Electron microscopy of the mineral chalcopyrite, CuFeS₂

The crystal symmetry of the mineral chalcopyrite has been investigated using Kikuchi-line intersections. It has been found that Kikuchi lines which intersect within systematic rows of reflections are very sensitive to small differences in interplanar spacings and can be used for symmetry determination. A small displacement of the point of intersection of the Kikuchi lines 3,3, and 7 within the 02 and 04 systematic row of Kikuchi reflections was seen, indicating that the 02 and 04 Kikuchi lines do not lie on a mirror plane. Similar observations were also made for the intersection points of the , , 10, 32 and , , 14, 52 Kikuchi lines within the 02 and 04 systematic row of reflections. The Kikuchi lines intersecting within the 0h0 systematic rows of reflections showed no displacements, which is consistent with the point group, 2m, of chalcopyrite. The antiferromagnetic superstructure of chalcopyrite has also been investigated. Dark-field transmission electron microscope (TEM) images obtained with the 110 superstructure reflection showed antiferromagnetic domains, which altered their configurations on heating by the electron beam. The alterations were reversible and were interpreted as originating from magneto-elastic deformation.