The extreme absorption cross section of natural gadolinium has so far precluded routine neutron diffraction work on its alloys and compounds. However, it is shown here that an easily constructed flat-plate sample holder with silicon single-crystal windows can be used to place a thin layer of material in a neutron beam and obtain Rietveld refinement quality diffraction data in a modest time. The flat-plate geometry uses a large area to compensate for the necessarily thin sample. Demonstration data are presented on two intermetallic compounds, Sm3Ag4Sn4and Gd3Ag4Sn4, and it is shown that both structural and magnetic information can be derived from the diffraction patterns. By working at a wavelength of 2.37 Å, it is possible to observe the low-Qdiffraction peaks associated with magnetic ordering. This simple methodology should now enable routine measurements on even the most highly absorbing materials.
