Search results for "Diffraction"
showing 10 items of 1584 documents
Structural and Magnetic Properties of Co-Fe Binary Alloy Monolayers on W(110)
2003
We present an experimental investigation of ${\mathrm{C}\mathrm{o}}_{x}{\mathrm{F}\mathrm{e}}_{1\ensuremath{-}x}$ monolayers grown on flat and stepped W(110) surfaces. Atomically resolved scanning tunneling microscopy and low energy electron diffraction reveal continuous miscibility and pseudomorphic growth of Co and Fe for $0\ensuremath{\le}xl0.6$. We observe short range ordered ${\mathrm{C}\mathrm{o}\mathrm{F}\mathrm{e}}_{3}$-$p(2\ifmmode\times\else\texttimes\fi{}2)$ and CoFe-$c(2\ifmmode\times\else\texttimes\fi{}2)$ structures in the pseudomorphic monolayer. High Co concentrations lead to a phase separation. The Curie temperature and the ferromagnetic Kerr signal at low temperatures decr…
X-ray-diffraction study of the crystal structures and orientational glass state ofAr1−x(N2)xsolid solutions
1990
Solid solutions of ${\mathrm{Ar}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$(${\mathrm{N}}_{2}$${)}_{\mathit{x}}$ have been investigated by x-ray powder diffraction in the range 0.5x1.0, 8T60 K, and under hydrostatic pressures up to 2200 bars. The structural hcp-cubic (Pa3) phase transition is identified as a martensitic transformation with a wide transformation hysteresis. For x0.8 and T30 K the solid solutions show the orientational glass state, which is characterized by a superposition of inhomogeneous and homogeneous lattice strains. The inhomogeneous component is described by the random-field model. The homogeneous component corresponds to an orthorhombic distortion of the hcp lattice. Two …
Spin-polarized Low Energy Electron Diffraction
2007
We review recent progress in the understanding of the physics of ultrathin ferromagnetic films and surfaces that has been made using elastic spin-polarized low-energy electron diffraction (SPLEED). Further development of the experimental technique including high efficient electron sources, spin manipulation and imaging allows a wide range of applications. We report on a quantitative comparison of relativistic dynamical scattering calculations with SPLEED experiments on Fe(110) surfaces and Fe(100)/W(100) thin films leading to an understanding of the spatial distribution of spin densities. Exploiting the surface sensitivity in combination with the large asymmetry of SPLEED, it becomes feasib…
Ultrafast Metamorphosis of a Complex Charge Density Wave in Tantalumdiselenite
2016
Using ultrafast electron diffraction, we record the transformation between a nearly-commensurate and an incommensurate charge-density-wave in 1T-TaS2, which takes place orders of magnitude faster than previously observed for commensurate-to-incommensurate transitions.
Double Bragg Interferometry.
2015
We employ light-induced double Bragg diffraction of delta-kick collimated Bose-Einstein condensates to create three symmetric Mach-Zehnder interferometers. They rely on (i) first-order, (ii) two successive first-order, and (iii) second-order processes which demonstrate the scalability of the corresponding momentum transfer. With respect to devices based on conventional Bragg scattering, these symmetric interferometers double the scale factor and feature a better suppression of noise and systematic uncertainties intrinsic to the diffraction process. Moreover, we utilize these interferometers as tiltmeters for monitoring their inclination with respect to gravity.
Ultrafast Metamorphosis of a Complex Charge-Density Wave
2015
Modulated phases, commensurate or incommensurate with the host crystal lattice, are ubiquitous in solids. The transition between such phases involves formation and rearrangement of domain walls and is generally slow. Using ultrafast electron diffraction, we directly record the photoinduced transformation between a nearly commensurate and an incommensurate charge-density-wave phase in 1T-TaS(2). The transformation takes place on the picosecond time scale, orders of magnitude faster than previously observed for commensurate-to-incommensurate transitions. The transition speed and mechanism can be linked to the peculiar nanoscale structure of the photoexcited nearly commensurate phase.
Neutron-diffraction study of end-for-end ordering in commensurate submonolayers of carbon monoxide physisorbed on the graphite basal plane
1997
The head-tail (dipolar) ordering in commensurate submonolayer films of carbon monoxide adsorbed on graphite recently observed in heat-capacity measurements for T < 5.18 K has been investigated by neutron diffraction. It will be shown that the experimental results are consistent with an end-for-end ordered commensurate herringbone structure.
Subdiffractive solitons in bose-einstein condensates
2005
We predict the disappearance of diffraction (the increase of the mass) of Bose-Einstein condensates in counter-moving periodic potentials. We demonstrate subdiffractive solitons (stable droplets of the condensate) in the vicinity of this zero diffraction point.
Tunable and reconfigurable microwave filter by use of a Bragg-grating-based acousto-optic superlattice modulator
2005
We present an all-optical novel configuration for implementing multitap transversal filters by use of a broadband source sliced by fiber Bragg grating arrays generated by propagating an acoustic wave along a strong uniform fiber Bragg grating. The tunability and reconfigurability of the microwave filter are demonstrated.
Neutron diffraction studies of the molecular compound [Co 2(bta)]n (H4bta =1,2,4,5-benzenetetracarboxylic acid): In the quest of canted ferromagnetism
2013
The exchange mechanism and magnetic structure of the organic-inorganic layered molecule-based magnet [Co2(bta)]n (1) (H 4bta =1,2,4,5-benzenetetracarboxylic acid) have been investigated through variable-temperature magnetic susceptibility measurements and supported with a series of neutron diffraction experiments. Cryomagnetic studies have shown an antiferromagnetic ordering at a transition temperature of 16 K that is followed by the appearance of a weak ferromagnetism below 11 K. The weak antiferromagnetic interlayer interaction plays an important role in this system in spite of the long interlayer separation. A ferromagnetic ordering is induced by applied magnetic fields greater than 1800…