Search

Neutron scattering is used for examining the layered A-type antiferromagnet Pr0.5Sr0.5MnO3. A gap of 2.3 plusminus 0.2 meV at the zone center [0.5 0 0.5] is observed in the spin-wave excitations.

Elastic neutron scattering is used to examine the peculiar structure of charge and spin ordering in the half-doped layered perovskite oxide La1.5Sr0.5CoO4. The spin structure is a damped flat spiral polarized in the a-b plane with the propagation vector Q=(zeta, zeta, 1).

Magnetic measurements and neutron diffraction techniques were used for examining the magnetic structure of high purity MnBi low temperature phase. A coercivity of 2.0 T at 400 K and a positive temperature coefficient from 0 to at least 400 K is observed in the low temperature phase of the MnBi alloy.

The direct visualization of deuterium molecules adsorbed on isoreticular metal organic frameworks (IRMOF-1) is presented by using reverse Monte Carlo simulation based on first principle molecular dynamics simulation and neutron diffraction. The studies have shown that the average distance of deuterium molecules adsorbed onto IRMOF-1 is longer than that in a solid state but much shorter than that in the corresponding gas state.

Several studies are conducted to explain the annealing nature of the defects present in the depletion region, as well as the neutral base of the neutron damaged silicon bipolar transistors. The generation/recombination currents exhibited by the base-emitter junctions are shown to be the main factor leading to large, damage-induced base currents.

Numerous microcompression experiments are conducted to explain the analyze the stress-induced transformation taking place in the single crystal micron-scaled NiTi micropillars. The elastic deformation of the compounds is shown to be highly dependent on the orientation.

The small and ultrasmall angle neutron scattering (SANS/USANS) measurements are used for the internal void morphology of the high explosive RDX. The neutron scattering invariant calculated over the measured SANS and USANS has tracked well with sensitivity testing of the materials.

Several analyses are conducted to explain the magnetic structure, as well as the magnetic entropy changes taking place in the intermetallic polycrystalline compound, DyCoAl. The collinear ferromagnetic structure exhibited by the compounds is also analyzed.

A combination of the small-angle neutron scattering and polarization analysis techniques is employed to explain the internal magnetic structure of the various magnetic nanoparticles. The intrinsic magnetic morphology exhibited by the nanoparticles is also analyzed.

A combination of the small-angle neutron scattering and Kerr microscopy techniques is employed to explain the origin of large magnetostriction in the Fe-Ga alloys. The magnetostriction observed in the alloys is shown to be completely dependent on the different nanoclusters.

The recording neutron powder diffraction technique is employed to explain the structure and the magnetic properties of the La[Mn.sub.1- x][Cu.sub.x][O.sub.3] (x = 0.05, 0.10 and 0.15) samples. The spin canting phenomenon exhibited by the system is also analyzed.

The article presents a new technique, which can be used for explaining the propagation of volume magnetization taking place in the bulk ferromagnetic materials. The image obtained from the technique is shown to be extremely accurate and is called the neutron dark-field image.

The combination of a simple bilayer model with Fourier synthesis has led to a robust estimation of the bilayer thickness. The studies have shown that even a simple mathematics means to two and three peak diffraction pattern can be utilized.

Neutron diffraction is used for examining the crack-growth retardation phenomenon after a single tensile overload by mapping both one-dimensional and two-dimensional residual-strain distributions around the crack tip in a series of compact-tension specimens representing various crack-growth stages through an overload-induced retardation period. The relationship between the overload-induced plastic zone and subsequent fatigue-induced plastic zone and its impact on the residual-strain distributions in the perturbed plastic zone are explored.

Atomistic kinetic Monte Carlo simulations based on the two-band semiempirical cohesive model for Fe-Cr which revealed a body centered tetragonal [Fe.sub.14]Cr ordered compound at very low temperature is reported. The results suggested the possible presence of a large spectrum of correlation lengths in the experimental alloy and an [alpha]-phase short-range ordered in the two-phase region.

Polarized small-angle neutron scattering is used for measuring the local magnetic structure of writable thin-film perpendicular media with a granular CoCrPt-Si[O.sub.x] recording layer. The analytical and numerical approach based on transmission electron microscopy measurements of the grains have shown that the recording layer has fermomagnetically ordered core regions that are smaller in extent than the corresponding grains and have allowed a direct comparison of these two length scales.

Small angle neutron scattering measurements are used for examining the mesoscopic structure of a variety of potteries of relevance to cultural heritage coming from different Sicilian (Southern Italy) archeological sites belonging to the 'Strait of Messina' area. The data are compared with the mesoscopic parameters extracted for two series of clayey sediments of the Strait of Messina area and fired under controlled conditions.

Neutron diffraction and pair distribution function analysis (PDF) are used for examining the most important family of proton conducting oxides, cerates. The structural effects of Y-doping and water incorporation in cerates proton conductors are described from a viewpoint of the average structure and the local structure.

Time-of-flight neutron powder diffraction and specific heat measurements were employed to study the nature of thermal expansion in rhenium trioxide, an electrically conducting oxide with cubic symmetry. The temperature evolution of the lattice parameters indicated that Re[O.sub.3] could exhibit negative thermal expansion below room temperature and that the transition from negative to positive thermal expansion depended on sample preparation.

Combination of x-ray and neutron diffraction, magnetic measurements, and iron-57 Mossbauer spectroscopy are employed to study the Tb[Co.sub.4-x][Fe.sub.x]B compounds with x=0, 1, and 2. The compensation temperature of the Tb[Co.sub.4-x][Fe.sub.x]B compounds decreased continuously from 400 to 350 K between x=0 and 2 as a result of an iron induced increase in the transition metal magnetization.

Neutron diffraction data are collected from sintered from polycrystalline 0.9BiFe[O.sub.3]-0.1PbTi[O.sub.3] at temperatures between 293 and 793 K and the crystal and magnetic structures refined by the Rietveld method. A maximum in the spontaneous rhombohedral strain is seen close to the Neel temperature, which is different from Landau behavior for a ferroelectric and has suggested a coupling between the magnetic and nuclear structures.

Magnetization, x-ray diffraction, and neutron diffraction studies were performed to determinet the influence of Ca ion substitution on the structural and superconducting properties of ([Nd.sub.1-x][Ca.sub.x])([Ba.sub.1.6][La.sub.0.4])[Cu.sub.3][O.sub,.z] system (where x=0.0-0.6). The intermixing of Ca and La sites randomized the chain site oxygens to yield a tetragonal structure despite an oxygen content close to 7.0 for all the Ca doped samples and on further increase in Ca content resulted in the change of coordination from sixfold to eightfold at x >= 0.4.

Order-disorder phase transitions in magnetic metals occurring at zero temperature are analyzed. The studies have shown how the disorder has introduced a change in morphology from a three-dimensional system to a collection of magnetic clusters and neutron scattering data is presented for a classical system, Li[[Mn.sub.1.96][Li.sub0.04]][O.sub.4], that has shown how magnetic clusters by themselves can lead to scaling laws that mimic those seen in quantum critical systems.

The re-entrant spiral magnetic order and ferroelectricity is observed below 6 K in [Mn.sub.0.965][Fe.sub.0.035]W[O.sub.4] under applied magnetic fields above 3.6 T. The re-entrant magnetic/ferroelectric phase behavior is studied by single crystal neutron scattering and the H-T phase diagram is resolved from neutron, dielectric constant, polarization and magnetic measurements.

The temperature dependence of the structural parameters and the occurrence of magnetism in UPdSn and UCuSn are measured by using neutron diffraction. Rietveld refinement of neutron diffraction data is used for determining the shortest interatomic distances for temperatures between 15 K and room temperature and the changes in the interatomic distances have caused changes in the hybridization effects, leading to the formation of a magnetic ground state for both compounds.

The structural characterization of new nanocomposites by small angle x-ray scattering (SAXS) and small angle neutron scattering is described for evaluating interparticle separation in two types of assemblies, three dimensional periodic arrays and disordered assemblies. The magnetic behaviors of the two systems are distinctly different and the main structural factor contributing to the differences in magnetic properties is likely to be the array order.

Magnetometry and neutron scattering are used for analyzing the magnetic properties of pressure-graded Co/Pd multilayers. Complementary magnetometry results have shown that the graded magnetic profiles are because of a decrease in saturation magnetization for regions deposited at higher pressure and the increased deposition pressure has shown increased coercivity.

Neutron reflectometry is used for analyzing the formation and evolution of magnetic domains within a patterned array of NiFe/Cu/Co ellipses. The studies have shown that there is one magnetic domain per nanoparticle whose constituent moments rotate collectively as the field is varied.

Neutron scattering experiments using a two-dimensional detector are used for measuring a nuclear Bragg peak and its six surrounding magnetic satellites in (110)europium film. The thermal history of the film has dramatic consequences on the magnetic configurations, correlated with lattice clamping effects persisting above the magnetic ordering temperature.

Magnetization and neutron diffraction studies are carried out on a polycrystalline [Tb.sub.2][Ti.sub.3][Ge.sub.4] sample. Neutron powder diffraction data has confirmed the existence of a magnetic long range order and the modeling of the magnetic scattering has disclosed a complex and incommensurate antiferromagnetic spin structure below [T.sub.N].

Neutron diffraction patterns are acquired in situ from a melt-spun amorphous [Fe.sub.74][Nd.sub.5][B.sub.18][Cr.sub.3] alloy upon rapid thermal annealing at constant rates. The heterogeneous nucleation of [Nd.sub.2][Fe.sub.14]B on tetragonal-[Fe.sub.3]B precipitates promoted by the 3d transition-metal additives is used for magnetic hardening.

In situ neutron powder diffraction is used for the formation of the ordered [L1.sub.0] structure from the A1 phase in nanocrystalline [Fe.sub.100-x][Pd.sub.x] and [Co.sub.100-x][Pt.sub.x] alloys. The magnetic moment of iron in the [L1.sub.0] FePd phase has decreased with increasing Fe concentration and in the Co-Pt alloys the Co magnetic moment is independent of the composition and degree of chemical order.

Polarized neutron reflectometry and magnetization measurements are used for studying the magnetization reversal in magnetron sputtered CoPt(111) hard/soft bilayers. All the samples have shown the same features in their first order reversal curves but the lateral domain size during the magnetization reversal of the soft layer has differed and the hard layer reversal has occurred through the reorientation in small domains.

The crystal structure of the sol-gel derived pyrochlore [Bi.sub.2][Ti.sub.2][O.sub.7] is refined by a Rietveld analysis method by using both neutron scattering and x-ray diffraction data. The measured electrical properties of the sol-gel [Bi.sub.2][Ti.sub.2][O.sub.7] thin film has displayed a ferroelectricity evident from the measured electric field dependent polarization and the ferroelectricity of the [Bi.sub.2][Ti.sub.2][O.sub.7] thin film is attributed by Bi atoms occupying 96g site.

The spatial correlation of polarization under the impact of boundary conditions on electrodes of the capacitor and 'dead layer' model are used for modeling the size effect in a ferroelectric parallel plate capacitor. The size effect and definitions of the dead layer parameters are based on the correlation of the dynamic ferroelectric polarization in conjunction with the relevant boundary conditions.

(1-x)PbTi[O.sub.3]-xBi([Zn.sub.1/2][Ti.sub.1/2])[O.sub.3] solid solutions have shown an enhanced tetragonality (c/a) and Curie temperature and its structure is studied by using neutron powder diffraction based on the Rietveld refinement. The ceramic of (1-x)PbTi[O.sub.3]-xBi([Zn.sub.1/2][Ti.sub.1/2])[O.sub.3] (x = 0.3) has displayed a low dielectric loss due to the [d.sup.0] electronic structure.

The magnetic [super 57]Fe Mossbauer effect and neutron diffraction measurements are used to study the magnetic properties and magnetic structures of Pr[Mn.sub.2-x][Fe.sub.x][Ge.sub.2] compounds. The results showed that the interlayer Mn-Mn interactions play a significant role in the anomalous thermal expansion observed at magnetic transition in the layered system, and hence also in controlling the magnetovolume effects.

In situ time-of-flight neutron diffraction and high-energy x-ray diffraction techniques are used to gain insight into the principles of the detwinning mechanism under a uniaxial loading of Ni-Mn-Ga ferromagnetic shape memory alloys (SMAs). The direct observations for the detwinning process of variants have provided better understanding for the deformation mechanisms in SMAs used as sensors and actuators.

High oxygen pressure methods are used for preparing two ferromagnetic compounds of the series La([Cu.sub.3-x][Mn.sub.x])[Mn.sub.4][O.sub.12] (x=1 and x=2). The magnetic moments of the [Mn.sup.6b.sup.3+] ions are partially polarized in the line of the magnetic moments of [Mn.sub.8c], leading to parallel alignment at the different sublattices by neutron powder diffraction (NPD) methods for x=1, x=2.

Inelastic neutron scattering and magnetization measurements are used for studying the magnetism of two cuprates on powder samples. The spin system is determined as a spin-1/2 twofold-period (alternating) antiferromagnetic (AF) chain with two exchange interaction values and [Cu.sub.3][([P.sub.2][O.sub.6]OD).sub.2] has a spin-1/2 threefold-period quantum antiferromagnetic chains.

The magnetic structure of the first field-induced phase (FM-[I.sub.111]) is determined by using the neutron diffraction by using a single crystal of DyCu under various magnetic fields. The interaction energies in the antiferromagnetic and FM-[I.sub.111] phases are shown to be comparable.

The diamagnetic-paramagnetic and insulator-metal transitions in LnCo[O.sub.3] perovskites (Ln=La, Y, rare earths) are studied and modeled as a two-level excitation process. The model parameters are quantified for Ln=La, Pr, and Nd samples by using the powder neutron diffraction on the thermal expansion of Co-O bonds that is associated with the two successive spin transitions.

High-resolution neutron diffraction patterns are used for studying the melt-spun Fe-Ga ribbons. They have identified the [D0.sub.3] phase and have confirmed the existence of possible short range ordering.

The depth-dependent magnetic structure of a EuO magnetic tunnel junction having a Gd electrode, Si/Cu/EuO/Gd/Al, is analyzed by using polarized neutron reflectometry. The differences of the structural and magnetic behavior of the Gd layer relative to bulk in vital in optimizing the tunnel magnetoresistance in these samples.

A comparative study of PrBa[Co.sub.2][O.sub.5.50] and YBa[Co.sub.2][O.sub.5.50] is described. High temperature magnetic measurements have shown different spin states of Co ions in both compounds and neutron powder diffraction below room temperature have shown a different succession of magnetic arrangements.

The effects of Cu-doping on the structural, magnetic, and transport properties of La(sub 0.7)Sr(sub 0.3)Mn(sub 1-x)Cu(sub x)O3 are studied using neutron diffraction, magnetization, and magnetoresistance measurements. All samples show the rhombohedral structure with the R3c space-group from 10 K to room temperature.

High resolution neutron powder diffraction, ac-susceptibility and (super 166)Er Mossbauer spectroscopy were used for determining the magnetic structure of Er5Si4. 32(3) K is the magnetic ordering temperature of Er5Si4 and its magnetic structure is characterized by ferromagnetic order of three Er sites (4c, 8d1 and 8d2) along [010] with antiferromagentic order of the 8d sites in the perpendicular (010) plane.

A unifying, rigorous treatment is given for the diffraction stress analysis of both macroscopically elastically isotropic specimens and macroscopically elastically anisotropic specimens. The notion surface anisotropy of bulk specimens is revisited as a special case of direction-dependent grain interaction.