The interatomic Auger transitions in compounds containing atomic components with core levels close in energy are studied theoretically and experimentally. The Coulomb transitions of a hole between ...such levels lead to a resonant enhancement of the Auger spectra (with respect to the energy difference between the levels). Interatomic Auger transitions involving high lying levels are formed by shaking up electrons due to the dynamic field of photo holes produced during the transition. These effects are observed experimentally in XPS and Auger spectra of CuInSe2 type materials.
The experimental XPS spectra in CuInSe2 based compounds show intense interatomic CuL3M2,3InN4,5 and CuL3InN4,5V Auger transitions. The interaction of copper 3p and indium 4p levels of similar energy gives a resonant increase in the magnitude of the first Auger transition. Shaking the In 4d electron because of the appearance of a photo hole is the mechanism of the second transition.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The problem of determining the magnitude of the atomic magnetic moments in compounds with rare-earth and transition elements using the X-ray magnetic circular dichroism (XMCD) is investigated. The ...standard sum rules approach usually gives the moment values by several times smaller than their bulk values obtained from the direct magnetic measurements. We attribute this to the strong spin fluctuations in the surface layer which actually formed the soft XMCD signal. A method of determining the value of the local magnetic moments in the presence of strong fluctuations is proposed. The magnetic interactions in La0.5Pr0.2Ca0.3MnO3 are investigated by x-ray absorption spectroscopy, XMCD and bulk magnetization measurements. The proposed procedure is used to determine the values of atomic magnetic moments of transition and rare-earth elements as well as net magnetization on the surface and in the bulk from experimental Mn L2,3 and Pr M4,5 XMCD spectra.
•Strong spin fluctuations at the surface (TEY depth 10nm) reduce the XMCD spectra.•The Mn L2;3 XMCD decomposition show two signals from up and down magnetic moments.•The sum rules give the Mn and Pr magnetization at the surface and in the bulk.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The surface electronic structure of the narrow-gap seminconductor BiTeI exhibits a large Rashba-splitting which strongly depends on the surface termination. Here we report on a detailed investigation ...of the surface morphology and electronic properties of cleaved BiTeI single crystals by scanning tunneling microscopy, photoelectron spectroscopy (ARPES, XPS), electron diffraction (SPA-LEED) and density functional theory calculations. Our measurements confirm a previously reported coexistence of Te- and I-terminated surface areas originating from bulk stacking faults and find a characteristic length scale of ∼100 nm for these areas. We show that the two terminations exhibit distinct types of atomic defects in the surface and subsurface layers. For electronic states resided on the I terminations we observe an energy shift depending on the time after cleavage. This aging effect is successfully mimicked by depositon of Cs adatoms found to accumulate on top of the I terminations. As shown theoretically on a microscopic scale, this preferential adsorbing behaviour results from considerably different energetics and surface diffusion lengths at the two terminations. Our investigations provide insight into the importance of structural imperfections as well as intrinsic and extrinsic defects on the electronic properties of BiTeI surfaces and their temporal stability.
The x-ray absorption near edge structure (XANES) and the x-ray magnetic circular dichroism (XMCD) measurements in the hard X-ray range at the Ni and Mn K edges and Tb, Dy L2, 3 edges were carried out ...in TbNi2Mn and DyNi2Mn in magnetic field up to 6T at 10K. XMCD on the Dy and Tb L-edges reaches 3.2%. The spin and orbital d-projected density of states on Tb and Dy atoms were obtained from the XMCD spectra. The Ni and Mn K-edges absorptions are practically identical in both compounds, as well as the dichroism spectra. The magnitude of dichroism is less than 0.5% and its length of about 50eV. Scattering of outgoing p-wave on magnetic atoms environment is the main source of the K-edge dichroism. Element-specific magnetic hysteresis-loops measurements on TbNi2Mn and DyNi2Mn were performed by X-ray magnetic circular dichroism.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The electron spin density fluctuation theory is developed for disordered alloys. The model contains two types of magnetic atoms characterized by different intra-atomic exchange interactions because ...of their different nearest neighborhood. The microscopic approach allow us to describe the various temperature behaviors of the magnetization of the Fe-Al alloys (25 - 32 at.% Al) observed in experiments. Competition parallel and antiparallel orientations of subsystems Fe(1) and Fe(2) gives rise to a diverse and anomalous temperature behavior of magnetism in partially and strongly disordered alloys.
Resonant photoemission in narrow-band materials is described by the sum of first-and secondorder transitions, their quantum-mechanical interference leads to an increase in the spectrum from the ...valence bands and the appearance of an asymmetric dependence on the photon energy. These effects are studied theoretically and experimentally using the example of three-component intermetallic compounds TbNi2Mnx. The competition between the elastic and inelastic photoemission channels leads to a different dependence of photoemission spectra from nickel and manganese on photon energy. The elastic channel is realized on atoms with large magnetic moments, the inelastic Auger decay occurs on atoms with small moments.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
We propose a theory for the quantitative description of the thermodynamic, magnetic and electronic properties of disordered alloys of transition metals and normal, for example, the system Fe-Al, as ...obtained from melting, and in the form of metastable states produced by mechanical grinding. System of itinerant d-electrons with two constants of the intra-atomic exchange interaction is investigated by the fluctuating field approach. Fundamentally new feature of the system is the presence of several ferrimagnetic solutions, transitions between which give variety to the temperature dependence of the magnetic characteristics of disordered alloys. Results of calculation of the temperature dependences of the magnetic characteristics of iron aluminum alloys are considered as an application of the theory.
Resonant photoemission in narrow-band materials is described by the sum of first-and secondorder transitions, their quantum-mechanical interference leads to an increase in the spectrum from the ...valence bands and the appearance of an asymmetric dependence on the photon energy. These effects are studied theoretically and experimentally using the example of three-component intermetallic compounds TbNi
2
Mn
x
. The competition between the elastic and inelastic photoemission channels leads to a different dependence of photoemission spectra from nickel and manganese on photon energy. The elastic channel is realized on atoms with large magnetic moments, the inelastic Auger decay occurs on atoms with small moments.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The surfaces of crystalline samples of 3d-metals (Mn, Fe, Co, Ni, and
Cu) and their stoichiometric oxides have been studied by Auger
spectroscopy. A correlation between the change in the LVV (L-inner
...level-valence-valence electron transition) Auger intensities and the
change of the squares of the corresponding atomic-magnetic moments has
been observed. This is because of the complicated nature of the Auger
process. That is, the Auger electron emission is a result of the inner
atomic level excitation by electron impact and Auger annihilation of the
inner-level hole. Therefore, the Auger process has been considered a
second-order process, and spin polarization of the valence states has been
taken into account for the LMM (L-inner level-M-inner level-M-inner level
electron transition) Auger spectra of 3d-metals.
The interatomic Auger transitions in compounds containing atomic components with core levels close in energy are studied theoretically and experimentally. The Coulomb transitions of a hole between ...such levels lead to a resonant enhancement of the Auger spectra (with respect to the energy difference between the levels). Interatomic Auger transitions involving high lying levels are formed by shaking up electrons due to the dynamic field of photo holes produced during the transition. These effects were observed experimentally in XPS and Auger spectra of CuInSe2 type materials.
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