Study of the hydrogen stability in evaporated amorphous Si 1− x Sn x :H (0≤ x ≤0.2) alloys by neutron scattering and exodiffusion measurements

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Hydrogen diffusion and densification in amorphous silicon

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Observation Of Orbital Moment In Nio Using Magnetic X-ray Scattering

The spin and orbital contribution to the total magnetization have been measured in NiO by exploiting the polarization dependence of nonresonant x-ray magnetic scattering. Although the orbital moment is usually neglected, we observed that the orbital moment actually plays an important role with a contribution of 17% to the total magnetization density. By performing azimuthal scans, it was found that spin and orbital moments are collinear. © 1999 American Institute of Physics.858 II A48474849Muraki, Y., (1998) Phys. Rev. Lett., 81, p. 582Muraki, Y., (1998) Phys. Rev. Lett., 80, p. 1932Blume, M., Gibbs, D., (1988) Phys. Rev. B, 37, p. 1779Shull, C.G., Strauser, W.A., Wollan, F.O., (1951) Phys. Rev., 83, p. 333Baruchel, J., Schlenker, M., Kuusowa, K., Saito, S., (1981) Philos. Mag. B, 43, p. 853Roth, W., (1960) J. Appl. Phys., 31, p. 2000Bergevin, F.D., Brunel, M., (1972) Phys. Lett., 39 A2, p. 141Brunel, M., Bergevin, F.D., (1981) Acta Crystallogr. A, 37, p. 324Blume, M., (1985) J. Appl. Phys., 57, p. 3615Alperin, H.A., (1962) J. Phys. Soc. Jpn., 17 B-III, p. 12Stunault, A., (1998) J. Synchrotron Radiat., 5, p. 1010Fernandez, V., (1998) Phys. Rev. B, 57, p. 7870Blume, M., (1961) Phys. Rev., 124, p. 9

Distinct Magnetic Phase Transition at the Surface of an Antiferromagnet

In the majority of magnetic systems the surface is required to order at the same temperature as the bulk. In the present Letter, we report a distinct and unexpected surface magnetic phase transition at a lower temperature than the Néel temperature. Employing grazing incidence x-ray resonant magnetic scattering, we have observed the near-surface behavior of uranium dioxide. UO2 is a noncollinear, triple-q, antiferromagnet with the U ions on a face-centered cubic lattice. Theoretical investigations establish that at the surface the energy increase—due to the lost bonds—is reduced when the spins near the surface rotate, gradually losing their component normal to the surface. At the surface the lowest-energy spin configuration has a double-q (planar) structure. With increasing temperature, thermal fluctuations saturate the in-plane crystal field anisotropy at the surface, leading to soft excitations that have ferromagnetic XY character and are decoupled from the bulk. The structure factor of a finite two-dimensional XY model fits the experimental data well for several orders of magnitude of the scattered intensity. Our results support a distinct magnetic transition at the surface in the Kosterlitz-Thouless universality class

Satellite holmium M-edge spectra from the magnetic phase via resonant x-ray scattering

Developing an expression of resonant x-ray scattering (RXS) amplitude which is convenient for investigating the contributions from the higher rank tensor on the basis of a localized electron picture, we analyze the RXS spectra from the magnetic phases of Ho near the $M_{4,5}$ absorption edges. At the $M_5$ edge in the uniform helical phase, the calculated spectra of the absorption coefficient, the RXS intensities at the first and second satellite spots capture the properties the experimental data possess, such as the spectral shapes and the peak positions. This demonstrates the plausibility of the adoption of the localized picture in this material and the effectiveness of the spectral shape analysis. The latter point is markedly valuable since the azimuthal angle dependence, which is one of the most useful informations RXS can provides, is lacking in the experimental conditions. Then, by focusing on the temperature dependence of the spectral shape at the second satellite spot, we expect that the spectrum is the contribution of the pure rank two profile in the uniform helical and the conical phases while that is dominated by the rank one profile in the intermediate temperature phase, so-called spin slip phase. The change of the spectral shape as a function of temperature indicates a direct evidence of the change of magnetic structures undergoing. Furthermore, we predict that the intensity, which is the same order observed at the second satellite spot, is expected at the fourth satellite spot from the conical phase in the electric dipolar transition.Comment: 24 pages, 5 figure

Specific heat of Ce_{0.8}La_{0.2}Al_{3} in magnetic fields: a test of the anisotropic Kondo picture

The specific heat C of Ce_{0.8}La_{0.2}Al_{3} has been measured as a function of temperature T in magnetic fields up to 14 T. A large peak in C at 2.3 K has recently been ascribed to an anisotropic Kondo effect in this compound. A 14-T field depresses the temperature of the peak by only 0.2 K, but strongly reduces its height. The corresponding peak in C/T shifts from 2.1 K at zero field to 1.7 K at 14 T. The extrapolated specific heat coefficient C/T(T->0) increases with field over the range studied. We show that these trends are inconsistent with the anisotropic Kondo model.Comment: 4 pages, 5 figures, ReVTeX + eps

High energy spin excitations in YBa_2 Cu_3 O_{6.5}

Inelastic neutron scattering has been used to obtain a comprehensive description of the absolute dynamical spin susceptibility $\chi'' (q,\omega)$ of the underdoped superconducting cuprate YBa_2 Cu_3 O_{6.5} ($T_c = 52 K$) over a wide range of energies and temperatures ($2 meV \leq \hbar \omega \leq 120 meV$ and $5K \leq T \leq 200K$). Spin excitations of two different symmetries (even and odd under exchange of two adjacent CuO_2 layers) are observed which, surprisingly, are characterized by different temperature dependences. The excitations show dispersive behavior at high energies.Comment: 15 pages, 5 figure