Measured distortions of the $\mathrm{Mn}\ensuremath{-}\mathrm{O}$ bond length distribution from x-ray-absorption fine-structure measurements are found to relate linearly doped hole concentration $x$ at room temperature in ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$. Comparison above and below ${T}_{c}$ for colossal magnetoresistor (CMR) samples gives an estimate number delocalized holes ${n}_{\mathrm{dh}}$, we find that...

The reliability of the structural parameters obtained from x-ray-absorption fine-structure (XAFS) spectra strongly depends on quality standards used in data analyses. We have compared about 30 isolated pair standards, extracted experimental data, with those generated by feff5 code. absorbing atoms range Ni (Z=28) to Pb (Z=82) and backscattering O (Z=8) Au (Z=79). In general, good agreement is achieved, typical errors 0.005 \AA{} for nearest-neighbor distances R. Significant differences are...

New synthetic procedures for the preparation of Ce(cot)2, cerocene, from [Li(thf)4][Ce(cot)2], and Ce2(cot)3 in high yield purity are reported. Heating solid Ce(cot)2 yields COT while heating with an excess C6D6 to 65 °C over four months Ce(cot)2. The state magnetic susceptibility data these three organocerium compounds show that behaves as a TIP (temperature independent paramagnet) temperature range 5−300 K, shows spin carriers antiferromagnetically coupled below 10 K; above individual...

Understanding the nature of covalent (band-like) vs ionic (atomic-like) electrons in metal oxides continues to be at forefront research physical sciences. In particular, development a coherent and quantitative model bonding electronic structure for lanthanide dioxides, LnO2 (Ln = Ce, Pr, Tb), has remained considerable challenge both experiment theory. Herein, relative changes mixing between O 2p orbitals Ln 4f 5d are evaluated quantitatively using K-edge X-ray absorption spectroscopy (XAS)...

The hydroxypyridinone ligand 3,4,3-LI(1,2-HOPO) is a promising agent for biological decorporation of radionuclides, and allows spectroscopic detection many lanthanide (Ln) actinide (An) species via sensitized luminescence. Despite the manifest uses this ligand, structural thermodynamic properties its complexes across An series remain understudied. Theoretical investigations binding An(III) An(IV) ions, from actinium to einsteinium, by as well experimental extended X-ray absorption fine...

Oscillatory structure is found in the atomic background absorption x-ray-absorption fine-structure (XAFS) measurements. This XAFS (AXAFS) arises from scattering within an embedded atom, and analogous to Ramsauer-Townsend effect. Calculations measurements confirm existence of AXAFS show that it can dominate contributions such as multielectron excitations. The sensitive chemical effects thus provides a probe bonding exchange on potential.

We report a systematic study of the face-centered-cubic compounds $\mathrm{Yb}X{\mathrm{Cu}}_{4}$ $(X=\mathrm{Ag},$ Au, Cd, Mg, Tl, and Zn), as well their corresponding nonmagnetic analogues $\mathrm{Lu}X{\mathrm{Cu}}_{4}.$ X-ray diffraction, heat capacity, magnetic susceptibility, high-field magnetization, electrical resistivity, Hall effect, ${L}_{\mathrm{III}}$-edge absorption measurements have been performed. The Kondo temperatures that range from about 10 K to nearly 1000 K. Although...

Extended x-ray absorption fine-structure (EXAFS) data collected in the fluorescence mode are susceptible to an apparent amplitude reduction due self-absorption of fluorescing photon by sample before it reaches a detector. Previous treatments have made simplifying assumption that effect EXAFS on correction term is negligible, and samples thick limit. We present nearly exact treatment can be applied for any thickness or concentration, retains oscillations term.

Bulk, single crystal, and metal-organic chemical-vapor deposition thin-film samples of ${\mathrm{Gd}}_{0.67}$ ${\mathrm{Ca}}_{0.33}$ ${\mathrm{MnO}}_{3}$ were prepared examined for their electrical, magnetic, structural properties. is ferrimagnetic with a transition temperature between 50 80 K compensation about 15 K. A molecular field model ferromagnetic manganese sublattice antiparallel to the gadolinium qualitatively explains magnetism data. large high-field susceptibility observed at 5...

X-ray-absorption fine-structure measurements from the Mn and La $K$ edges of samples ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ $(x=\stackrel{\ensuremath{\rightarrow}}{0}1)$ are presented as a function temperature. In insulating state, distortions Mn-O environment found to be linear with calcium concentration $x.$ These consistent model where individual ${\mathrm{Mn}}^{3+}$ sites have strong Jahn-Teller (JT) while ${\mathrm{Mn}}^{4+}$ do not, although intermediate...

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation L. Downward, C. H. Booth, W. Lukens, F. Bridges; A Variation of the F‐Test for Determining Statistical Relevance Particular Parameters in EXAFS Fits. AIP Conf. Proc. 2 February 2007; 882 (1): 129–131. https://doi.org/10.1063/1.2644450 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends...

Kondo coupling of $f$ and conduction electrons is a common feature $f$-electron intermetallics. Similar effects should occur in carbon ring systems (metallocenes). Evidence for $\mathrm{Ce}({\mathrm{C}}_{8}{\mathrm{H}}_{8}{)}_{2}$ (cerocene) the ytterbocene $\mathrm{Cp}^{*}{}_{2}\mathrm{Yb}(\mathrm{bipy})$ reported from magnetic susceptibility ${L}_{\mathrm{III}}$-edge x-ray absorption spectroscopy. These well-defined provide new way to study effect on nanoscale, generate insight into...

Partial ytterbium f-orbital occupancy (i.e., intermediate valence) and open-shell singlet formation are established for a variety of bipyridine diazabutadiene adducts with decamethylytterbocene, (C(5)Me(5))(2)Yb, abbreviated as Cp*(2)Yb. Data used to support this claim include valence measurements using Yb L(III)-edge X-ray absorption near-edge structure spectroscopy, magnetic susceptibility, complete active space self-consistent field (CASSCF) multiconfigurational calculations, well...

Multiconfigurational, intermediate valent ground states are established in several methyl-substituted bipyridine complexes of bis(pentamethylcyclopentadienyl)ytterbium, Cp2*Yb (Me(x)-bipy). In contrast to Cp2*Yb(bipy) and other substituted-bipy complexes, the nature both state first excited altered by changing position methyl or dimethyl substitutions on rings. particular, certain result multiconfigurational, open-shell singlet state. These conclusions reached after consideration...

Uranium and plutonium’s 5f electrons are tenuously poised between strongly bonding with ligand spd-states residing close to the nucleus. The unusual properties of these elements their compounds (e.g., six different allotropes elemental plutonium) widely believed depend on related attributes f-orbital occupancy delocalization for which a quantitative measure is lacking. By employing resonant X-ray emission spectroscopy (RXES) absorption near-edge structure (XANES) making comparisons specific...

The electronic structure and associated magnetic properties of the 1,10-phenanthroline adducts Cp*2Yb are dramatically different from those 2,2′-bipyridine adducts. monomeric phenanthroline ground state triplets that based upon trivalent Yb(III), f13, (phen•– ) only weakly exchange coupled, which is in contrast to bipyridine whose states multiconfigurational, open-shell singlets ytterbium intermediate valent (J. Am. Chem. Soc 2009, 131, 6480; J. 2010, 132, 17537). origin these physical...

Electrochemical experiments performed on the complex CeIV[2-(tBuNO)py]4, where [2-(tBuNO)py]− = N-tert-butyl-N-2-pyridylnitroxide, indicate a 2.51 V stabilization of 4+ oxidation state Ce compared to [nBu4N]2[Ce(NO3)6] in acetonitrile and 2.95 standard potential for ion under aqueous conditions. Density functional theory calculations suggest that this preference higher is result tetrakis(nitroxide) ligand framework at cation, which allows effective electron donation into, partial covalent...

Cerium compounds have played vital roles in organic, inorganic, and materials chemistry due to their reversible redox between trivalent tetravalent oxidation states. However, attempts rationally access molecular cerium complexes both states been frustrated by unpredictable reactivity cerium(III) chemistry. Such reactions are limited steric saturation at the metal ion, which can result high energy activation barriers for electron transfer. An alternative approach has realized using a rare...

Unequivocal experimental evidence for carbon 2p and cerium 4f orbital mixing in cerocene, Ce(C₈H₈)₂is provided from K-edge Ce M_5,4-edge X-ray absorption spectroscopies corroborated with DFT configuration interaction calculations.

We report measurements of the low-temperature specific-heat coefficient $\ensuremath{\gamma}{=C}_{p}(T)/T,$ cell volume $V(T),$ Hall ${R}_{H}(T),$ and valence ${z=2+n}_{f}$ [where Yb hole occupation ${n}_{f}(T)$ was determined from $\mathrm{Yb}{\ensuremath{-}L}_{3}$ x-ray absorption] single crystals ${\mathrm{YbIn}}_{1\ensuremath{-}x}{\mathrm{Ag}}_{x}{\mathrm{Cu}}_{4}.$ Alloying ${\mathrm{YbInCu}}_{4}$ with Ag increases temperature ${T}_{s}(x)$ first-order isomorphic phase transition causes...

The combined local structure techniques, extended x-ray absorption fine and neutron pair distribution function analysis, have been used for temperatures 4< or =T< =330 K to rule out a large Jahn-Teller (JT) distortion of the Co-O bond in La1-xSrxCoO3 significant fraction Co sites (x< =0.35), indicating few, if any, JT-active, singly occupied e_{g} exist.

Abstract Ligand reorganization has been shown to have a profound effect on the outcome of cerium redox chemistry. Through use tethered, tripodal, trianionic nitroxide ligand, [((2‐ t BuNOH)C 6 H 4 CH 2 ) 3 N] 3− (TriNO x ), controlled chemistry at was accomplished, and typically reactive complexes tetravalent were isolated. These included rare cationic [Ce(TriNO )thf][BAr F ], in which Ar =3,5‐(CF ‐C , )py][OTf]. A complete Ce–halide series, Ce(TriNO )X, X=F − Cl Br I also synthesized. The...