The influence of twin boundaries on the Flux Line Lattice structure in YBaCuO: a study by Small Angle Neutron Scattering

The influence of Twin Boundaries (TB) on the Flux Line Lattice(FLL) structure was investigated by Small Angle Neutron Scattering (SANS). YBaCuO single crystals possessing different TB densities were studied. The SANS experiments show that the TB strongly modify the structure of the FLL. The flux lines meander as soon as the magnetic field makes an angle with the TB direction. According to the value of this angle but also to the ratio of the flux lines density over the TB density, one observes that the FLL exhibits two different unit cells in the plane perpendicular to the magnetic field. One is the classical hexagonal and anisotropic cell while the other is affected by an additional deformation induced by the TB. We discuss a possible relation between this deformation and the increase of the critical current usually observed in heavily twinned samples.Comment: accepted for publication in Phys Rev

Sample positioning in neutron diffraction experiments using a multi-material fiducial marker

An alternative sample positioning method is reported for use in conjunction with sample positioning and experiment planning software systems deployed on some neutron diffraction strain scanners. In this approach, the spherical fiducial markers and location trackers used with optical metrology hardware are replaced with a specifically designed multi-material fiducial marker that requires one diffraction measurement. In a blind setting, the marker position can be determined within an accuracy of ±164 µm with respect to the instrument gauge volume. The scheme is based on a pre-determined relationship that links the diffracted peak intensity to the absolute positioning of the fiducial marker with respect to the instrument gauge volume. Two methods for establishing the linking relationship are presented, respectively based on fitting multi-dimensional quadratic functions and a cross-correlation artificial neural network

The development and applications of ultrafast electron nanocrystallography

We review the development of ultrafast electron nanocrystallography as a method for investigating structural dynamics for nanoscale materials and interfaces. Its sensitivity and resolution are demonstrated in the studies of surface melting of gold nanocrystals, nonequilibrium transformation of graphite into reversible diamond-like intermediates, and molecular scale charge dynamics, showing a versatility for not only determining the structures, but also the charge and energy redistribution at interfaces. A quantitative scheme for three-dimensional retrieval of atomic structures is demonstrated with few-particle (< 1000) sensitivity, establishing this nanocrystallographic method as a tool for directly visualizing dynamics within isolated nanomaterials with atomic scale spatio-temporal resolution.Comment: 33 pages, 17 figures (Review article, 2008 conference of ultrafast electron microscopy conference and ultrafast sciences

Simulacijsko modeliranje rendgenske difrakcije uzoraka piritnog pepela bioprocesiranog u medijima koji sadrže Acetobacter aceti

Phenomenal profiling functions were applied for the simulation of an X-ray diffraction (XRD) pattern of pyrite ash bioprocessed in Acetobacter aceti contained growth media. The full width at half maximum (FWHM) values were estimated for each pattern of pyrite ash, and the Bragg equation was used to determine the atomic layer spacing, as well crystallite size and strain broadening were accomplished by applications of Scherrer and Williamson-Hall equations. Errors in line broadening were correlated with the FWHM equations of the generalised profiling functions, and the microstrain (ε) was estimated with the relation between the integral breadth (βi) and cosθ. Furthermore, the XRD pattern of a discrete peak was 3D simulated using Gaussian, Lorentzian, Pearson VII, pseudo-Voigt, and Voigt functions. The Gaussian function with a round top peak was designated the most suitable profile simulation by offering the maximum peak height, Imax and tails comparable to the experimental peak. This work is licensed under a Creative Commons Attribution 4.0 International License.Fenomenalne funkcije profiliranja primijenjene su za simulaciju rendgenske difrakcije (XRD) uzorka piritnog pepela bioprocesiranog u medijima koji sadrže Acetobacter aceti. Vrijednosti širine linije na polovici visine (FWHM) procijenjene su za svaki uzorak piritnog pepela. Braggova jednadžba primijenjena je za određivanje razmaka atomskog sloja, dok su za veličinu kristalita i širenje deformacija primijenjene Scherrerove i Williamson-Hallove jednadžbe. Pogreške u proširivanju linija povezane su s jednadžbama generaliziranih funkcija profiliranja FWHM, a mikronaprezanje (ε) je procijenjeno odnosom između integralne širine (βi) i cosθ. Nadalje, XRD uzorak diskretnog vrha prikazan je 3D simulacijom primjenom Gaussove, Lorentzianove, Pearsonove VII, pseudo-Voigtove i Voigtove funkcije. Gaussova funkcija s okruglim vrhom pokazala se najprikladnijom simulacijom profila nudeći maksimalnu visinu vrha, Imax i krajeve usporedive s eksperimentalnim vrhom. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna

MAGNETO-OPTICAL PROPERTIES OF THIN PERMALLOY FILMS: A STUDY OF THE MAGNETO-OPTICAL GENERATION OF LIGHT CARRYING ANGULAR MOMENTUM

Magneto-optical materials such as permalloy can be used to create artificial spin- ice (ASI) lattices with antiferromagnetic ordering. Magneto-optical materials used to create diffraction lattices are known to exhibit magnetic scattering at the half- order Bragg peak while in the ground state. The significant drawbacks of studying the magneto-optical generation of OAM using x-rays are cost, time, and access to proper equipment. In this work, it is shown that the possibility of studying OAM and magneto-optical materials in the spectrum of visible light at or around 2 eV is viable. Using spectroscopic ellipsometry it is possible to detect a change in the magnetization of thin permalloy films with thicknesses between 5 and 20 nm. Patterns consistent with OAM were found at 1.95 eV using a square lattice with a 4 radial phase shift in the antiferromagnetic ground state. Evidence of magnetic scattering at the half-order Bragg peak using 1.95 eV was also found