Spectroscopy of stripe order in La1.8Sr0.2NiO4 using resonant soft x-ray diffraction

Strong resonant enhancements of the charge-order and spin-order superstructure-diffraction intensities in La1.8Sr0.2NiO4 are observed when x-ray energies in the vicinity of the Ni L2,3 absorption edges are used. The pronounced photon-energy and polarization dependences of these diffraction intensities allow for a critical determination of the local symmetry of the ordered spin and charge carriers. We found that not only the antiferromagnetic order but also the charge-order superstructure resides within the NiO2 layers; the holes are mainly located on in-plane oxygens surrounding a Ni2+ site with the spins coupled antiparallel in close analogy to Zhang-Rice singlets in the cuprates.     

Human immunoglobulin adsorption investigated by means of quartz crystal microbalance dissipation, atomic force microscopy, surface acoustic wave, and surface plasmon resonance techniques

Time-resolved adsorption behavior of a human immunoglobin G (hIgG) protein on a hydrophobized gold surface is investigated using multitechniques: quartz crystal microbalance/dissipation (QCM-D) technique; combined surface plasmon resonance (SPR) and Love mode surface acoustic wave (SAW) technique; combined QCM-D and atomic force microscopy (AFM) technique. The adsorbed hIgG forms interfacial structures varying in organization from a submonolayer to a multilayer. An "end-on" IgG orientation in the monolayer film, associated with the surface coverage results, does not corroborate with the effective protein thickness determined from SPR/SAW measurements. This inconsistence is interpreted by a deformation effect induced by conformation change. This conformation change is confirmed by QCM-D measurement. Combined SPR/SAW measurements suggest that the adsorbed protein barely contains water after extended contact with the hydrophobic surface. This limited interfacial hydration also contributed to a continuous conformation change in the adsorbed protein layer. The viscoelastic variation associated with interfacial conformation changes induces about 1.5 times overestimation of the mass uptake in the QCM-D measurements. The merit of combined multitechnique measurements is demonstrated.     

Isomer shifts of sp impurities in metallic hosts

Isomer shifts for¹¹⁹Sn and¹²¹Sb impurities in different metallic hosts are compared. In the frame of the Miedema and van der Woude model three contributions to the isomer shifts due to the charge transfer, electron density mismatch and volume adjustment are calculated.     

Electronic and vibrational properties of a novel mixed-valent europium compound: Eu14Cl33

The occurrence of discrete Eu(II) and Eu(III) valence states in Eu₁₄Cl₃₃, is consistently demonstrated from X-ray diffraction data, Mössbauer effect and magnetic susceptibility measurements. The ratio of the mean square amplitudes of lattice vibrations of the Eu(II) and Eu(III) ions deduced from Mössbauer data is in good agreement with the one obtained from X-ray Debye-Waller factors.     

Structural,electronic and magnetic properties of the linear chain compounds CsMI3 (M = V, Cr, Mn) from 129I mössbauer spectroscopy

The crystal structures of the compounds CsVI₃ and CsMnI₃ belong to the space group P6₃/mmc. CsCrI₃ undergoes at 165 K a crystal phase transition from a hexagonal to an orthorhombic structure. The three-dimensional magnetic structure of CsMnI₃ consists of an arrangement of Mn moments parallel to the hexagonal c-axis and coupled antiferromagnetically within the chain. The electronic charge and spin densities in the iodine valence orbitals are deduced from an analysis of the hyperfine interaction parameters measured at the ¹²⁹I nucleus in CsVI₃, CsMnI₃ and CsCrI₃     

Incommensurate magnetic ordering in Sr2Ru(1-x)TixO4

In Sr2RuO4 the spin excitation spectrum is dominated by incommensurate fluctuations at q = (0.3 0.3q(z)), which arise from Fermi-surface nesting. We show that upon Ti substitution, known to suppress superconductivity, a short range magnetic order develops with a propagation vector (0.307 0.307 1). In Sr2Ru0.91Ti0.09O4, the ordered moment points along the c direction. This finding shows that superconducting Sr2RuO4 is extremely close to an incommensurate spin density wave instability.     

Hyperfine interactions on151Eu and57Fe in amorphous EuFe2Si2

The magnetic and quadrupole hyperfine interactions in amorphous EuFe₂Si₂ have been measured using⁵⁷Fe and¹⁵¹Eu Mössbauer spectroscopy. The distributions in the various parameters have been found using the Fourier coefficient method. Novel features of the results are that the Eu charge state (4f occupation number) changes between the crystalline and amorphous phases and that whereas in the crystalline phase neither Eu nor Fe is magnetic, both become so in the amorphous phase.     

Hyperfine structure of Γ6 electronic level in cubic Yb compound from Mössbauer spectroscopy

The hyperfine structure of the Γ₆ electronic level in the cubic compound Cs₂NaYbCl₆ has been observed from the Mössbauer studies of ¹⁷⁰Yb. The effective hyperfine coupling constant is found to be $\text{-10.9±0.1}\text{mm}\text{sec.}$     

Investigation of covalency in CrI3 using Mössbauer spectroscopy of129I

The principal components of the electric field gradient tensor, the transferred hyperfine magnetic field and the isomer shift have been measured in ferromagnetic CrI₃ using the 27.8 keV Mössbauer resonance in¹²⁹I. From these hyperfine parameters we have determined the electron transfer and spin transfer coefficients for CrI₃ and compared these with the ones deduced for other Cr compounds.     

Electric field gradients at57Fe impurities in crystalline NiB phases

The electric field gradient (EFG) parameters are investigated by in-field Mössbauer spectroscopy at⁵⁷Fe doping the crystalline compounds Ni₃B, Ni₂B, Ni₄B₃ and NiB. A preferential substitution of Ni by Fe is found in Ni₃B and Ni₄B₃. The knowledge of q_zz and at both the 3d metal and boron sites /1/ permits to develop a representation of EFG in terms of empirical screened point charges.