Electron-phonon interaction in n-doped cuprates: an Inelastic X-ray Scattering study

Inelastic x-ray scattering (IXS) with very high (meV) energy resolution has become a valuable spectroscopic tool, complementing the well established coherent inelastic neutron scattering (INS) technique for phonon dispersion investigations. In the study of crystalline systems IXS is a viable alternative to INS, especially in cases where only small samples are available. Using IXS, we have measured the phonon dispersion of Nd_{1.86}Ce_{0.14}CuO_{4+\delta} along the [x,0,0] and [x,x,0] in-plane directions. Compared to the undoped parent compound, the two highest longitudinal optical (LO) phonon branches are shifted to lower energies because of Coulomb-screening effects brought about by the doped charge carriers. An additional anomalous softening of the highest branch is observed around q=(0.2,0,0). This anomalous softening, akin to what has been observed in other compounds, provides evidence for a strong electron-phonon coupling in the electron-doped high-temperature superconductors.Comment: Proceedings of the SATT11 conference, Vietri sul Mare - Italy (March 2002); accepted for publication on Int. J. Mod. Phys.

Doping and temperature dependence of Mn 3d states in A-site ordered manganites

We present a systematic study of the electronic structure in A-site ordered manganites as function of doping and temperature. The energy dependencies observed with soft x-ray resonant diffraction (SXRD) at the Mn L_{2,3} edges are compared with structural investigations using neutron powder diffraction as well as with cluster calculations. The crystal structures obtained with neutron powder diffraction reflect the various orbital and charge ordered phases and show an increase of the Mn-O-Mn bond angle as function of doping and temperature. Cluster calculations show that the observed spectral changes in SXRD as a function of doping are more pronounced than expected from an increase in bandwitdh due to the increase in Mn-O-Mn bond angle, and are best described by holes that are distributed at the neighbouring oxygen ions. These holes are not directly added to the Mn 3d shell, but centered at the Mn site. In contrast, the spectral changes in SXRD as function of temperature are best described by an increase of magnetic correlations. This demonstrates the strong correlations between orbitals and magnetic moments of the 3d states

Magnetic and electronic Co states in layered cobaltate GdBaCo2O5.5-x

We have performed non-resonant x-ray diffraction, resonant soft and hard x-ray magnetic diffraction, soft x-ray absorption and x-ray magnetic circular dichroism measurements to clarify the electronic and magnetic states of the Co3+ ions in GdBaCo2O5.5. Our data are consistent with a 3+ Py Co HS state at the pyramidal sites and a 3+ Oc Co LS state at the octahedral sites. The structural distortion, with a doubling of the a axis (2ap x 2ap x 2ap cell), shows alternating elongations and contractions of the pyramids and indicates that the metal-insulator transition is associated with orbital order in the t2g orbitals of the 3+ Py Co HS state. This distortion corresponds to an alternating ordering of xz and yz orbitals along the a and c axes for the 3+ Py Co . The orbital ordering and pyramidal distortion lead to deformation of the octahedra, but the 3+ Oc Co LS state does not allow an orbital order to occur for the 3+ Oc Co ions. The soft x-ray magnetic diffraction results indicate that the magnetic moments are aligned in the ab plane but are not parallel to the crystallographic a or b axes. The orbital order and the doubling of the magnetic unit cell along the c axis support a non-collinear magnetic structure. The x-ray magnetic circular dichroism data indicate that there is a large orbital magnetic contribution to the total ordered Co moment

Mediterranean Diet as a Shield against Male Infertility and Cancer Risk Induced by Environmental Pollutants: A Focus on Flavonoids

The role of environmental factors in influencing health status is well documented. Heavy metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, dioxins, pesticides, ultrafine particles, produced by human activities put a strain on the body’s entire defense system. Therefore, together with public health measures, evidence-based individual resilience measures are necessary to mitigate cancer risk under environmental stress and to prevent reproductive dysfunction and non-communicable diseases; this is especially relevant for workers occupationally exposed to pollutants and/or populations residing in highly polluted areas. The Mediterranean diet is characterized by a high intake of fruits and vegetables rich in flavonoids, that can promote the elimination of pollutants in tissues and fluids and/or mitigate their effects through different mechanisms. In this review, we collected evidence from pre-clinical and clinical studies showing that the impairment of male fertility and gonadal development, as well as cancers of reproductive system, due to the exposure of organic and inorganic pollutants, may be counteracted by flavonoids

Profile of the U 5f magnetization in U/Fe multilayers

Recent calculations, concerning the magnetism of uranium in the U/Fe multilayer system have described the spatial dependence of the 5f polarization that might be expected. We have used the x-ray resonant magnetic reflectivity technique to obtain the profile of the induced uranium magnetic moment for selected U/Fe multilayer samples. This study extends the use of x-ray magnetic scattering for induced moment systems to the 5f actinide metals. The spatial dependence of the U magnetization shows that the predominant fraction of the polarization is present at the interfacial boundaries, decaying rapidly towards the center of the uranium layer, in good agreement with predictions.Comment: 7 pages, 6 figure

Soft-x-ray resonant scattering from V/Fe (001) magnetic superlattices

The magnetic properties of Fe and V in (n ML V / 5 ML Fe) (001) superlattices (n = 1, 2, and 5 ML) have been investigated by measuring the magnetization dependent scattering of elliptically polarized soft x rays at various scattering angles and for photon energies across the 2p x-ray-absorption edges of both Fe and V. A quantitative estimate of the magnetic moment induced on vanadium is obtained from the analysis of the resonant scattering data. [S0163-1829(99)50842-4]

Optical constants of ferromagnetic iron via 2p resonant magnetic scattering

We have determined the optical constants at the 2p edges of iron by measuring the Bragg scattering from a Fe/V superlattice using elliptically polarized photons whose energies were tuned across the Fe 2p resonances (700-730 eV). The analysis of the Bragg peak displacement as a function of photon energy and sample magnetization, together with standard absorption measurements, allowed to determine the complete dielectric tensor for Fe, including its off-diagonal terms

Pollen extract in association with vitamins provides early pain relief in patients affected by chronic prostatitis/chronic pelvic pain syndrome

The therapeutic efficacy for chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is currently unsatisfactory. The aim of the present study was to assess the safety and efficacy of pollen extract in association with vitamins (DEPROX 500®) in males with CP/CPPS. All patients with a diagnosis of CP/CPPS attending the same urologic centre between March and October 2012 were enrolled in this randomised controlled phase III study. Participants were randomised to receive oral capsules of DEPROX 500® (two capsules every 24 h) or ibuprofen (600 mg, one tablet three times a day) for four weeks. The National Institutes of Health Chronic Prostatitis Symptom Index (NIH-CPSI), International Prostate Symptom Score and Quality of Well-Being (QoL) questionnaires were used. In the intention-to-treat analysis, 87 males (25 class IIIa and 62 class IIIb) with a mean age of 33.6±5.9 years were randomly allocated to the DEPROX 500® (n=41) or ibuprofen (n=46) treatment groups. At the follow-up examination (following one month of treatment), in the DEPROX 500® group, 31/41 patients (75.6%) reported an improvement in quality of life, defined as a reduction of the NIH-CPSI total score by ≥25%, compared with 19/46 (41.3%) in the control group (P=0.002). The greater improvement in the DEPROX 500® group compared with the ibuprofen group was statistically significant (treatment difference in the NIH-CPSI pain domain, -2.14±0.51, P<0.001; QoL scores, P=0.002). All patients were negative at the Meares-Stamey test evaluation. Adverse events were less frequent in the DEPROX 500® group than in the ibuprofen group. The DEPROX 500® treatment significantly improved total symptoms, pain and quality of life compared with ibuprofen in patients with CP/CPPS, without severe side-effects

The spin polarization of Mn atoms in paramagnetic CuMn alloys induced by a Co layer

Copyright © 2009 American Institute of PhysicsUsing the surface, interface, and element specificity of x-ray resonant magnetic scattering in combination with x-ray magnetic circular dichroism, we have spatially resolved the polarization, and hence the spin accumulation in Mn high susceptibility material in close proximity to a ferromagnetic layer. The magnetic polarization of Mn and Cu 3d electrons in paramagnetic CuMn layers is detected in a Co/Cu x /CuMn structure for varying copper layer thicknesses x . The size of the Mn and Cu L2–3-edge dichroism shows a decrease in the polarization for increasing copper thickness indicating the dominant interfacial nature of the Cu and Mn spin polarization. The Mn polarization appears to be much higher than that of Cu