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Growth, morphology and electronic properties of epitaxial graphene on vicinal Ir(332) surface. NANOTECHNOLOGY 2020; 31:285601. [PMID: 32244246 DOI: 10.1088/1361-6528/ab866a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Superlattice induced minigaps in graphene band structure due to underlying one-dimensional nanostructuration has been demonstrated. A superperiodic potential can be introduced in graphene if the substrate is periodically structured. The successful preparation of a periodically nanostructured substrate in large scale can be obtained by carefully studying the electronic structure with a spatial averaging technique such as high-energy resolution photoemission. In this work, we present two different growth methods such as temperature programmed growth (TPG) and chemical vapor deposition (CVD) studied by scanning tunnelling microscopy (STM) and low energy electron diffraction (LEED). In both methods, we show that the original steps of Ir(332) have modified with (111) terraces and step bunching after graphene growth. Graphene grows continuously over the terrace and the step bunching areas. We observe that while TPG growth does not give rise to a well-defined surface periodicity required for opening a bandgap, the CVD growth does. By combining with angle-resolved photoemission spectroscopy (ARPES) measurements, we correlate the obtained spatial periodicity to observed band gap opening in graphene.
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Evidence for Weakly Correlated Oxygen Holes in the Highest-T_{c} Cuprate Superconductor HgBa_{2}Ca_{2}Cu_{3}O_{8+δ}. PHYSICAL REVIEW LETTERS 2017; 119:057001. [PMID: 28949729 DOI: 10.1103/physrevlett.119.057001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Indexed: 06/07/2023]
Abstract
We study the electronic structure of HgBa_{2}Ca_{2}Cu_{3}O_{8+δ} (Hg1223; T_{c}=134 K) using photoemission spectroscopy (PES) and x-ray absorption spectroscopy (XAS). Resonant valence band PES across the O K edge and Cu L edge identifies correlation satellites originating in O 2p and Cu 3d two-hole final states, respectively. Analyses using the experimental O 2p and Cu 3d partial density of states show quantitatively different on-site Coulomb energy for the Cu site (U_{dd}=6.5±0.5 eV) and O site (U_{pp}=1.0±0.5 eV). Cu_{2}O_{7}-cluster calculations with nonlocal screening explain the Cu 2p core level PES and Cu L-edge XAS spectra, confirm the U_{dd} and U_{pp} values, and provide evidence for the Zhang-Rice singlet state in Hg1223. In contrast to other hole-doped cuprates and 3d-transition metal oxides, the present results indicate weakly correlated oxygen holes in Hg1223.
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Ultrafast Atomic Diffusion Inducing a Reversible (2sqrt[3]×2sqrt[3])R30°↔(sqrt[3]×sqrt[3])R30° Transition on Sn/Si(111)∶B. PHYSICAL REVIEW LETTERS 2015; 114:196101. [PMID: 26024183 DOI: 10.1103/physrevlett.114.196101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Indexed: 06/04/2023]
Abstract
Dynamical phase transitions are a challenge to identify experimentally and describe theoretically. Here, we study a new reconstruction of Sn on silicon and observe a reversible transition where the surface unit cell divides its area by a factor of 4 at 250 °C. This phase transition is explained by the 24-fold degeneracy of the ground state and a novel diffusive mechanism, where four Sn atoms arranged in a snakelike cluster wiggle at the surface exploring collectively the different quantum mechanical ground states.
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Nonpareil Yb behavior in YbMn6Ge(6-x)Sn(x). PHYSICAL REVIEW LETTERS 2013; 111:096402. [PMID: 24033054 DOI: 10.1103/physrevlett.111.096402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Indexed: 06/02/2023]
Abstract
We investigate the temperature dependence of the Yb valence in YbMn6Ge1.8Sn4.2 and YbMn6Ge1.6Sn4.4 using resonant inelastic x-ray scattering experiments. Yb is found to be in an intermediate valent state in the whole investigated temperature range (10-450 K). We thus prove that the unusually high magnetic ordering temperature of Yb (∼60 and 90 K for x=4.2 and 4.4, respectively) involves an intermediate valent Yb, an unprecedentedly observed phenomenon. Further, an anomalous increase in the Yb valence is observed upon cooling. A scenario is proposed to explain this unusual behavior. It is based on the presence of magnetically ordered Mn moments and on an Anderson Hamiltonian with a Zeeman term modeling the magnetic interactions.
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Understanding the insulating nature of alkali-metal/Si(111):B interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:094004. [PMID: 23400003 DOI: 10.1088/0953-8984/25/9/094004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We have recently revisited the phase diagram of alkali-metal/Si(111):B semiconducting interfaces previously suggested as the possible realization of a Mott-Hubbard insulator on a triangular lattice. The insulating character of the 2√[3] × 2√[3]R30 surface reconstruction observed at the saturation coverage, i.e. 0.5 ML, has been shown to find its origin in a giant alkali-metal-induced vertical distortion. Low energy electron diffraction, photoemission spectroscopy and scanning tunneling microscopy and spectroscopy experiments coupled with linear augmented plane-wave density functional theory calculations allow a full understanding of the k-resolved band structure, explaining both the inhomogeneous charge transfers into an Si-B hybridized surface state and the opening of a band gap larger than 1 eV. Moreover, √[3] × √[3]R30, 3 × 3 and 2√[3] × 2√[3]R30 surface reconstructions observed as a function of coverage may reveal a filling-controlled transition from a half-filled correlated magnetic material to a strongly distorted band insulator at saturation.
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Giant alkali-metal-induced lattice relaxation as the driving force of the insulating phase of alkali-metal/Si(111):B. PHYSICAL REVIEW LETTERS 2011; 107:187603. [PMID: 22107674 DOI: 10.1103/physrevlett.107.187603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Indexed: 05/31/2023]
Abstract
Ab initio density-functional theory calculations, photoemission spectroscopy (PES), scanning tunneling microscopy, and spectroscopy (STM, STS) have been used to solve the 2sqrt[3]×2sqrt[3]R30 surface reconstruction observed previously by LEED on 0.5 ML K/Si:B. A large K-induced vertical lattice relaxation occurring only for 3/4 of Si adatoms is shown to quantitatively explain both the chemical shift of 1.14 eV and the ratio 1/3 measured on the two distinct B 1s core levels. A gap is observed between valence and conduction surface bands by ARPES and STS which is shown to have mainly a Si-B character. Finally, the calculated STM images agree with our experimental results. This work solves the controversy about the origin of the insulating ground state of alkali-metal/Si(111):B semiconducting interfaces which were believed previously to be related to many-body effects.
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Phonon contribution to the lifetime of surface state quasiparticles confined in nanopyramids. PHYSICAL REVIEW LETTERS 2010; 104:016802. [PMID: 20366379 DOI: 10.1103/physrevlett.104.016802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Indexed: 05/29/2023]
Abstract
We present a scanning tunneling microscopy investigation of the dynamics of hot electrons and holes in Ag pyramidal nanostructures. The geometry of the nanostructure leads to a strong reduction of the decay mechanism into the bulk states and then to a large reflection coefficient of the surface electronic waves. Therefore, in contrast to quantum corrals and adatom islands which show a dominant lossy scattering contribution to the linewidth, the narrow observed structures in the differential conductivity spectra reveal the expected linewidth minimum at the Fermi energy. The electron-phonon contribution to the lifetime is shown to be dominant, in agreement with previous photoemission measurements.
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Surface-state bipolaron formation on a triangular lattice in the sp-type alkali-metal/Si(111) Mott insulator. PHYSICAL REVIEW LETTERS 2009; 103:046804. [PMID: 19659382 DOI: 10.1103/physrevlett.103.046804] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Indexed: 05/28/2023]
Abstract
We report on new low-energy electron diffraction, scanning tunneling microscopy, and angle-resolved photoemission spectroscopy studies of alkali-metal/Si(111) previously established as having a Mott-insulating ground state at surface. The observation of a strong temperature dependent Franck-Condon broadening of the surface band together with the novel sqrt[3] x sqrt[3] --> 2(sqrt[3] x sqrt[3]) charge and lattice ordering below 270 K evidence a surface charge density wave in the strong electron-phonon coupling limit (g approximately 8). Both the adiabatic ratio variant Planck's over 2piomega_{0}/t approximately 0.8 and the effective pairing energy V_{eff} = U - 2gvariant Planck's over 2piomega_{0} approximately -800 meV are consistent with the possible formation of a bipolaronic insulating phase consisting of alternating doubly occupied and unoccupied dangling bonds as expected in the Holstein-Hubbard model.
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Structural origin of the Sn 4d core level line shape in Sn/Ge(111)-(3x3). PHYSICAL REVIEW LETTERS 2008; 100:026103. [PMID: 18232889 DOI: 10.1103/physrevlett.100.026103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2007] [Indexed: 05/25/2023]
Abstract
High-resolution photoemission of the Sn 4d core level of Sn/Ge(111)-(3x3) resolves three main components in the line shape, which are assigned to each of the three Sn atoms that form the unit cell. The line shape found is in agreement with an initial state picture and supports that the two down atoms are inequivalent. In full agreement with these results, scanning tunnel microscopy images directly show that the two down atoms are at slightly different heights in most of the surface, giving rise to an inequivalent-down-atoms (3x3) structure. These results solve a long-standing controversy on the interpretation of the Sn 4d core-level line shape and the structure of Sn/Ge(111)-(3x3).
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Observation of a Mott insulating ground state for Sn/Ge(111) at low temperature. PHYSICAL REVIEW LETTERS 2006; 96:126103. [PMID: 16605931 DOI: 10.1103/physrevlett.96.126103] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2005] [Indexed: 05/08/2023]
Abstract
We report an investigation on the properties of 0.33 ML of Sn on Ge(111) at temperatures down to 5 K. Low-energy electron diffraction and scanning tunneling microscopy show that the (3x3) phase formed at approximately 200 K, reverts to a new ((square root 3)x(square root 3))R30 degrees phase below 30 K. The vertical distortion characteristic of the (3x3) phase is lost across the phase transition, which is fully reversible. Angle-resolved photoemission experiments show that, concomitantly with the structural phase transition, a metal-insulator phase transition takes place. The ((square root 3)x(square root 3))R30 degrees ground state is interpreted as the formation of a Mott insulator for a narrow half-filled band in a two-dimensional triangular lattice.
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Comment on "fermi gap stabilization of an incommensurate two-dimensional superstructure". PHYSICAL REVIEW LETTERS 2006; 96:029701; discussion 029702. [PMID: 16486663 DOI: 10.1103/physrevlett.96.029701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Indexed: 05/06/2023]
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12
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Hybridization effects in unoccupied 4f states of Ce compounds. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 53:7030-7034. [PMID: 9982148 DOI: 10.1103/physrevb.53.7030] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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13
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Photoemission studies of the electronic properties of the Ce/Fe(100) and Ce/Fe(110) interfaces: Formation of a strongly hybridized cerium phase. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 53:5015-5023. [PMID: 9984065 DOI: 10.1103/physrevb.53.5015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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14
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Can we describe the spectral function of CeRh3 by a band picture? PHYSICAL REVIEW LETTERS 1994; 73:2005. [PMID: 10056944 DOI: 10.1103/physrevlett.73.2005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Resonant inverse photoemission: A new probe of correlated systems. PHYSICAL REVIEW LETTERS 1994; 72:1252-1255. [PMID: 10056661 DOI: 10.1103/physrevlett.72.1252] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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16
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Correlation between the Kondo temperature and the photoemission spectral function in the CeSix (1.6 <= x <= 2) system. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:10599-10601. [PMID: 10007349 DOI: 10.1103/physrevb.48.10599] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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17
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Comment on "Temperature-invariant photoelectron spectra in cerium heavy-fermion compounds: Inconsistencies with the Kondo model". PHYSICAL REVIEW LETTERS 1993; 70:1179. [PMID: 10054306 DOI: 10.1103/physrevlett.70.1179] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Photoemission near the Fermi energy in one dimension. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 46:13624-13626. [PMID: 10003416 DOI: 10.1103/physrevb.46.13624] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Spectroscopic signatures of phase transitions in a charge-density-wave system: 1T-TaS2. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 46:7407-7412. [PMID: 10002476 DOI: 10.1103/physrevb.46.7407] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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21
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Evidence of a Kondo scale from the temperature dependence of inverse photoemission spectroscopy of CePd3. PHYSICAL REVIEW LETTERS 1992; 68:2656-2659. [PMID: 10045454 DOI: 10.1103/physrevlett.68.2656] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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22
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Temperature-dependent pseudogap and electron localization in 1T-TaS2. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 45:1462-1465. [PMID: 10001632 DOI: 10.1103/physrevb.45.1462] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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23
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Unusual photoemission spectral function of quasi-one-dimensional metals. PHYSICAL REVIEW LETTERS 1991; 67:3144-3147. [PMID: 10044652 DOI: 10.1103/physrevlett.67.3144] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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24
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High-energy spectroscopy in uranium-based systems. PHYSICAL REVIEW. B, CONDENSED MATTER 1991; 44:10455-10460. [PMID: 9999068 DOI: 10.1103/physrevb.44.10455] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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25
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Comment on "Surface electronic structure of Ce in the alpha and gamma phase". PHYSICAL REVIEW. B, CONDENSED MATTER 1991; 44:9108-9109. [PMID: 9998885 DOI: 10.1103/physrevb.44.9108] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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26
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Electron spectroscopy in the URh3Bx system. PHYSICAL REVIEW. B, CONDENSED MATTER 1991; 43:1338-1344. [PMID: 9997382 DOI: 10.1103/physrevb.43.1338] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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27
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LIII-edge spectroscopy on cerium-based intermediate-valent compounds. PHYSICAL REVIEW. B, CONDENSED MATTER 1991; 43:1391-1398. [PMID: 9997388 DOI: 10.1103/physrevb.43.1391] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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28
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Photoelectron spectroscopy towards the meV range: Observation of the superconducting transition in Nb3Al. PHYSICAL REVIEW. B, CONDENSED MATTER 1991; 43:1216-1218. [PMID: 9996329 DOI: 10.1103/physrevb.43.1216] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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29
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Valence admixture in the EuxRh1-x amorphous alloys. PHYSICAL REVIEW. B, CONDENSED MATTER 1989; 39:10665-10668. [PMID: 9947874 DOI: 10.1103/physrevb.39.10665] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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30
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High-energy-spectroscopy study of the Pd-Ce system. PHYSICAL REVIEW. B, CONDENSED MATTER 1988; 38:3766-3772. [PMID: 9946746 DOI: 10.1103/physrevb.38.3766] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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31
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Electronic configuration of cerium in amorphous alloys investigated by x-ray absorption spectroscopy. PHYSICAL REVIEW. B, CONDENSED MATTER 1986; 34:2176-2181. [PMID: 9939903 DOI: 10.1103/physrevb.34.2176] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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