Neutron Diffraction: A tool for the Magnetic Properties
We start this chapter with an introduction of basic information of nuclear scattering, elastic neutron scattering by polycrystals, magnetic scattering, and some applications of neutrons. In the main part, it has the basic information for determining magnetic structures of any compound through analysis from neutron powder diffraction data. As an example, we will analyze the data collected for the double perovskite Sr2Y RuO6 at variable step in scattering angle 2θ in the D1B instrument/Institut Laue-Langevin (ILL). We collected one pattern in the paramagnetic state (40 K), and we refined the crystal structure using a PCR file. Another pattern, in the magnetic state (1.6 K), was collected in order to observe the magnetic peaks. To analyze the data, we used the FullProf Suite program and other subprograms as WinPLOTR-2006 to select the peaks, K_Search to determine the propagation vector K, and BasIreps to obtain the magnetic structure symmetry of the compound in coefficients of the basis functions and in Cartesian or spherical components. We used the FullProf Studio for visualizing crystal and magnetic structures. Furthermore, we show how to use the Le Bail method to check the propagation vector calculated. For determining the magnetic structure of a material, required from the reader is the minimal experience with crystallography and structure refinement using X-ray powder diffraction and/or neutron diffraction through Rietveld analysis.
This research was supported by the Brazilian agencies CNPq and CAPES. Research at Institut Laue-Langevin, D1B (CRG) – High resolution neutron two-axis powder diffractometer – was sponsored by the Scientific User Facilities Division, European scientific research organizations. We would like to thank Dr. Claire Colin (ILL) for the assistance with NPD measurements and Dr. John Neumeier (MSU–USA), Dr. Luis Ghivelder, and Dr. Sergio Garcia (UFRJ–Brazil) for the assistance with sample synthesis.
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