-based Heusler alloys Co_2MnAl, Co_2MnSb and La_1-xSm_xMn_2Si_2 compounds (x=0, 0.8) have been measured and discussed in connection with a value local magnetic moment at Mn site. The spectra peculiarities reflect also the localization degree of 3d valence electrons of 3d metals in considered compounds.

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.

The Mn X-ray emission spectra and X-ray photoelectron spectra of Mn-based Heusler alloys Co2MnAl, Co2MnSb and La1−xSmxMn2Si2 rare-earth compounds (x=0, 0.8) have been measured and discussed in connection with a value of the local magnetic moment at Mn site. The spectra peculiarities reflect also the localization degree of 3d valence electrons of 3d metals in the considered compounds and could be used as an indicator of the closeness of the density of states to half-metallic character.

A full study of the electronic structures of FeCr2S4 and Fe0.5Cu0.5Cr2S4 is reported based on x-ray photoelectron spectra (valence band and core levels), x-ray emission spectra (Fe Lα, Cu Lα, Cr Lα, S Kβ1,3 and S L2,3) and ab initio TB-LMTO band structure calculations. In the valence band of FeCr2S4, the Fe 3d states are found to be more localized than the Cr 3d states, which dominate at the Fermi level. In Fe0.5Cu0.5Cr2S4, the distribution of Cr 3d (Cr3+) states is unchanged and the Cu ions were found to be in the Cu+ state.

The electronic structure of LiMnO2 and Li2MnO3 was studied by means of X-ray photoelectron and soft X-ray emission spectroscopy. For LiMnO2, LSDA and LSDA+U calculations were carried out. The LSDA+U calculations are in rather good agreement with the measured valence-band structure as well as with the magnetic and electrical properties of LiMnO2. It is shown that the band gap in LiMnO2 is determined by the charge-transfer effect.

The electronic structure of the solid solutions Mg1-xCuxO (x= 0.10,0.12,0.1 5,0.20) with the NaCl structure was studied by means of x-ray photoelectron and soft-x-ray emission spectroscopy (XES). The XES measurements include a study of the fluorescence O K alpha spectra measured at the photon excitation energy of 550 eV and the electron-excited Cu Lcr spectra. Based on the analysis of the valence-band spectra, the partial Cu 3d states and the partial O 2p states in the O 2p-Cu 3d(4sp) bond are separated. The distribution of the partial Cu 3d states in Mg1-xCuxO is similar to that in CuO. The partial O 2p states in the O 2p-Cu 3d(4sp) bond in Mg1-xCuxO correspond essentially to the O 2p states in CuO. That means that the Cu-O interactions practically do not depend on the difference in the crystal structures of Mg1-xCuxO and CuO, but are mainly determined by electronic characteristics of atoms. The exchange splitting in the Cu 3s photoemission spectrum is analyzed. It was established that the degree of covalency and the occupancy of Cu 3d states in Mg1-xCuxO solid solutions are less than those in CuO.

We present metal 3s x-ray photoelectron spectra of different transition metal oxides. The values of the 3s exchange splitting for the 3d metal oxides are given as a function of the 3d electron number in the ground state. The spectra were analysed using the simple two-configuration model of the interatomic configuration mixing. The change of the 3s spectra is ascribed to the change of the charge-transfer energy.

A series of V2-xMoxO5 (x equals 0.2, 0.4, 0.6, 0.8) samples has been investigated by X-ray photoelectron spectroscopy (XPS). MoO3, VO2, V2O5 (powders), VO2(c) and Na0.33V2O5(c) have been used as reference samples. According to the XPS measurements, the valence of Mo atoms in this series is not changed during the Mo doping and it is close to that of MoO3. The V atoms show a mixed valence in the V2-xMoxO5 system: with increasing of the Mo content, a higher concentration of tetravalent V atoms is observed. For one sample of this series, V1.2Mo0.8O5, it was found that the XPS valence band and also the core level spectra are close to those of another mixed- valence system, Na0.33V2O5. Both compounds show similar electrical properties, which can be interpreted in terms of a two-level hopping model. It is concluded that the impurity states in the band gap of both compounds have 3d like character and they are formed at the expense of the additional electrons of Mo or Na.

The results of measurements of X-ray photoelectron (XPS), X-ray emission (XES) and X-ray absorption spectra and LSDA band structure calculations of Pr0.5Sr0.5MnO3 are presented. The excitation energy dependence of Mn L2,3 and O Kα X-ray emission spectra of Pr0.5Sr0.5MnO3 is measured using tunable synchrotron radiation. Comparing XPS and XES measurements and the LSDA band structure calculations, one concludes that the Mn 3d states are localized near the top of the valence band. Some differences in the Mn 3d-distribution in the upper part of the XPS valence band and Mn L3 XES are due to spin selection rules.

The electronic structure of LiCu2O2 was studied using x-ray emission (Cu L-alpha, O K-alpha) and photoelectron spectroscopy (valence band and core levels) as well as band-structure calculations in terms of local spin-density approximation (LSDA) and LSDA + U approaches. According to the x-ray-emission and photoelectron spectra the valence states of the Cu atoms are found to be mixed, i.e., 2+ and 1+. The LSDA calculations are contradictory to the experimental data and cannot reproduce the band gap and magnetic properties of LiCu2O2. The LSDA + U calculations describe the insulator and antiferromagnetic properties much better but the overestimation of the screened Coulomb parameter U leads to a binding-energy shift of the Cu-II 3d states and this distorts the proper modeling of the valence-band structure. The magnetic structure of LiCu2O2 is discussed, taking our LSDA + U band-structure calculations into account. [S0163-1829(98)04108-3].