Oriented Nanomagnets Originating from Topotactic and Pseudomorphic Reactions

Mathias I. Mørch, Jack Thomas-Hunt, Amalie P. Laursen, Jesper Simonsen, Jens Plum Frandsen, Harikrishnan Vijayan, Mogens Christensen*

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review


The topotactical transformation of goethite to hexaferrite was investigated using 2D synchrotron powder diffraction. The relation between structure, size, and texture in the synthesis was investigated using combined quantitative texture analysis and Rietveld refinements. Based on the refinements, the topotaxial relation from the precursor (goethite) through the intermediate (hematite) and to the product (hexaferrite) could be understood. In all three cases, the orientation of texture and smallest crystallite dimension is along the closest packed oxygen lattice, the c-axis. In the intermediary step where goethite is converted to hematite, a pseudomorphic transition is observed where particle shape is maintained along the a- and b-axis. Furthermore, the structural relation from the intermediate to the product was demonstrated to aid the understanding of the final step in the topotactical transition. Based on this study, we conclude that synthesis can be designed to promote texture in materials beyond magnets by appropriate choice and understanding of precursor structure and morphology.

Original languageEnglish
JournalChemistry of Materials
Pages (from-to)1919-1927
Number of pages9
Publication statusPublished - 27 Feb 2024


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