Studies of atomic diffusion in Ni-Pt solid solution by x-ray photon correlation spectroscopy.

Atomic scale x-ray photon correlation spectroscopy (aXPCS) was used to study atomic diffusion in the Ni(97)Pt(3) solid solution with both a single crystal and a polycrystalline sample. Different jump diffusion models are discussed using experimental results and Monte Carlo simulations. The sensitivity of aXPCS experiments to short-range order (in this case governed by a strong Pt-Pt repulsive force) is demonstrated.

Study of reorientation processes in L1-ordered FePt thin films.

We report on the development of structural and magnetic order in epitaxially grown L1 FePt thin films. Upon annealing, the easy axis of magnetization changes from the out-of-plain into the in-plain direction. We found that the overall fraction of reoriented domains first increases but after certain time decreases before achieving a saturated state.

Atomic diffusion studied with coherent X-rays.

Knowledge of atomic diffusion is a fundamental issue in synthesis and stability of materials. Direct studies of the elementary diffusion event, that is, how the individual atoms 'jump', are scarce, as the available techniques are limited to selected systems. Here we show how by monitoring the spatial and temporal variations of the scattered coherent X-ray intensity the diffusion of single atoms can be studied.

Vibrational properties of nanograins and interfaces in nanocrystalline materials.

The vibrational dynamics of nanocrystalline Fe(90)Zr(7)B(3) was studied at various phases of crystallization. The density of phonon states (DOS) of the nanograins was separated from that of the interfaces for a wide range of grain sizes and interface thicknesses. The DOS of the nanograins does not vary with their size and down to 2 nm grains still closely resembles that of the bulk.

An ultrahigh vacuum system for in situ studies of thin films and nanostructures by nuclear resonance scattering of synchrotron radiation.

A multifunctional ultrahigh vacuum (UHV) system has been set up at the nuclear resonance beamline ID18 of the European Synchrotron Radiation Facility (ESRF). Thin and ultrathin films, nanoislands and -wires, multilayers, and stoichiometric oxides can be prepared by molecular beam epitaxy and characterized by low-energy electron diffraction, Auger electron spectroscopy, and reflection high-energy electron diffraction. Upon characterization the sample is transferred under UHV conditions to the chamber for experiments with the synchrotron beam.