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Structure change across the Morin transition temperature of single crystal α-Fe<sub>2</sub>O<sub>3</sub>

ORAL

Abstract

Alpha-ferric oxide (α-Fe2O3) has been the subject of extensive studies aiming to determine the relationship between spontaneous magnetic moments and structure. Below its Néel temperature TN = 948 K, the iron magnetic moments are antiferromagnetically ordered, previous studies by neutron diffraction across the Morin temperature (TM=263 K) have found the Fe moments lie in the rhombohedral (111) plane above the TM and form the canted spin structure that gives rise to weak ferromagnetism (FM), upon cooling through TM, the easy axis of spins rotates to Hexagonal c axis and magnetization drops. The weak FM is believed to be caused by Dzyaloshinskii-Moriya interaction (DMI). However, S-state for Fe3+ makes the spin-orbit couple and therefore DMI negligible. Here, we synthesized high-quality single crystal α-Fe2O3 and used synchrotron X-Ray diffraction to explore likely subtle change of local structure, which might be driving force for the change of easy axis and spin canting across TM. We found the unit cell size and Fe-O bond length decreases upon cooling, the Fe-O octahedral become less distorted, the long axis of the octahedral shifted towards Hexagonal c axis.

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Presenters

  • Jiaming He

    University of Texas at Austin, Texas Materials Institute, University of Texas at Austin, Materials Science and Engineering Program, Mechanical Engineering, University of Texas at Austin

Authors

  • Jiaming He

    University of Texas at Austin, Texas Materials Institute, University of Texas at Austin, Materials Science and Engineering Program, Mechanical Engineering, University of Texas at Austin

  • Suyin Wang

    University of Chicago, NSF’s ChemMatCARS, The University of Chicago

  • Yu-sheng Chen

    University of Chicago, ChemMatCARS, University of Chicago, NSF’s ChemMatCARS, The University of Chicago

  • Jianshi Zhou

    University of Texas at Austin, Materials Science and Engineering Program, Department of Mechanical Engineering, University of Texas at Austin, University of Texas (Austin, USA), University of Texas, Texas Materials Institute, University of Texas at Austin, Materials Science and Engineering Program, Mechanical Engineering, University of Texas at Austin