Sponsors:
|
|
Organized by
the Institute of Experimental Physics, University of Bialystok
Norbert Stüßer
Berlin Neutron Scattering Center, HMI, Germany
Neutron powder diffraction as a tool to determine magnetic structures
-
One of the major applications of neutron diffraction is in the study of magnetic structures. Properties which make thermal neutrons an excellent microscopic probe for magnetic structures in solids are the wavelength being of the order of interatomic distances, the presence of a magnetic moment interacting with unpaired electrons in magnetic atoms, and as an uncharged particles the great penetration depth in material. In particular the use of powder diffraction and a data analysis with the use of the Rietveld technique is a very successful method to solve magnetic structures.
This lecture will present the basics of elastic neutron scattering necessary for the study of the spatial ordering of atoms in solids and the spin structure in magnetic materials. The Rietveld method as a technique to refine a crystal and to determine a magnetic structure will be introduced. The instrumentation needed to collect a diffraction pattern will be presented. Since neutron scattering is quite often a flux limited technique some attention will be given to the optimization of a diffractometer in order to tune the resolution to the needs for collecting a powder pattern suitable for analysis by a Rietveld refinement. We will look to the angular dispersive diffractometer at a reactor source in some detail. Besides the principles of a time of flight diffractometer, a technique specially suitable for pulsed neutron sources, will be briefly adressed.
In the final stage one or two examples will be given to demonstrate how a magnetic structure can be solved from a neutron powder pattern.
|
|
|
