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We have studied the electronic structure of Li1+x[Mn0.5Ni0.5]1-xO2(x=0.00 and 0.05), one of the promising cathode materials for Li ion battery, by means of x-ray photoemission and absorption spectroscopy. The results show that the valences of Mn and Ni are basically 4+ and 2+, respectively. However, the Mn3+ component in the x=0.00 sample gradually increases with the bulk sensitivity of the experiment, indicating that the Jahn-Teller active Mn3+ ions are introduced in the bulk due to the site exchange between Li and Ni. The Mn3+ component gets negligibly small in the x=0.05 sample, which indicates that the excess Li suppresses the site exchange and removes the Jahn-Teller active Mn3+. [ABSTRACT FROM AUTHOR]

We investigate the electronic structure of a perovskite-type Pauli paramagnet SrMoO3 (t2g2) thin film using hard x-ray photoemission spectroscopy and compare the results to realistic calculations that combine density functional theory within the local-density approximation (LDA) with dynamical mean-field theory (DMFT). Despite the clear signature of electron correlations in the electronic specific heat, the narrowing of the quasiparticle bands is not observed in the photoemission spectrum. This is explained in terms of the characteristic effect of Hund's rule coupling for partially filled t2g bands, which induces strong quasiparticle renormalization already for values of Hubbard interaction which are smaller than the bandwidth. This interpretation is supported by DMFT model calculations including Hund's rule coupling, which show a renormalization of low-energy quasiparticles without affecting the overall bandwidth. The photoemission spectra show additional spectral weight around -2.5 eV that is not present in the LDA+DMFT results, pointing to a source of correlations that is not present in our calculations that include only on-site interactions. We interpret this weight as a plasmon satellite, which is supported by the measured core-level spectra that all show satellites at this energy. [ABSTRACT FROM AUTHOR]

We have investigated the electronic and magnetic properties of Co-doped Pr0.8Ca0.2MnO3 thin films using various spectroscopic techniques. X-ray absorption and hard x-ray photoemission spectroscopy revealed that the substituted Co ions are in the divalent state, resulting in hole doping on the Mn atoms. Studies of element-selective magnetic properties by x-ray magnetic circular dichroism found a large orbital magnetic moment for the Co ions. These spectroscopic studies reveal that the substituted Co ions play several roles of hole doping for Mn, ferromagnetic superexchange coupling between the Co2+ and Mn4+ ions, and orbital magnetism of the Co2+ ions. Competition among these complex interactions produces the unique electronic and magnetic behaviors including enhanced coercivity of the Co-doped Pr0.8Ca0.2MnO3. [ABSTRACT FROM AUTHOR]

We report normal and superconducting properties of the Rashba-type noncentrosymmetric compound CaIrSÍ3 using single crystalline samples with nearly 100% superconducting volume fraction. The electronic density of states revealed by the hard x-ray photoemission spectroscopy can be well explained by the relativistic first-principles band calculation. This indicates that strong spin-orbit interaction indeed affects the electronic states of this compound. The obtained H-T phase diagram exhibits only approximately 10% anisotropy, indicating that the superconducting properties are almost three dimensional. Nevertheless, strongly anisotropic vortex pinning is observed. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated the magnetic ordering in an orthorhombic YMnO3 thin film using resonant soft x-ray and hard x-ray diffraction. Results show that a temperature-dependent incommensurate magnetic reflection below 45 K and a commensurate lattice-distortion reflection below 35 K. It was also found that the ground state is composed of coexisting E-type and cycloidal states.

Abstract: We have performed in situ photoemission and O 1s X-ray absorption studies of La1−xSrxFeO3 () epitaxial thin films grown by laser molecular beam epitaxy. We found that hole doping induces spectral weight transfer from below the Fermi level to above it across the gap in a highly non-rigid-band-like manner. We also observed the temperature dependence on the spectra of the sample, which shows a charge disproportionation at 190 K. With decreasing temperature, we observed gradual changes of the spectra with spectral weight transfer primarily within the eg band. [Copyright &y& Elsevier]

Abstract: We have performed an in situ angle-resolved photoemission study of atomically flat surfaces of La1− x Sr x MnO3 (LSMO) single-crystal thin films grown on SrTiO3 (001) substrates by laser molecular beam epitaxy, and investigated the changes in the band structure induced by hole-doping. The band structures of LSMO x =0.4 thin films consist of several highly dispersive O 2p-derived bands at the binding energies of 2.5–7eV, almost dispersionless Mn 3d t 2g bands at ∼2eV, and a dispersive Mn 3d e g -derived majority band at ∼0.5eV. We find that the energy positions of these bands monotonically shift toward higher binding energy with decreasing hole concentration in a rigid-band manner, whereas the lower binding energy part of the e g -derived emission within 1.5eV of the Fermi level (E F) gradually disappears. These results suggest that the simple rigid-band model does not describe the electronic structure near E F of LSMO. [Copyright &y& Elsevier]

Eu doped rare-earth orthovanadates are known to be good red phosphor materials. In particular, LaVO4:Eu is a promising candidate due to the low Eu-site point symmetry, and thus high dipole transition probability within Judd-Ofelt theory. However, the low solubility limit (<3 mol %) of Eu in LaVO4 prevents its efficient use as a phosphor. We present optical evidence of enhanced Eu solubility as high as 10 mol % in LaVO4:Eu thin films grown by pulsed laser deposition and postannealing. The photoluminescent intensity exceeded that of YVO4:Eu thin films when excited below the host bandgap, indicating stronger direct emission of Eu in LaVO4. [ABSTRACT FROM AUTHOR]

We present an x-ray absorption study of the oxidation states of transition-metal-ions of LiMnO2 and its related materials, widely used as cathodes in Li-ion batteries. The comparison between the obtained spectrum and the configuration-interaction cluster-model calculations showed that the Mn3+ in LiMnO2 is a mixture of the high-spin and low-spin states. We found that Li deficiencies occur in the case of Cr substitution, whereas there are no Li deficiencies in the case of Ni substitution. We conclude that the substitution of charge-transfer-type Ni or Cu is effective for LiMnO2 battery materials. [ABSTRACT FROM AUTHOR]

Epitaxial Ba0.5Sr0.5TiO3 thin films were prepared on Nb-doped SrTiO3 (100) substrates by the pulsed laser deposition technique and were studied by measuring the Ti 2p→3d resonant photoemission spectra in the valence-band region as a function of film thickness, both at room temperature and low temperature. The results demonstrated an abrupt variation in the spectral structures between 2.8 nm (∼7 ML) and 2.0 nm (∼5 ML) Ba0.5Sr0.5TiO3 films, suggesting that there exists a critical thickness for phase change in the range of 2.0–2.8 nm. This may be ascribed mainly to the intrinsic size effects. [ABSTRACT FROM AUTHOR]

Abstract: We have performed an in situ angle-resolved photoemission spectroscopy (ARPES) on single-crystal surfaces of (LSMO) thin films to investigate the electronic structure near the Fermi level (). ARPES spectra near reveal the existence of a dispersive Mn-3d derived conduction band indicative of an electron pocket centered at the point. Comparing the experimental band structure with the local density approximation + band-structure calculation, the estimated size of the Fermi surface is consistent with the prediction of the calculation, while the measured bandwidth is significantly narrower than the calculation. The discrepancy between the two suggests that the renormalization effect is significant due to the strong electron correlation in LSMO. [Copyright &y& Elsevier]

Abstract: We have performed an in situ photoemission study of thin films grown on (001) by laser molecular beam epitaxy. By utilizing Mn resonant photoemission, we obtained the Mn 3d partial density of states. There was no density of states at the Fermi level, consistent with the insulating behavior of this material. Chemical potential pinning, which was observed in bulk samples, was not observed in the present study, consistent with the suppression of charge ordering under the compressive strain from the substrate. [Copyright &y& Elsevier]

We used x-ray photoemission spectroscopy to investigate the electronic structure of one to five unit cell thick layers of the Mott insulator LaVO3 embedded in LaAlO3. By limiting the upper layer of LaAlO3 to three unit cells, the underlying LaVO3 could be probed. The V 2p core-level spectra had both V3+ and V4+ components, and above two unit cell thick LaVO3, the structures exhibited spectra similar to bulk samples. The atomically flat surfaces enabled the study of the emission angle dependence, which indicates that the V4+ is localized to the topmost layer. These results demonstrate the potential for probing interface electronic structure in oxide ultrathin films by surface spectroscopy. [ABSTRACT FROM AUTHOR]

We have investigated the interfacial electronic structure of La0.6Sr0.4MnO3 (LSMO)/SrTiO3 (STO)/LSMO heterojunctions utilizing the elemental selectivity of photoemission spectroscopy. The Ti 2p core-level spectra clearly show Ti4+ states and do not exhibit any indication of Ti3+ states in TiO2 layers irrespective of a different kind of adjacent atomic layer with different chemical carrier concentration. This result indicates that the Ti ions in the TiO2 atomic layers preserve their tetravalent states even in the vicinity of the valence-mismatched interface between LSMO and STO, reflecting the chemical stability of the Ti4+ states. [ABSTRACT FROM AUTHOR]