Rotational motions of NH2 groups have been observed in the three known solid phases of KNH2 by means of quasielastic neutron scattering. The observed intensities of the elastic and quasielastic components can be accounted for by various reorientational jump models between equivalent equilibrium orientations of the NH2 ion: 180° jumps about the molecular axis (monoclinic phase); 90° jumps about the fourfold crystal axis (tetragonal phase); most probably 120° jumps about the threefold axes (cubic phase). In some cases preliminary values of residence time have been obtained from lineshape fits.

Neutron inelastic scattering experiments have been performed on a polycrystalline sample of CeC2 to obtain information on the crystalline electric field level structure and the exchange interaction. The measurements in the paramagnetic phase yield the Gamma t7(2) doublet as ground state and the Gamma t6 doublet at 7 meV and the Gamma t7(1) doublet at 18 meV as excited states. From the measurement in the magnetically ordered state the authors obtain the molecular field parameter lambda =(2.2+or-0.1)*1025 Oe2 erg-1.

AbstractSeveral three‐parameter analyses are performed on β‐FeSO4, α‐FeSO4, α‐NiSO4, and α‐MnSOsb4 by selecting the exchange interactions among the set (J1, J2, J3, J4). These compounds disclose different spin configurations. As input data the experimental values for TN,χ(TN) are used and the second moments of the energy distributions of neutrons scattered by polycrystalline samples in their paramagnetic state. It is possible to determine the significant parameters. It is concluded that, in this series of compounds, the interactions extend up to the fourth neighbours, although the relative importance of the various parameters depends strongly on the ordering type.

AbstractThe various magnetic structures compatible with the crystallographic symmetry in the anhydrous sulphates and selenates of the 3d transition metals are determined using the matrix method of Bertaut. The stability conditions and the minimum range of the magnetic interactions needed to stabilize the different configurations are derived.

physica status solidi (b)Volume 98, Issue 2 p. K171-K174 Short Note Localized Vibrations of Interstitial Hydrogen Impurities in F.C.C. ξ-Cerium W. Wegener, W. Wegener Neutron Physics Department, S.C.K./C.E.N., Mol Search for more papers by this authorP. Vorderwisch, P. Vorderwisch Hahn-Meitner-Institut für Kernforschung, Berlin Search for more papers by this authorS. Hautecler, S. Hautecler Neutron Physics Department, S.C.K./C.E.N., Mol Search for more papers by this author W. Wegener, W. Wegener Neutron Physics Department, S.C.K./C.E.N., Mol Search for more papers by this authorP. Vorderwisch, P. Vorderwisch Hahn-Meitner-Institut für Kernforschung, Berlin Search for more papers by this authorS. Hautecler, S. Hautecler Neutron Physics Department, S.C.K./C.E.N., Mol Search for more papers by this author First published: 1 April 1980 https://doi.org/10.1002/pssb.2220980267Citations: 10 Boeretang 200, B-2400 Mol, Belgium. D-1000 Berlin (West) 39. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat References 1 T. Springer, in: Hydrogen in Metals I. Basic Properties, Topics in Applied Physics, Vol. 28, Ed. G. Alefeld and J. Völkl, Springer, Berlin/Heidelberg/New York 1978. 2 P. Vorderwisch and S. Hautecler, Phys. stat. sol. (b) 64, 495 (1974). P. Vorderwisch, S. Hautecler, and H. Deekers, Phys. stat. sol. (b) 65, 171 (1974). 3 D. G. Hunt and D. K. Ross, J. less-common Metals 49, 169 (1976). 4 C. J. Glinka, J. M. Rowe, J. J. Rush, G. G. Libowitz, and A. Maeland, Solid State Commun. 22, 541 (1977). 5 P. Vorderwisch, S. Hautecler, and W. D. Teuchert, Solid State Commun. 25, 213 (1978). 6 C. E. Lundin, Trans. AIME 236, 978 (1966). 7 P. Vorderwisch, S. Hautecler, and J. B. Suck, Phys. stat. sol. (b) 94, 569 (1979). 8 J. Hauck, in: Proc. Internat. Meeting Hydrogen in Metals, Münster, March 1979; Ber. Bunsenges. Phys. Chem., to be published. 9 G. Blaesser, J. Peretti, and G. Toth, Phys. Rev. 171, 665 (1968). 10 C. Stassis, T. Gould, O. D. Mc Masters, K. A. Gschneider, Jr., and R. M. Nicklow, Phys. Rev. B 19, 5746 (1979). 11 S. M. Shapiro, J. D. Axe, R. J. Birgeneau, J. M. Lawrence, and R. D. Parks, Phys. Rev. B 16, 2225 (1977). Citing Literature Volume98, Issue21 April 1980Pages K171-K174 ReferencesRelatedInformation

The phonon dispersion curves in symmetry directions of CeD2.12 and CeD2.72 were measured using the inelastic neutron-scattering technique. In both cases the characteristic features of the experimental results can be described satisfactorily by Born-von Kármán tensor force models involving 21 and 28 parameters respectively. In CeD2.72 long-range D-D tensor forces play an important role. In CeD2.72 it was found that the additional deuterium is tightly bound in the lattice and markedly affects the Ce-Ce interactions.

AbstractThe energy distributions of neutrons scattered by α‐MnSeO4, α‐FeSO4, and β‐FeSO4 in their paramagnetic state are measured by means of a time‐of‐flight technique. The values of two exchange parameters can be estimated from a simultaneous analysis of the second moment of these energy distributions and of the Néel temperature computed in the Green's function approximation. Various two‐parameter analyses are performed and checked by comparing calculated and experimental values for θ and χ(TN). For α‐FeSO4 the dominant interactions occur between the first and second neighbours. For β‐FeSO4 two‐parameter analyses do not lead to a satisfactory description of all data; however, one can conclude that the interactions between third neighbours are important, in agreement with the stability conditions for the observed spin configuration.

AbstractThe energy distributions of neutrons scattered by α‐MnSO4 and β‐MnSeO4 in their paramagnetic state are measured by means of a time‐of‐flight technique. From a simultaneous analysis of the second moment of these energy distributions and of the Néel temperature computed in the Green's function approximation it is concluded that the exchange interactions between fourth neighbours play an important role in these manganese compounds. Values for J1 and J4 are obtained from which reasonable values for Θ and χ(TN) are predicted in the case of α‐MnSO4.

Clathrate hydrates are inclusion compounds in which guest molecules are encaged by a H2O host lattice. A structure has been found in the inelastic part of the energy spectra of neutrons scattered by ethylene oxide clathrate deuterate at 30 K. After transformation to effective frequency distributions, three peaks are clearly visible and two possible assignments to librations of the ethylene oxide guest molecules around their principal axes (z being the polar axis) are given.

We have studied the molecular motions of SiH4 by the neutron scattering technique both in the plastic phase I above 63.45 K as well as in phase II. In the plastic phase the spectra are characterized by a very broad quasielastic component. From the Q-behaviour of the quasielastic and elastic intensities and from lineshape fits we have found that a model involving random 120°-reorientations around the threefold molecular axes is able to describe our results satisfactorily. We have derived the residence times and an activation energy of (1.05 ± 0.25) kJ mol-1. In phase II the spectra are characterized by a structure in the inelastic region. The peaks have to be assigned to periodic motions; we conclude that translational and librational modes are separated, with perhaps an overlap at ∽ 12 meV.

physica status solidi (b)Volume 70, Issue 1 p. K69-K72 Short Note Exchange Integral in Normal Spinels with only A-A Interactions D. Scheerlinck, D. Scheerlinck Solid State Physics Department, S. C. K./C. E. N., Mol WONL, Rijksuniversiteit Gent.Search for more papers by this authorS. Hautecler, S. Hautecler Neutron Physics Department, S. C. K./C. E. N., MolSearch for more papers by this authorW. Wegener, W. Wegener Neutron Physics Department, S. C. K./C. E. N., MolSearch for more papers by this author D. Scheerlinck, D. Scheerlinck Solid State Physics Department, S. C. K./C. E. N., Mol WONL, Rijksuniversiteit Gent.Search for more papers by this authorS. Hautecler, S. Hautecler Neutron Physics Department, S. C. K./C. E. N., MolSearch for more papers by this authorW. Wegener, W. Wegener Neutron Physics Department, S. C. K./C. E. N., MolSearch for more papers by this author First published: 1 July 1975 https://doi.org/10.1002/pssb.2220700160Citations: 3 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume70, Issue11 July 1975Pages K69-K72 RelatedInformation

AbstractThe energy distributions of neutrons scattered by Co3O4 in its paramagnetic state have been measured by means of a time‐of‐flight technique. In this normal spinel with only A‐A interactions, the JAA exchange integral has been derived from the second moment of these energy distributions. The result, JAA/kB = (7.27 ± 0.25) K, has been compared with values deduced from an analysis of the macroscopic magnetic data.

The room-temperature spin wave spectrum in MnFe2O4 has been investigated by means of inelastic neutron scattering using the time-of-flight technique. The acoustical branch could be obtained in the [100]- and the [110]-directions up to nearly the Brillouin zone boundary. Values for the effective exchange parameters JAB and JBB have been derived. In both symmetry directions some low lying phonon branches could also be observed.

The room-temperature spin wave spectrum has been investigated in Mn1.7Fe1.3O4 by means of inelastic neutron scattering. The acoustical branch could be obtained in the symmetry directions. Values for the effective exchange parameters JAR and JRR have been derived. Some acoustical phonon branches could also be observed and the elastic constants C44 and (C11 – C12) were estimated.