The magnetization, $M(H\ensuremath{\le}30\mathrm{T},0.7\ensuremath{\le}T\ensuremath{\le}300\mathrm{K})$, of $({\mathrm{C}}_{5}{\mathrm{H}}_{12}\mathrm{N}{)}_{2}{\mathrm{CuBr}}_{4}$ has been used to identify this system as an $S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1/2$ Heisenberg two-leg ladder in the strong-coupling limit, ${J}_{\ensuremath{\perp}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}13.3\mathrm{K}$ and...

Four time correlation functions of a Lennard-Jones (LJ) fluid at reduced density ${n}^{\mathrm{*}}$=n${\ensuremath{\sigma}}_{\mathrm{LJ}{}^{3}=0.845}$ and temperature ${T}^{\mathrm{*}}$=${k}_{\mathrm{B}\mathrm{T}/{\ensuremath{\varepsilon}}_{\mathrm{LJ}=1.71}}$ have been determined numerically using molecular dynamics. They were computed as function wave number k for numbers 0\ensuremath{\le}k${\ensuremath{\sigma}}_{\mathrm{LJ}<15}$ times...

The total dynamics structure factor S(k,\ensuremath{\omega}) measured by neutron scattering on a mixture of 80% He and 20% Ne at 39.3 K number density 15.1 ${\mathrm{nm}}^{\mathrm{\ensuremath{-}}3}$ shows clear side peaks or shoulders frequencies \ensuremath{\omega}=${\mathrm{\ensuremath{\omega}}}_{\mathrm{s}}^{(1)}$(k) for wave numbers k up to \ensuremath{\approxeq}15 ${\mathrm{nm}}^{\mathrm{\ensuremath{-}}1}$. $omega sub s sup (1) (k)&gt;ck--- (with c the velocity sound) in agreement with...

The oxo-centred trinuclear complex [Fe3O(O2CPh)6(py)3]ClO4·py and its fully deuteriated analogue have been synthesized. X-Ray crystallography at T = 233 K shows that the has threefold symmetry, space group P63/m. Incoherent inelastic neutron scattering spectra 1.5 however show presence of two inequivalent sets molecules, one a static "isosceles" coupled system, with J values for three metal–metal interactions, other dynamic rapid pseudorotation between equivalent isosceles geometries....

For a dense gas equilibrium mixture of 65 at.% He and 35 Ne at T=39.3 K p=114 bar, we determine from neutron scattering the total dynamic structure factor S(k,\ensuremath{\omega}) as function frequency \ensuremath{\omega} for wave numbers 4k28 ${\mathrm{nm}}^{\mathrm{\ensuremath{-}}1}$. all k, is sum four Lorentzians; two located \ensuremath{\omega}=\ifmmode\pm\else\textpm\fi{}${\mathrm{\ensuremath{\omega}}}_{\mathit{s}}^{(1)}$(k) (directly visible smaller k)...

Resonant x-ray scattering experiments on high-temperature superconductors and related cuprates have revealed the presence of intense paramagnon at high excitation energies, order several hundred meV. The energies appear to show very similar behavior across all compounds, ranging from magnetically ordered, via superconductors, heavy fermion systems. However, we argue that this apparent has been inferred data through model fitting which implicitly imposes such similarities. Using is free...

Catena(dimethylammonium-bis(mu2-chloro)-chlorocuprate), (CH3)2NH2CuCl3, forms chains of Cu2Cl6(2-) bifold dimers linked along the structural chain axis by terminal chlorides forming long semicoordinate bonds to adjacent dimers. The are separated dimethylammonium ions that hydrogen bond chloride A phase transition below room temperature removes disorder in bonding, leaving structurally and magnetically inequivalent, with alternating ferromagnetic antiferromagnetic pairs. coupled isolated from...

Magnetite (Fe3O4) is a mixed valent system where electronic conductivity occurs on the B site (octahedral) iron sublattice of spinel structure. Below T(V)=123 K, metal-insulator transition which argued to arise from charge ordering 2+ and 3+ valences sites (Verwey transition). Inelastic neutron scattering measurements show that optical spin waves propagating (approximately 80 meV) are shifted upwards in energy above T_{V} due occurrence B-B ferromagnetic double exchange phase. The...

A thorough analysis of the transverse current autocorrelation function obtained by molecular dynamics simulations a dense Lennard-Jones fluid reveals that even such simple system is characterized varied dynamical behavior with changing length scale. By using exponential expansion theory, we provide full account time correlation at wavevectors Q between upper boundary hydrodynamic region and Q_{p}/2, Q_{p} being position main peak static structure factor. In range studied, identify accurately...

We present inelastic neutron scattering experiments, performed near the antiferromagnetic quantum critical point in Ce(Ru0.24Fe0.76)2Ge2. Both local and long-range fluctuations of moments are observed, but due to Kondo effect only latter critical. propose a phenomenological expression which fits energy E, temperature T, wave vector q dependences dynamic susceptibility, describing non-Fermi liquid E/T scaling found at every q.

Inelastic neutron scattering results on magnetite $({\mathrm{Fe}}_{3}{\mathrm{O}}_{4})$ show a large splitting in the acoustic spin wave branch, producing $7\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ gap midway to Brillouin zone boundary at $\mathbf{q}=(0,0,1∕2)$ and $\ensuremath{\hbar}\ensuremath{\omega}=43\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$. The occurs below Verwey transition temperature, where metal-insulator simultaneously with structural transformation, supposedly caused by charge...

Magnetic ordering has been investigated by means of neutron scattering in an $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6+x}$ single crystal prepared with two different oxygen concentrations, $x=0.1$ and $x=0.18$, aluminum-doped $\mathrm{Y}{\mathrm{Ba}}_{2}({\mathrm{Cu}}_{3\ensuremath{-}y}{\mathrm{Al}}_{y}){\mathrm{O}}_{6+x}$ $x=0.25$ $y=0.14$. For the undoped crystal, a magnetic transition was observed at ${T}_{N}=410$ (respectively for $x=0.18$), but no second found down to...

The authors measured the static structure factor S(k) of dense fluid helium by neutron diffraction as a function density (at fixed temperature T=13.3 K) and number n-18.7 nm-3). They give results calculate derivative at K; n=22.0 nm-3. use this derivative, which is determined triplet correlation g3(r,s), to test proposal for g3(r,s) made Winfield Egelstaff. find that proposed form gives reasonable prediction experimental derivative. Hence, they estimate square energy-density equal times,...

We present inelastic neutron scattering measurements on liquid mercury at room temperature for wave numbers q in the range 0.3 <q<7.0 A(-1). find that energy half width of incoherent part dynamic structure factor S(q,E) is determined by a self-diffusion process. The coherent shows characteristic behavior expected cage diffusion also show response function small exhibits quasielastic mode with time scale diffusion, however, its intensity larger an order magnitude than what would be diffusion....

Sillimanite and kyanite are two of the polymorphs aluminum silicate ${\mathrm{Al}}_{2}{\mathrm{SiO}}_{5},$ a geophysically important mineral system. Their crystal structures characterized by chains octahedra linked through aluminum, silicon, oxygen atoms. We report experimental studies phonon densities states sillimanite kyanite, their interpretations based on shell model calculations. The inelastic neutron-scattering experiments were carried out both triple-axis spectrometer at steady state...

We present neutron scattering data on $\mathrm{Ce}{({\mathrm{Ru}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x})}_{2}{\mathrm{Ge}}_{2}$ that show magnetic ordering in the vicinity of a quantum critical point is restricted to short length scales even though all moments are have lined up with their neighbors. argue order not limited by crystallographic defects but rather fluctuations disorder system and dilute such an extent percolation network forms. The latter naturally explains how $E∕T$ scaling...

Using neutron scattering, we determine the dynamic structure factor $S(q,\ensuremath{\nu})$ of liquid ${}^{4}\mathrm{He}$ for roton wave number $q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2.0{\AA{}}^{\ensuremath{-}1}$ as a function frequency $\ensuremath{\nu}$ at constant density $0.1715\mathrm{g}{\mathrm{cm}}^{\ensuremath{-}3}$ and ten temperatures in range $1.08\ensuremath{\le}T\ensuremath{\le}2.00\mathrm{K}$, primarily near superfluid transition temperature...

High-energy-resolution quasielastic neutron scattering on three complementary spectrometers has been used to investigate molecular diffusive motion in solid nano- bulk-sized particles of the alkane n-C32H66. The crystalline-to-plastic and plastic-to-fluid phase transition temperatures are observed decrease as particle size decreases. In all samples, localized plastic occurs two different time scales: a "fast" corresponding uniaxial rotation about long axis; "slow" attributed conformational...

From inelastic neutron scattering we determine the dynamic structure factor $S\left(q,\ensuremath{\omega}\right)$ of fluid helium at 4 K and 1 bar as a function frequency $\ensuremath{\omega}$ for wave numbers $2.5<q<30$ n${\mathrm{m}}^{--1}$. is completely given by only two phonon contributions located sound propagation frequencies $\ifmmode\pm\else\textpm\fi{}{\ensuremath{\omega}}_{s}\left(q\right)$. For $18<q<21$ n${\mathrm{m}}^{--1}$ they are overdamped, i.e.,...

A Monte Carlo algorithm for the analysis of powder diffraction patterns is presented. One aim this algorithm, which can be used as a supplement to regular Rietveld refinement, provide self-consistent determination thermal displacements atoms. This achieved by modelling total scattered intensity, comprising both Bragg peak intensity and diffuse contribution spectrum from scattering density an assembly assembly, constructed reverse technique so yield best fit with data, then calculate average...

The two B-site ions Mn3+ and Mn4+ in the stoichiometric spinel structure LiMn2O4 form a complex, columnar ordered pattern below charge-ordering transition at room temperature. On further cooling to 66 K, system develops long-range antiferromagnetic order. In contrast, whereas lithium-substituted Li[Mn2−xLix]O4 also undergoes around temperature, it only displays frozen short-range magnetic order ∼25–30 K. We investigate what extent charge-order observed can account for measured ordering...

We present neutron scattering results on the magnetic excitations in spinel compounds Li$_x$[Mn$_{1.96}$Li$_{0.04}$]O$_4$ (x= 0.2, 0.6, 0.8, 1.0). show that dominant below T ~ 70 K are determined by clusters of Mn^4+ ions, and these mimic E/T-scaling found quantum critical systems also harbor clusters, such as CeRu$_{0.5}$Fe$_{1.5}$Ge$_2$. argue our for this classical compound unusual response at low temperatures observed is (at least) partially result fragmentation lattice into smaller...