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Through a high-precision soft x-ray magnetic circular dichroism (XMCD) study of the intermediate-valence compound $\mathrm{Sm}{\mathrm{Os}}_{4}{\mathrm{Sb}}_{12}$, we show our successful approach of revealing unprecedented details of Kondo screening below a characteristic temperature of ${T}_{0}\ensuremath{\sim}20$ K in the paramagnetic phase. The multiplet XMCD structure at the Sm ${M}_{5}$ edge sensitive to the $4f$ configuration enabled us to observe a clear difference between the temperature evolution above and below ${T}_{0}$ with one- and two-component behavior, respectively. Our findings are in strong contrast to the conventional Kondo crossover that coincides with the valence transition, but are qualitatively accounted for by theoretical XMCD predictions combined with the two-fluid phenomenology recently proposed. This work contributes to the large context of Kondo physics that is closely related to quantum criticality in heavy fermion systems.

We investigate the ground-state properies of the $K-\Gamma$ model on a honeycomb lattice using series expansions and numerical exact diagonalizations, where the model includes Kitaev ($K$) and symmetric off-diagonal ($\Gamma$) interactions. Starting from the weakly interacting dimers on the specific bond, we strengthen the interdimer interactions to the isotropically interacting system. We show that depending on $\Gamma$ and $K$, the dimer state survives up to the isotropically interacting system, where the phase transition occurs, or obeys a phase transition to a magnetically ordered state at an anisotropic interaction. The results are summarized in the phase diagram. We also show that the Kekul\'{e} dimerized state is unstable in the isotropic $K-\Gamma$ model., Comment: 7 pages, 7 figures, revised version

Detailed information on the electronic states of both V and Mn $3d$ electrons in the ferrimagnet $\mathrm{M}{\mathrm{n}}_{2}\mathrm{VAl}$ is obtained by bulk sensitive resonant inelastic soft x-ray scattering (SX-RIXS) excited with circularly polarized light under an external magnetic field. The results under the V $L$-edge excitation have revealed the negligible partial density of states (PDOS) of the V $3d$ states around the Fermi energy as well as their rather localized character. Under the Mn $L$-edge excitation, on the other hand, the spectra are dominated by fluorescence with clear magnetic circular dichroism with noticeable excitation photon energy dependence. Compared with the theoretical prediction of the RIXS spectra based on the density-functional-theory band structure calculation, an itinerant, spin-dependent character of the Mn $3d$ states and decays of the Mn $2p$ core states are confirmed in consistence with the half-metallicity of the Mn $3d$ states.

We apply the infinite time-evolving-block-decimation algorithm to calculate the dynamical spin-structure factors of the quasi-one-dimensional (q1D) S=1 antiferromagnetic spin system with the single-ion anisotropy and the bond alternation. We find that excitation continuum originating from magnons is quantized, when the staggered field induced by the weak inter-chain interaction is taken into account. The excitation energies of the quantized excitation spectra are well explained by negative zeros of the Airy functions, when the easy-axis anisotropy is strong and the ground state is located deep in the N\'eel phase. This quantization of the magnon continuum is a counterpart of the spinon confinement, which has been recently discussed in q1D S=1/2 antiferromagnets. We further show that, when the staggered field exists, the quantized excitation spectra appear the phase boundary between the Haldane phase and the N\'eel phase of the phase diagram without the staggered field. However, the quantized excitation spectra disappear in the singlet dimer phase., Comment: 8 pages, 5 figures

We use an exact numerical diagonalization method to calculate the dynamical spin structure factors of three ab initio models and one ab initio guided model for a honeycomb-lattice magnet $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$. We also use thermal pure quantum states to calculate the temperature dependence of the heat capacity, the nearest-neighbor spin-spin correlation function, and the static spin structure factor. From the results obtained from these four effective models, we find that, even when the magnetic order is stabilized at low temperature, the intensity at the $\mathrm{\ensuremath{\Gamma}}$ point in the dynamical spin structure factors increases with increasing nearest-neighbor spin correlation. In addition, we find that the four models fail to explain heat-capacity measurements whereas two of the four models succeed in explaining inelastic-neutron-scattering experiments. In the four models, when temperature decreases, the heat capacity shows a prominent peak at a high temperature where the nearest-neighbor spin-spin correlation function increases. However, the peak temperature in heat capacity is too low in comparison with that observed experimentally. To address these discrepancies, we propose an effective model that includes strong ferromagnetic Kitaev coupling, and we show that this model quantitatively reproduces both inelastic-neutron-scattering experiments and heat-capacity measurements. To further examine the adequacy of the proposed model, we calculate the field dependence of the polarized terahertz spectra, which reproduces the experimental results: the spin-gapped excitation survives up to an onset field where the magnetic order disappears and the response in the high-field region is almost linear. Based on these numerical results, we argue that the low-energy magnetic excitation in $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$ is mainly characterized by interactions such as off-diagonal interactions and weak Heisenberg interactions between nearest-neighbor pairs, rather than by the strong Kitaev interactions.

We have studied the electronic structure of ferrimagnetic ${\mathrm{Mn}}_{2}\mathrm{VAl}$ single crystals by means of soft x-ray absorption spectroscopy (XAS), x-ray absorption magnetic circular dichroism (XMCD), and resonant soft x-ray inelastic scattering (RIXS). We have successfully observed the XMCD signals for all the constituent elements. The Mn ${L}_{2,3}$ XAS and XMCD spectra are reproduced by spectral simulations based on density-functional theory, indicating the itinerant character of the Mn $3d$ states. On the other hand, the V $3d$ electrons are rather localized since the ionic model can qualitatively explain the V ${L}_{2,3}$ XAS and XMCD spectra. This picture is consistent with local $dd$ excitations revealed by the V ${L}_{3}$ RIXS.

We present a detailed study of the Ti $3d$ carriers at the interface of ${\mathrm{LaAlO}}_{3}/{\mathrm{SrTiO}}_{3}$ heterostructures by high-resolution resonant inelastic soft x-ray scattering (RIXS), with special focus on the roles of overlayer thickness and oxygen vacancies. Our measurements show the existence of interfacial Ti $3d$ electrons already below the critical thickness for conductivity. The (total) interface charge carrier density increases up to a ${\mathrm{LaAlO}}_{3}$ overlayer thickness of 6 unit cells before it levels out. Furthermore, we observe strong Ti $3d$ charge carrier doping by oxygen vacancies. The RIXS data combined with photoelectron spectroscopy and transport measurements indicate the simultaneous presence of localized and itinerant charge carriers. At variance with previous interpretations, we show that in our excitation energy dependent RIXS measurements the amounts of localized and itinerant Ti $3d$ electrons in the ground state do not scale with the intensities of the Raman and fluorescence peaks, respectively. Rather, we attribute the observation of either Raman components or fluorescence signal to the specific nature of the intermediate state reached in the RIXS excitation process.

Fe ${L}_{2,3}$-edge x-ray absorption spectra (XAS) and magnetic circular dichroism (MCD) in resonant inelastic x-ray scattering (RIXS) of $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ were measured to identify the electronic structure responsible for its weak ferromagnetism caused by the Dzyaloshinskii-Moriya interaction (DMI) at room temperature. In contrast to negligible MCD in XAS, MCD in RIXS (RIXS-MCD) was clearly observed in the $dd$ excitation at 1.8 eV via excitation to charge-transfer states. Furthermore, RIXS-MCD showed a crystal orientation dependence, indicating that the observed RIXS-MCD originated from DMI. The observed RIXS-MCD is well described by ab initio charge-transfer multiplet calculations, revealing that the RIXS-MCD derives from spin flip excitations at delocalized ${e}_{\mathrm{g}}$ orbitals. By the combination of the experiments and calculations, RIXS-MCD has unraveled that the origin of DMI in $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ is the ${e}_{\mathrm{g}}$ orbitals, which are strongly hybridized with the $2p$ orbitals of oxygen atoms. The results demonstrate the importance of RIXS-MCD for identifying the electronic structure related to DMI.

Contrary to the original expectation, ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$ is not a Kitaev's quantum spin liquid (QSL) but shows a zigzag-type antiferromagnetic order in experiments. Here, we propose experimental clues and criteria to measure how a material in hand is close to the Kitaev's QSL state. For this purpose, we systematically study thermal and spin excitations of a generalized Kitaev-Heisenberg model studied by Chaloupka et al., Phys. Rev. Lett. 110, 097204 (2013) and an effective ab initio Hamiltonian for ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$ proposed by Yamaji et al., Phys. Rev. Lett. 113, 107201 (2014), by employing a numerical diagonalization method. We reveal that closeness to the Kitaev's QSL is characterized by the following properties, besides trivial criteria such as reduction of magnetic ordered moments and N\'eel temperatures. (1) Two peaks in the temperature dependence of specific heat at ${T}_{\ensuremath{\ell}}$ and ${T}_{h}$ caused by the fractionalization of spin to two types of Majorana fermions. (2) In between the double peak, a prominent plateau or shoulder pinned at $\frac{R}{2}ln2$ in the temperature dependence of entropy, where $R$ is the gas constant. (3) Failure of the linear spin wave approximation at the low-lying excitations of dynamical structure factors. (4) Small ratio ${T}_{\ensuremath{\ell}}/{T}_{h}$ close to or less than 0.03. According to the proposed criteria, ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$ is categorized to a compound close to the Kitaev's QSL, and is proven to be a promising candidate for the realization of the QSL if the relevant material parameters can further be tuned by making thin film of ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$ on various substrates or applying axial pressure perpendicular to the honeycomb networks of iridium ions. Applications of these characterization to ${({\mathrm{Na}}_{1\ensuremath{-}x}{\mathrm{Li}}_{x})}_{2}{\mathrm{IrO}}_{3}$ and other related materials are also discussed.

We investigated $\mathrm{SrFe}{}_{2}(\mathrm{As}{}_{1\ensuremath{-}x}{\mathrm{P}}_{x}){}_{2}$ single crystals with four different phosphorus concentrations $x$ in the superconducting phase $(x=0.35,0.46)$ and in the magnetic phase $(x=0,0.2)$. The superconducting samples display a V-shaped superconducting gap, which suggests nodal superconductivity. Furthermore, we determined the superconducting coherence length by measuring the spatially resolved superconducting density of states. Using inelastic tunneling spectroscopy, we investigated excitations in the samples with four different phosphorus concentrations. Inelastic peaks are related to bosonic modes. The phonon and nonphonon mechanisms for the origin of these peaks are discussed.

金沢大学先端科学・社会共創推進機構, We have studied the electronic structure of ferrimagnetic Mn2VAl single crystals by means of soft x-ray absorption spectroscopy (XAS), x-ray absorption magnetic circular dichroism (XMCD), and resonant soft x-ray inelastic scattering (RIXS). We have successfully observed the XMCD signals for all the constituent elements. The Mn L2,3 XAS and XMCD spectra are reproduced by spectral simulations based on density-functional theory, indicating the itinerant character of the Mn 3d states. On the other hand, the V 3d electrons are rather localized since the ionic model can qualitatively explain the V L2,3 XAS and XMCD spectra. This picture is consistent with local dd excitations revealed by the V L3 RIXS. © 2018 American Physical Society.

We studied magnetism and morphology of metastable bcc Co nanostructures on Au(001) by x-ray magnetic circular dichroism in combination with scanning tunneling microscopy and photoelectron emission microscopy. While room-temperature deposition of Co onto Au(001) leads to the formation of bcc Co thin films with pure in-plane magnetization, postannealing of these thin films at 500 K drastically changes the morphology to bcc Co islands embedded in Au. In accordance with this morphological change, we find that an out-of-plane magnetization emerges additionally and the coexistence of in-plane and out-of-plane remanent magnetizations is observed for the islands. The nanostructure-size dependence of magnetic moments suggests that the magnetization easy axis of the island changes from the in-plane to the out-of-plane direction with decreasing nanostructure size. Such a spin reorientation transition is likely due to the increased fractional population of rim atoms generating the out-of-plane magnetization in the smaller islands. The observed out-of-plane remanent magnetization of the smaller islands indicates their large magnetic anisotropy.

The spin reorientation transition in fcc Co/Ni/Cu(001) epitaxial ultrathin films as a function of Co and Ni film thickness is studied by the combination of photoelectron emission microscopy and x-ray magnetic-circular-dichroism spectroscopy at the Ni ${L}_{2,3}$ edge. This microspectroscopic technique allows one to extract local quantitative information about the Ni magnetic properties on a submicrometer scale. Domain images in the thickness range of 1.4--2.6 atomic monolayers (ML) Co and 11--14 ML Ni show that the spin reorientation occurs as a function of both Co and Ni thicknesses. Increasing the Co thickness or decreasing the Ni thickness leads to a switching of the magnetic easy axis from $[001]$ out-of-plane to $〈110〉$ in-plane directions. A constant effective Ni spin moment similar to the bulk magnetic moment is observed. The Ni orbital to spin moment ratio shows distinctly different values for out-of-plane magnetization $(0.080\ifmmode\pm\else\textpm\fi{}0.005)$ and in-plane magnetization $(0.053\ifmmode\pm\else\textpm\fi{}0.005).$ This is discussed in terms of the connection to the Ni magnetocrystalline anisotropy. The domain density of the perpendicular magnetization increases towards the spin reorientation transition line.

Resonant photoemission (RPES) at the Ce $3\stackrel{\ensuremath{\rightarrow}}{d}4f$ threshold has been performed for $\ensuremath{\alpha}\ensuremath{-}\mathrm{like}$ compound ${\mathrm{CeNi}}_{2}$ with extremely high energy resolution (full width at half maximum 0.2 eV) to obtain bulk-sensitive $4f$ spectral weight. The on-resonance spectrum shows a sharp resolution-limited peak near the Fermi energy which can be assigned to the tail of the Kondo resonance. However, the spin-orbit side band around 0.3 eV binding energy corresponding to the ${f}_{7/2}$ peak is washed out, in constrast to the RPES spectrum at the Ce $4\stackrel{\ensuremath{\rightarrow}}{d}4f$ threshold. This is interpreted as due to the different surface sensitivity, and the bulk-sensitive Ce $3\stackrel{\ensuremath{\rightarrow}}{d}4f$ RPES spectra are found to be consistent with other electron spectroscopy and low energy properties for \ensuremath{\alpha}-like Ce-transition metal compounds, thus resolving controversy on the interpretation of Ce compound photoemission. The $4f$ spectral weight over the whole valence band can also be fitted fairly well with the Gunnarsson-Sch\"onhammer calculation of the single impurity Anderson model, but the detailed features show some dependence on the hybridization band shape and the Ce $5d$ resonant emission.

We have performed Ce $3d\ensuremath{-}4f$ resonance photoemission spectroscopy (RPES) for CePdAs and CePdSb and compared the results with those of Ce $4d\ensuremath{-}4f$ RPES. The $3d\ensuremath{-}4f$ RPES spectra are remarkably different from the $4d\ensuremath{-}4f$ RPES spectra, showing the smaller contribution of the surface electronic structures in the $3d\ensuremath{-}4f$ RPES. On the other hand, the $3d\ensuremath{-}4f$ and $4d\ensuremath{-}4f$ resonance-minimum spectra for CePdSb are well described by the band-structure calculations for LaPdSb by taking the photoionization cross sections into account. This indicates that the surface effect is negligible in the resonance-minimum spectra. The theoretical calculation based on the single-impurity Anderson model well reproduces the surface- and bulk-sensitive Ce $4f$ spectra of both compounds, revealing that the difference between the surface and bulk electronic states originates mainly from the surface core-level shift of the bare $4f$ level. The spectral difference between the two compounds is explained by the different energy dependence of the hybridization strength.

Resonance behaviors of the Ni and Fe $3d,$ $3p$ and $3s$ related satellite photoemission and Auger features are measured for the Ni and Fe $2p$ core excitation in ${\mathrm{NiS}}_{2}$ and ${\mathrm{FeS}}_{2}.$ Chronological interpretation is proposed to the Ni and Fe $2p3p3d$ Auger features. A resonance satellite around the binding energy of 30 eV is identified as due to the plasmon satellite associated with the resonance-enhanced satellite of the $3d$ state.

Angle-resolved photoemission spectra have been measured to study the electronic structures of Ni intercalated layered compound ${\mathrm{Ni}}_{1/3}{\mathrm{TiS}}_{2}.$ The results have shown that some new bands appear in ${\mathrm{Ni}}_{1/3}{\mathrm{TiS}}_{2}$ and the dispersions of most other bands are strongly modified compared with ${\mathrm{TiS}}_{2}.$ It is clarified that the new band near the Fermi level ${(E}_{F})$ is the split-off state or the bonding state between the final states originating from the $|{d}^{1}{(t}_{2g})〉$ and $|{d}^{2}{(t}_{2g}{,e}_{g})L〉$ initial states, where $L$ stands for the $\mathrm{S}3p$ hole state. Another new band observed at \ensuremath{\sim}1 eV below ${E}_{F}$ is hardly dispersive and attributed to the $\mathrm{Ni}{3d}_{{z}^{2}}\ensuremath{-}\mathrm{Ti}{3d}_{{z}^{2}}$ bonding state. The $\mathrm{Ni}3d``{e}_{g}''\ensuremath{-}\mathrm{S}3p$ bonding states are observed in the larger binding energy region. Knowledge of hybridizations among the $3d$ states of the intercalant, $\mathrm{Ti}3d$ states, and $\mathrm{S}3p$ states are essential to interpret the physical properties of ${\mathrm{Ni}}_{1/3}{\mathrm{TiS}}_{2}.$

Electronic structures of the charge-ordering manganite ${\mathrm{Nd}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}(x\ensuremath{\sim}0.5)$ have been studied by resonant and high-resolution photoemission. The Mn $2p$ (Nd $3d)$ resonant photoemission confirmed the Mn $3d$ (Nd $4f)$ states hybridized with the O $2p$ states. The high-resolution Mn $3p$ resonance spectra show a clear transition from the metal to the charge-ordered insulator for $x=0.5$ upon cooling while a Fermi cutoff is seen for $x=0.47$ at all temperatures, suggesting that the transition is induced by a subtle competition between the charge-ordering instability and the double-exchange interaction. Temperature and filling dependence of the spectra implies that the electronic states change not gradually but suddenly at the phase boundary.

The critical properties of the $S=1/2$ Heisenberg two-leg ladders are investigated in a magnetic field. Combining the exact diagonalization method and the finite-size-scaling analysis based on conformal field theory, we calculate the critical exponents of spin correlation functions numerically. For a strong interchain coupling, magnetization dependence of the critical exponents shows characteristic behavior depending on the sign of the interchain coupling. We also calculate the critical exponents for the $S=1/2$ Heisenberg two-leg ladder with a diagonal interaction, which is thought of as a model Hamiltonian of the organic spin ladder compound ${\mathrm{Cu}}_{2}(1,4\ensuremath{-}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{z}\mathrm{a}\mathrm{c}\mathrm{y}\mathrm{c}\mathrm{l}\mathrm{o}\mathrm{h}\mathrm{e}\mathrm{p}\mathrm{t}\mathrm{a}\mathrm{n}\mathrm{e}{)}_{2}{\mathrm{Cl}}_{4}.$ Numerical results are compared with experimental results of temperature dependence of the NMR relaxation rate ${1/T}_{1}.$

The magnetism-induced symmetry breaking in photoelectron diffraction patterns of $2{p}_{3∕2}$ photoelectrons from a ferromagnetic Fe(001) single crystal surface is studied experimentally and theoretically. Two-dimensional photoelectron intensity angular distribution patterns were recorded at 1193 eV photon energy for both helicities of the circularly polarized light and for opposite magnetization directions of the sample by a display-type spherical mirror analyzer, which allows simultaneous energy and momentum analysis of emitted photoelectrons. The macroscopic magnetization of the sample induces an additional symmetry breaking in the circular dichroism of the $\mathrm{Fe}\phantom{\rule{0.3em}{0ex}}2{p}_{3∕2}$ photoelectron angular distribution patterns which is related to the presence of magnetic moments on the Fe atoms. Multiple-scattering cluster photoelectron diffraction calculations agree well with experiment, and reproduce even fine details of the observed photoelectron diffraction features. The details of that breaking of mirror symmetry of photoelectron scattering in the plane spanned by light incidence and electron emission due to the presence of a magnetization within that plane depends both on the structure and the magnetism of the sample. In connection with multiple scattering calculations, measurements of the magnetism-induced symmetry breaking by two-dimensional photoelectron diffraction patterns may thus be used as a powerful tool for simultaneous structural and magnetic investigations of single crystalline magnetic samples and ultrathin films.

We have studied the electronic structure of NiS 2−x Se x , which undergoes a metal-insulator transition as functions of composition x and temperature, by means of photoemission and inverse-photoemission spectroscopy. Spectral changes across the transition near the Fermi level (E F ) (particularly within ~100meV of E F ) have been interpreted as due to a "semimetallic" closure of the band gap in going from the insulating phase to the antiferromagnetic metallic phase. On the other hand, there is also composition- and temperature-dependent spectral weight transfer over a wider energy range of ~0.5-1eV, indicating significant correlation effects. Photoemission intensity just below E F remains high in the insulating phases, indicating that the carrier number is large at high temperatures and that the activation-type transport is due to the activated mobility rather than the activated carrier number.

We have studied the effect of Lu substitution on the Kondo insulator YbB 12 by high-resolution photoemission. Comparison of the spectra of YbB 12 ,Y b 0.5Lu 0.5B 12 , and LuB 12 reveals that the density of states ~DOS! of the B sp -derived conduction band near the Fermi level is reduced in YbB 12 over a rather wide (; 40 meV! energy region. Lu substitution ~i! recovers the reduced B sp DOS, ~ii! shifts the Yb 4 f -derived Kondo peak towards higher binding energy, and ~iii! decreases the Yb valence. These results are consistently analyzed using the Anderson-impurity model, and imply interaction between the Yb 4 f ions mediated by the Yb 4 f -B sp hybridization in YbB 12 . @S0163-1829~97!03846-0#

We have made a high-resolution photoemission study of quasi-two-dimensional organic conductors BEDT-TTF salts which have various ground states, namely, antiferromagnetic insulator {kappa}-(ET-d{sub 8}){sub 2}Cu[N(CN){sub 2}]Clthinsp, paramagnetic metal {alpha}-(ET){sub 2}KHg(SCN){sub 4}, and superconductors {kappa}-(ET){sub 2}Cu(NCS){sub 2} and {kappa} -(ET){sub 2}Cu[N(CN){sub 2}]Br, where ET denotes BEDT-TTF or bisethylenedithio-tetrathiafulvalene. In all the spectra, the photoemission intensity is suppressed near the Fermi level (E{sub F}), especially for the {kappa}-phase salts, although we have clearly observed a finite E{sub F} intensity for {alpha}-(ET){sub 2}KHg(SCN){sub 4}. Hartree-Fock band-structure calculations for the paramagnetic metallic and antiferromagnetic insulating states qualitatively explain the spectra of {alpha}-(ET){sub 2}KHg(SCN){sub 4} and {kappa}-(ET-d{sub 8}){sub 2}Cu[N(CN){sub 2}]Cl, respectively, while those of {kappa}-(ET){sub 2}Cu(NCS){sub 2} and {kappa}-(ET){sub 2}Cu[N(CN){sub 2}]Br strongly deviate from the calculations for the corresponding ground states. These observations imply that, among the metallic compounds, electrons are more strongly correlated in the {kappa}-phase salts than in {alpha}-(ET){sub 2}KHg(SCN){sub 4}. It is shown that long-range electron correlation is quite important to explain the strong deviation of the spectra from the band-structure calculation. The spectra of the {kappa}-phase salts exhibit a remarkable similarity between the metallic (superconducting) and insulating phases across the chemical pressure-induced phase transition. We have also observed unusual temperature dependence ofmore » the spectra for {kappa}-(ET){sub 2}Cu(NCS){sub 2}, {alpha}-(ET){sub 2}KHg(SCN){sub 4}, and {kappa}-(ET-d{sub 8}){sub 2}Cu[N(CN){sub 2}]Cl. {copyright} {ital 1997} {ital The American Physical Society}« less

Two-dimensional angular distribution patterns of photoemission are calculated on the band picture for $1T\ensuremath{-}{\mathrm{TaS}}_{2}$ for the normal incidence excitation by linearly and circularly polarized lights. The calculated results for the linearly polarized lights with $x$ and $y$ polarization perpendicular to the crystal $c$ axis ($z$ axis) can explain the experimental results of the linear dichroism obtained by the two-dimensional hemispherical mirror analyzer. The behavior of the calculated circular dichroism is discussed.

We report the core photoabsorption (XAS) and magnetic circular dichroism (MCD) spectra in the Pt ${\mathrm{N}}_{6,7}$ (4f\ensuremath{\rightarrow}5d) region of the ferromagnetic ${\mathrm{CoPt}}_{3}$ . The measured XAS spectra have shown typical Fano line shapes, and the MCD spectrum has shown very unusual features that cannot be explained within the framework of the conventional selection rule for the dipole transition. It is revealed from a theoretical analysis that the strong Fano effect is essential to interpret these MCD features. We will discuss in detail the influence of the Fano effect on the Pt ${\mathrm{N}}_{6,7}$ MCD line shape.

Bulk-sensitive hard x-ray photoemission spectroscopy (HAXPES) reveals for as-grown epitaxial films of half-metallic ferromagnetic CrO2(100) a pronounced screening feature in the Cr 2p3/2 core level and an asymmetry in the O 1s core level. This gives evidence of a finite, metal-type Fermi edge, which is surprisingly not observed in HAXPES. A spectral weight shift in HAXPES away from the Fermi energy is attributed to single-ion recoil effects due to high energy photoelectrons. In conjunction with inverse PES the intrinsic correlated Mott-Hubbard-type electronic structure is unravelled, yielding an averaged Coulomb correlation energy Uav ~ 3.2 eV., Comment: Manuscript 12 pages, 4 figures; Supplemental material 7 pages, 5 figures

The electronic structure of pyrite-type ${\mathrm{NiS}}_{2}$, ${\mathrm{CoS}}_{2}$, and ${\mathrm{FeS}}_{2}$ has been studied by photoemission spectroscopy. From resonant photoemission studies and configuration-interaction cluster-model analysis of the spectra, ${\mathrm{NiS}}_{2}$ is found to be a charge-transfer-type insulator, the band gap of which is formed between the occupied S 3p and the empty Ni 3d states. Cluster-model calculations indicate that the short Fe-S distance favors the low-spin (S=0) ground state in ${\mathrm{FeS}}_{2}$ compared to the high-spin FeS. Resonant photoemission results indicate a sign of electron correlation in the nonmagnetic semiconductor ${\mathrm{FeS}}_{2}$. \textcopyright{} 1996 The American Physical Society.

The electronic structures of ${\mathrm{U}}_{3}$${\mathrm{P}}_{4}$ and ${\mathrm{U}}_{3}$${\mathrm{As}}_{4}$ single crystals are probed by x-ray and vacuum ultraviolet photoemission spectroscopy (XPS and UPS) as well as by x-ray bremsstrahlung isochromat spectroscopy (BIS). The BIS spectra show a broad peak at \ensuremath{\sim}1.8 eV above the Fermi level (${\mathit{E}}_{\mathit{F}}$) with a noticeable tail. Its energy separation of \ensuremath{\sim}2.5 eV from the U 5f UPS peak is larger than ${\mathrm{U}}_{5\mathit{f},5\mathit{f}}$=1.2 eV. This difference is interpreted as mostly due to the spin-orbit splitting of the U 5f state. The U 4f core XPS has shown rather an asymmetric shape with a tail toward larger binding energies (${\mathit{E}}_{\mathit{B}}$). A satellite not directly observable in the experimental spectrum is revealed at \ensuremath{\sim}5.4 eV by deconvolution. Based on an extended Anderson impurity model, it is interpreted as the ``p-d antibonding state.'' The appreciable density of the U 6d state near ${\mathit{E}}_{\mathit{F}}$ strongly influences the photoemission spectra.