Neutron scattering demonstrates the coexistence of antiferromagnetic order and superconductivity below 1 K in heavy-electron system ${\mathrm{URu}}_{2}$${\mathrm{Si}}_{2}$. It is found that upper (17.5 K) transition to an phase with a (100) modulation wave vector spins along tetragonal c-axis. The ordered moment unusually small, (0.03\ifmmode\pm\else\textpm\fi{}0.01)${\mathrm{\ensuremath{\mu}}}_{\mathrm{B}}$. However, spin waves develop from damped, finite-gap excitations above...

Neutron scattering has shown that the lowest spin excitations in spin-1 antiferromagnet ${\mathrm{CsNiCl}}_{3}$ its one-dimensional phase occur at finite frequency. After allowance for known weak interchain coupling gap is found to be good agreement with recent numerical calculations. The results support Haldane conjecture integral-spin chains isotropic interactions a separates ground state from excitations.

Antiferromagnetic order and fluctuations in the heavy-fermion superconductor ${\mathrm{URu}}_{2}$${\mathrm{Si}}_{2}$ have been studied by magnetic neutron scattering. Below ${\mathit{T}}_{\mathit{N}}$=17.5 K, is a type-I antiferromagnet with an anomalously small ordered moment of (0.04\ifmmode\pm\else\textpm\fi{}0.01)${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$ polarized along tetragonal c axis. Dispersive resonant excitations exist state zone-center gap 0.43 THz. The are large dipolar matrix...

The introduction of a low concentration defects into magnetic insulator modifies the spectrum excitations. In general consists set impurity modes associated with defect and its immediate neighbors. Impurity that occur outside band host excitations are localized in neighborhood at same time perturb band, while lying within lead to resonant behavior host. recent years, optical, neutron scattering, nuclear resonance techniques have been used study mixed crystals antiferromagnetic transition...

A full description of a series spin-wave measurements in ${\mathrm{CsNiCl}}_{3}$ the three-dimensional (3D) and one-dimensional (1D) phases their analysis to provide first experimental evidence for Haldane gap is presented. Neutron scattering experiments were performed on single crystal with both (h,0,l) (h,h,l) as plane. The order parameter 3D was measured dispersion determined lower phase. spectrum calculated from dynamic susceptibility method compared response phase obtain following...

We have investigated the spin fluctuations at energy transfers up to ~110 meV, well above resonance (33 meV) in YBa2Cu3O6.5 ortho-II superconductor using neutron time-of-flight and triple-axis techniques. The spectrum high energies differs from low-energy incommensurate modulations previously reported where wave vector is largely independent of energy. Well peak response lies vectors that increase with Within error excitations all are best described by a ring around (pi, pi) position....

Inelastic neutron scattering measurements of individual phonon lifetimes and dispersion at 295 1200 K have been used to probe anharmonicity thermal conductivity in $\mathrm{U}{\mathrm{O}}_{2}$. They show that longitudinal optic modes carry the largest amount heat, contrast past simulations total demonstrates a quantitative correspondence between microscopic macroscopic physics. We further performed first-principles for $\mathrm{U}{\mathrm{O}}_{2}$ showing semiquantitative agreement with K,...

The temperature dependence of the positron annihilation peak coincidence rate has been measured in iron from 20 degrees C to 1320 C. did not change across ferro-para magnetic transition at approximately 770 but decreases by 1.5% alpha - gamma phase 910 trapping model analysis data yields values vacancy formation energies (Ef) 1.4+or-0.1 eV -Fe and 1.7+or-0.2 -Fe. correlation between Ef Tt, where Tt is threshold temperature, derived model.

For Pt. I see ibid. vol. 4, 2127. The theory of the low lying magnetic excitations KCoF3 is developed and parameters describing interactions are obtained by comparison with experimental results previous paper. branch elementary excitation spectrum lowest frequency well described a phenomenological model an effective spin s'=1/2. exchange interaction has Heisenberg form, pseudo-dipolar form anisotropic proposed for shown to be less than 8% isotropic exchange. A which takes orbital angular...

The low-lying phonon and magnetic excitations of CoO have been studied experimentally theoretically, both above below the antiferromagnetic ordering temperature. experiments were performed using technique inelastic scattering slow neutrons with aid a triple-axis crystal spectrometer. These difficult because very similar frequencies, also specimen has domain structure in phase. Nevertheless, models obtained for spectra. spectra paramagnetic phase can be understood if spin-orbit coupling...

We describe the relation between spin fluctuations and superconductivity in a highly ordered sample of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.5}$ using both polarized unpolarized neutron inelastic scattering. The susceptibility superconducting phase exhibits one-dimensional incommensurate modulations at low energies, consistent with hydrodynamic stripes. With increasing energy curves upward to commensurate, intense, well-defined, asymmetric resonance 33 meV precipitous...

URh_2Ge_2 occupies an extraordinary position among the heavy-electron 122-compounds, by exhibiting a previously unidentified form of magnetic correlations at low temperatures, instead usual antiferromagnetism. Here we present new results ac and dc susceptibilities, specific heat neutron diffraction on single-crystalline as-grown URh_2Ge_2. These data clearly indicate that crystallographic disorder local scale produces spin glass behavior in sample. We therefore conclude is 3D Ising-like,...

X-ray-resonance magnetic scattering has been used to study antiferromagnetic ordering in the small-moment (\ensuremath{\mu}\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\simeq}0.02${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$) heavy-fermion superconductor ${\mathrm{URu}}_{2}$${\mathrm{Si}}_{2}$. The intensity of (003) reflection develops abruptly at ${\mathit{T}}_{\mathit{N}}$\ensuremath{\simeq}17 K and grows linearly T=3 K, where it saturates. Long-range order...

Neutron scattering from a high-quality single crystal of the heavy-fermion superconductor ${\mathrm{URu}}_{2}$${\mathrm{Si}}_{2}$ has shown onset small, antiferromagnetic ordered moment (0.037${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$) occurs abruptly at ${\mathit{T}}_{\mathit{N}}$, unlike gradual in previously studied samples. The results are good agreement with x-ray-resonance magnetic scattering. magnitude and excitation spectrum same as observed, including anomalous damping excitations...

The crystal structures of the intercalation compounds Li x TiS 2 are investigated by neutron diffraction for = 0.12, 0.33, 0.67, and 1.0. atoms shown to preferentially occupy octahedral sites in van der Waals gaps host lattice all values no evidence three-dimensional ordering is observed.

A theory has been developed of the temperature dependence spin waves in a system involving transitions between all levels ground multiplet an ion. The excitations out both and excited states are described by product annihilation creation operators for single-ion crystalline field molecular field. spin-waves obtained with random-phase approximation applied to interlevel transition rather than ${S}_{z}$ as conventional spin-wave theory. Numerical results have ${\mathrm{Pr}}_{3}$Tl that agree...

Phonons in sodium fluoride have been studied at room temperature using inelastic neutron scattering techniques. Consistent results were obtained a cold time-of-flight apparatus and triple-axis spectrometer. The interpolated on to symmetry directions from the observed surfaces. frequencies units of ${10}^{12}$ ${\mathrm{sec}}^{\ensuremath{-}1}$ some typical phonons are: TA(0,0,1), $\ensuremath{\nu}=4.39\ifmmode\pm\else\textpm\fi{}0.04$; LO(0,0,0.984),...

The ferroelectric transition in K${\mathrm{D}}_{2}$P${\mathrm{O}}_{4}$ has been investigated both experimentally and theoretically. Coherent neutron scattering by fluctuations associated with the was studied above below temperature. None of optic-phonon modes found to change frequency near Curie temperature, contrast materials such as SrTi${\mathrm{O}}_{3}$. gave rise quasi-elastic scattering, increasing intensity approached. distribution showed that pattern displacement atoms these similar...

Antiferromagnetic spin fluctuations in superconducting ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6+\mathrm{x}}$ have been studied using inelastic neutron scattering. In a crystal with x=0.5 and ${T}_{c}$=50 K, we observed at 12 K having cross section which increases increasing excitation energy. The data are consistent highly overdamped waves very short spin-spin correlation length.

Ultraviolet and x-ray-photoelectron spectra of core valence levels in U metal, UN, U${\mathrm{O}}_{2}$, Th, ThN have been obtained. These demonstrate the existence uranium nitride a sharp band $f$ states (containing 2.2\ifmmode\pm\else\textpm\fi{}0.5 electrons) at Fermi level. The anomalously broad $4f$ UN are discussed terms several possible energy-loss mechanisms, including configuration interaction alternating valency. No change is seen density on cooling through antiferromagnetic transition.

The spin-wave response of the $S=\frac{1}{2}$ Ising-like antiferromagnetic chain compounds CsCo${\mathrm{Br}}_{3}$ and CsCo${\mathrm{Cl}}_{3}$ has been studied by inelastic neutron scattering. asymmetry at low temperatures line shape continuum is not correctly predicted existing theory isolated chains to first order in transverse exchange interaction. effective spin Hamiltonian for a rederived shown include slow internal staggered field from mixing that influences rapid fluctuations....