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In this paper we review a variety of spectra for Ce compounds, i.e. valence photoemission and inverse valence photoemission, core-level and resonant photoemission as well as X-ray absorption, X-ray emission and X-ray magnetic circular dichroism (MCD). Those spectra are theoretically analysed by using the single-site Anderson model with various final state interactions. In the first part of the present article we are considering intermetallic Ce compounds, especially several Ce–Pd ordered phases, as well as CeRh3, CeSn3 and CeFe2. In the second part we focus on insulating Ce compounds like CeF3 as well as related systems like Ce oxides. Also we compare Ce hydroxides to other rare-earth hydroxides. Discussions are given on the physical information derived from the analysis, especially through a few key parameters of an extended version of the previously considered Anderson model. Those parameters (i.e. the Coulomb interaction Ufd between 5d and 4f electrons as well as the core hole potential -Udc acting on the 5d electron) have necessarily to be taken into account in order to interpret the experimental L3 X-ray absorption spectra. Another important point stressed in the present paper is the surface/bulk sensitivities of the various spectra to be investigated and theoretically analysed. Also similarities and differences in spectral features between metallic and insulating systems are pointed out. [ABSTRACT FROM AUTHOR]

The bidimensionnal character of thin magnetic films deposited on single-crystal substrates, together with the occurrence of singular crystallographic structures, often confer on these systems electronic properties that cannot be found in bulk solids. For example, thin Ni layers deposited on Cu(001) present a perpendicular magnetic anisotropy in a very wide thickness range. We will show that this can be explained by a distorted structure of Ni, originating from the strain induced by the epitaxy on the Cu substrate. In this field of 2D magnetism, nanostructures are now investigated. Thin Fe layers on MgO(001) were cut into stripes by the "atomic saw" method: a compression of the substrate induces a dislocation slipping which saws both the substrate and the Fe film in regular and separated ribbons. The observed perpendicular to the stripes magnetization easy axis will be explained by a structural relaxation occurring during the structuration process. In these two studies, a precise structural characterization and simple magnetoelastic models allow one to describe the magnetic behaviors of these systems. [ABSTRACT FROM AUTHOR]

Motivated by the different behaviour of Sn/Si(1 1 1) and Sn/Ge(1 1 1) in their metal-insulator transition, we have explored the possibility of growing Sn on an ultra-thin Ge layer strained on top of a Si(1 1 1) substrate. We have demonstrated by scanning tunneling microscopy and low energy electron diffraction that a ( 2 3 × 2 3 ) R30° reconstruction can be stabilized under adequate growth conditions. The size of the reconstructed domains increases progressively up to a coverage of 1.3 monolayer of Sn, as determined by a combined study of scanning tunneling microscopy and core level spectroscopy. This coverage differs from that of Sn/Si(1 1 1) and Sn/Ge(1 1 1) exhibiting Mott phases. Angle resolved photoemission shows that the highly strained reconstruction is a band insulator, with a surface state dispersing roughly between 1300 and 2300 meV of binding energy. [ABSTRACT FROM AUTHOR]

Abstract: The surface structure of alkali doped Si(111):B ultra-thin films has been studied by low-energy electron diffraction (LEED), X-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy (STM). A comparative study of K/Si(111)-3×1 and K/Si(111):B- interfaces allowed us to determine the saturation coverage to be 0.5 monolayer in the later case. The -surface reconstruction is shown to be a common property of pure K, Rb, Cs materials and K0.4Rb0.6 alloys but progressively disappears if Rb is replaced by Ca. Taking into account the existence of two distinct boron sites in the ratio 1/3 as seen from B-1s core levels spectra, LAPW-DFT calculations have been carried out in order to optimize the atomic structure. As a result, alkali adatoms are shown to form trimers leading to a large modulation of the Siccompanied by an inhomogeneous doping of the dangling bonds in agreement with voltage dependent STM images. [Copyright &y& Elsevier]

We investigate the bismuth (111) surface by means of time and angle resolved photoelectron spectroscopy. The parallel detection of the surface states below and above the Fermi level reveals a giant anisotropy of the spin-orbit spitting. These strong deviations from the Rashba-like coupling cannot be treated in k · p perturbation theory. Instead, first principles calculations could accurately reproduce the experimental dispersion of the electronic states. Our analysis shows that the giant anisotropy of the spin-orbit splitting is due to a large out-of plane buckling of the spin and orbital texture. [ABSTRACT FROM AUTHOR]

Gold intercalation between a buffer layer and a graphene monolayer of epitaxial graphene on SiC(OOOl) leads to the formation of small aggregates of clusters. Angle-resolved photoemission spectroscopy measurements reveal that these clusters preserve the linear dispersion of the graphene quasiparticles and surprisingly increase their Fermi velocity. They also strongly modify the band structure of graphene around the van Hove singularities by a strong extension without charge transfer. These results give new insight on the role of the intercalant in the renormalization of the bare electronic band structure of graphene usually observed in graphite and graphene intercalation compounds. [ABSTRACT FROM AUTHOR]

In combining spin- and symmetry-resolved photoemission, magnetotransport measurements and ab initio calculations we detangled the electronic states involved in the electronic transport in Fe1-xCox(001)/MgO/Fe1-xCox(001) magnetic tunnel junctions. Contrary to previous theoretical predictions, we observe a large reduction in TMR (from 530 to 200% at 20 K) for Co content above 25 atomic % as well as anomalies in the conductance curves. We demonstrate that these unexpected behaviors originate from a minority spin state with Δ1 symmetry that exists below the Fermi level for high Co concentration. Using angle-resolved photoemission, this state is shown to be a two-dimensional state that occurs at both Fe1-xCox(001) free surface, and more importantly at the interface with MgO. The combination of this interface state with the peculiar density of empty states due to chemical disorder allows us to describe in details the complex conduction behavior in this system. [ABSTRACT FROM AUTHOR]

We report the observation of a nontrivial spin texture in Dirac node arcs, i.e., novel topological objects formed when Dirac cones of massless particles extend along an open one-dimensional line in momentum space. We find that such states are present in all the compounds of the tetradymite M2Te2X family (M=Ti, Zr, or Hf and X=P or As) regardless of the weak or strong character of the topological invariant. The Dirac node arcs in tetradymites are thus the simplest possible textbook example of a type-I Dirac system with a single spin-polarized node arc. [ABSTRACT FROM AUTHOR]

The ability of the full Heusler alloy Co1.5Fe1.5Ge(001) (CFG) to be a Half-Metallic Magnetic (HMM) material is investigated. Epitaxial CFG(001) layers were grown by molecular beam epitaxy. The results obtained using electron diffraction, X-ray diffraction, and X-ray magnetic circular dichroism are consistent with the full Heusler structure. The pseudo-gap in the minority spin density of state typical in HMM is examined using spin-resolved photoemission. Interestingly, the spin polarization found to be negative at EF in equimolar CoFe(001) is observed to shift to positive values when inserting Ge in CoFe. However, no pseudo-gap is found at the Fermi level, even if moderate magnetization and low Gilbert damping are observed as expected in HMM materials. Magneto-transport properties in MgO-based magnetic tunnel junctions using CFG electrodes are investigated via spin and symmetry resolved photoemission. [ABSTRACT FROM AUTHOR]