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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]

We demonstrate a method of x-ray absorption spectroscopy (XAS) that is bulk sensitive, like traditional fluorescence yield measurements, but is not affected by self-absorption or saturation effects. This measure of XAS is achieved by scanning the incident photon energy through an absorption edge and using an energy-sensitive photon detector to measure the partial fluorescence yield (PFY). The x-ray emission from any element or core-hole excitation that is not resonant with the absorption edge under investigation is selected from the PFY. It is found that the inverse of this PFY spectrum, which we term inverse partial fluorescence yield (IPFY), is linearly proportional to the x-ray absorption cross-section without any corrections due to saturation or self-absorption effects. We demonstrate this technique on the Cu L2,3 and Nd M4,5 absorption edges of the high-Tc cuprate La1.475Nd0.4Sr0.125CuO4 by measuring the O Kα PFY and comparing the total electron yield, total fluorescence yield, and IPFY spectra. [ABSTRACT FROM AUTHOR]

We investigated the electronic and magnetic properties of fully oxidized BaFeO3 thin films, which show ferromagnetic-insulating properties with cubic crystal structure, by hard x-ray photoemission spectroscopy (HAXPES), x-ray absorption spectroscopy (XAS), and soft x-ray magnetic circular dichroism (XMCD). We analyzed the results with configuration-interaction (CI) cluster-model calculations for Fe4+, which showed good agreement with the experimental results. We also studied SrFeO3 thin films, which have an Fe4+ ion helical magnetism in cubic crystal structure, but are metallic at all temperatures. We found that BaFeO3 thin films are insulating with large magnetization (1.7 µB/formula unit) under ~1 T, using valence-band HAXPES and Fe 2p XMCD, which is consistent with the previously reported resistivity and magnetization measurements. Although Fe 2p core-level HAXPES and Fe 2p XAS spectra of BaFeO3 and SrFeO3 thin films are quite similar, we compared the insulating BaFeO3 to metallic SrFeO3 thin films with valence-band HAXPES. The CI cluster-model analysis indicates that the ground state of BaFeO3 is dominated by d5L(L: ligand hole) configuration due to the negative charge transfer energy, and that the band gap has significant O 2p character. We revealed that the differences of the electronic and magnetic properties between BaFeO3 and SrFeO3 arise from the differences in their lattice constants, through affecting the strength of hybridization and bandwidth. [ABSTRACT FROM AUTHOR]

The coupled electronic-structural modulations of the ligand states in IrTe2 have been studied by x-ray absorption spectroscopy and resonant elastic x-ray scattering (REXS). Distinctive preedge structures are observed at the Te- M4,5 (3d → 5p) absorption edge, indicating the presence of a Te 5p -h 5d covalent state near the Fermi level. An enhancement of the REXS signal near the Te 3d → 5p resonance at the Q = (1/5,0, - 1 /5) superlattice reflection is observed below the structural transition temperature Ts ∼ 280 K. The analysis of the energy-dependent REXS line shape reveals the key role played by the spatial modulation of the covalent Te 5 p-lr 5d bond density in driving the stripelike order in IrTes, and uncovers its coupling with the charge and/or orbital order at the Ir sites. The similarity between these findings and the charge-ordering phenomenology recently observed in the high-temperature superconducting cuprates suggests that the iridates may harbor similar exotic phases. [ABSTRACT FROM AUTHOR]

We report the detailed electronic structure of a hole-doped delafossite oxide CuCr1-xMgxO2 (0 ⩽ x ⩽ 0.03) studied by photoemission spectroscopy (PES), soft x-ray absorption spectroscopy (XAS), and band-structure calculations within the local-density approximation +U (LDA + U) scheme. Cr/Cu 3p-3d resonant PES reveals that the near-Fermi-level leading structure has primarily the Cr 3d character with a minor contribution from the Cu 3d through Cu 3d-O 2p-Cr 3d hybridization, having good agreement with the band-structure calculations. This indicates that a doped hole will have primarily the Cr 3d character. Cr 2p PES and L-edge XAS spectra exhibit typical Cr3+ features for all x, while the Cu L-edge XAS spectra exhibited a systematic change with x. This indicates now that the Cu valence is monovalent at x = 0 and the doped hole should have Cu 3d character. Nevertheless, we surprisingly observed two types of charge-transfer satellites that should be attributed to Cu+ (3d10) and Cu2+ (3d9) like initial states in Cu 2p-3d resonant PES spectrum of at x = 0, while Cu 2p PES spectra with no doubt shows the Cu+ character even for the lightly doped samples. We propose that these contradictory results can be understood by introducing not only the Cu 4s state, but also finite Cu 3d,4s-Cr 3d charge transfer via 0 2p states in the ground-state electronic configuration. [ABSTRACT FROM AUTHOR]

A correction to an article on X-ray absorption spectroscopy that was published in previous issue of the journal is presented.

Single crystals of SrFe1-xCox0³ solid solution with high valence ions (Fe4+/Co4+) were synthesized by combining floating-zone and high-pressure oxygen-annealing techniques. As the Co content (x) is increased, the ground state changes from the helimagnetic state (x ≤ 0.05) through cluster glass to the ferromagnetic state (x ≥ 0.2), with a high Curie temperature ranging between 245 and 337 K. We found that, within the helimagnetic state (x ≤ 0.05), several different magnetic phases, which possibly reflect versatile three-dimensional helical orders with multiple wave vectors, emerge depending on temperature and magnetic field strength. In addition, we observed Co-concentration-dependent systematic evolution of the complex magnetic phase diagram. Resonant soft x-ray diffraction measurements revealed a gradual decrease in the wave vector of the helix toward the ferromagnetic phase. [ABSTRACT FROM AUTHOR]

Static charge-density-wave (CDW) and spin-density-wave (SDW) order has been convincingly observed in La-based cuprates for some time. However, more recently it has been suggested by quantum oscillation, transport, and thermodynamic measurements that density-wave order is generic to underdoped cuprates and plays a significant role in YBa2Cu3O6+δ (YBCO). We use resonant soft x-ray scattering at the Cu L and O K edges to search for evidence of density-wave order in ortho-II and ortho-VIII oxygen-ordered YBCO. We report a null result—no evidence for static CDW order—in both ortho-II and ortho-VIII ordered YBCO. While this does not rule out static CDW order in the CuO2 planes of YBCO, these measurements place limits on the parameter space (temperature, magnetic field, scattering vector) in which static CDW order may exist. In addition, we present a detailed analysis of the energy and polarization dependence of the ortho-II superstructure Bragg reflection [0.5 0 0] at the Cu L edge. The intensity of this peak, which is due to the valence modulations of Cu in the chain layer, is compared with calculations using atomic scattering form factors deduced from x-ray absorption measurements. The calculated energy and polarization dependence of the scattering intensity is shown to agree very well with the measurement, validating the approach and providing a framework for analyzing future resonant soft x-ray scattering measurements. [ABSTRACT FROM AUTHOR]

In order to understand the influence of strain and film thickness on the electronic structure of thin films of strongly correlated oxides, we have applied hard x-ray photoemission (HXPS) at 6 keV, soft x-ray photoemission (XPS) at 1.5 keV, and transmission electron microscopy to epitaxial LaNiO3 films deposited on two substrates: LaAlO3 (compressive strain) and (LaAlO3)0.3(Sr2AlTaO6)0.7 (tensile strain). Using inelastic attenuation lengths in LaNiO3 determined from the HXPS data, we have decomposed valence-band spectra into layer-specific contributions. This decomposition is validated by comparing with the results of first-principles calculations using a hybrid functional. The resultant thin-film LaNiO3 densities of states exhibit significant differences in spectral weights for the thinnest LaNiO3 films. A gap opening consistent with a metal-to-insulator transition is observed for the thinnest 2.7 nm LaNiO3 film on an (LaAlO3)0.3(Sr2AlTaO6)0.7 substrate, with a similar gap opening also being observed in complementary soft x-ray photoemission at 1.5 keV for a thinner 1.4 nm film on an LaAlO3 substrate. A metal-to-insulator transition in very thin nm-scale films of LaNiO3 is thus suggested as a general phenomenon. [ABSTRACT FROM AUTHOR]

We have studied the electronic structure of multiferroic BiCoO3 using x-ray photoemission spectroscopy (XPS), x-ray absorption spectroscopy (XAS), and subsequent model calculations. The XAS results show that the Co3+ ion takes the high-spin d6 configuration which usually prefers G-type antiferromagnetic state. The XPS results and model Hartree-Fock calculations show that, in case of BiCoO3, small charge-transfer energy plays an essential role to enhance the Co—O—O—Co superexchange pathways. It is found that the combination of ferro-type orbital ordering of Co 3d t2g and the Co—O—O—Co superexchange interaction gives rise to C-type antiferromagnetic state in BiCoO3. The present analysis suggests that, in addition to the Bi-O bonds responsible for the noncentrosymmetric deformation, the O—O bonds are important to stabilize the multiferroic phase of BiCoO3. [ABSTRACT FROM AUTHOR]

We report an x-ray photoemission spectroscopy (XPS) and x-ray absorption spectroscopy (XAS) study on K2V8-xTixO16 (x?=?0.0, 0.3, and 4.0) in which the metal-insulator transition (MIT) and the tetragonal-to-monoclinic structural transition show different responses against the Ti doping. The spectral change of V 2p XAS across the MIT is similar to that observed in VO2, indicating that the V-V pairing is responsible for the MIT. In the insulating phase, the V 2p XPS spectra are split into the V3+ and V4+ features showing the localized character of the V 3d electrons. In addition, the V 2p XAS spectra of the monoclinic insulating phase suggest that the V-V pairing is weakened, and, instead, the V3+-V4+ coupling is strengthened by orbital ordering. In contrast to VO2, the existence of the V3+ component in K2V8-xTixO16 gives additional orbital instability in the insulating phase, which competes with the V-V pairing. [ABSTRACT FROM AUTHOR]