Electron microscopy
Example of Indexing Electron Diffraction Pattern from Twins
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Figure 3035 shows a [110] L10 (P4/mmm)-FePt crystal, consisting of a (111) twin in fct (face centered tetragonal) phase structure. The reflections connected by the solid and dashed lines originate from twin and matrix, respectively. The extra weak reflections marked by the white arrowheads in Figure 3036 (a) are from chemical ordering in the L10-FePt structure. The twin plane is parallel to (1 -1 -1) or (-1 1 -1)t, where the subscript “t” represents the twin reflection. The c-axes of the twin and matrix are on the same plane and form a mirror symmetry relative to the (1 -1 -1) or (-1 1 -1)t twin plane.

[110] L10 (P4/mmm)-FePt crystal with (111) twin in fct

Figure 3035. (a) HRTEM image of a twin boundary in a L10-FePt crystal with zone axis of [110]. (b) The twin structure model, where the open circles are Fe atoms and the full circles represent Pt atoms. (c) Fast Fourier transform (FFT) of the corresponding image in (a). [1]



[1] Z. R. Dai, Shouheng Sun, and Z. L. Wang, Phase Transformation, Coalescence, and Twinning of Monodisperse FePt Nanocrystals, NANO LETTERS, 1 (8), 443-447, 2001.



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