Real-space imaging of the Verwey transition at the (100) surface of magnetite

J. de la Figuera, Z. Novotny, M. Setvin, T. Liu, Z. Mao, G. Chen, A. T. N'Diaye, M. Schmid, U. Diebold, A. K. Schmid, G. S. Parkinson

1 Instituto de Química-Física "Rocasolano", CSIC, Madrid 28006, Spain
2 Institut für Angewandte Physik, Technische Universität Wien, 1040 Wien, Austria
3 Tulane University, New Orleans, Louisiana 70118, U.S.A.
4 Lawrence Berkeley National Laboratory, Berkeley, California 94720, U.S.A.

Phys. Rev. B 88 (2013) 161410(R)

Effects of the Verwey transition on the (100) surface of magnetite were studied using scanning tunelling microscopy and spin polarized low-energy electron microsccopy. On cooling through the transition temperature TV, the initially flat surface undergoes a roof-like distortion with a periodicity of ~ 0.5 µm due to ferroelastic twinning within monoclinic domains of the low-temperature monoclinic structure. The monoclinic c axis orients in the surface plane, along the [001]c directions. At the atomic scale, the charge-ordered (√2 × √2)R45° reconstruction of the (100) surface is unperturbed by the bulk transition, and is continuous over the twin boundaries. Time resolved low-energy electron microscopy movies reveal the structural transition to be first-order at the surface, indicating that the bulk transition is not an extension of the Verwey-like (√2 × √2)R45° reconstruction. Although conceptually similar, the charge-ordered phases of the (100) surface and sub-TV bulk of magnetite are unrelated phenomena.

Corresponding author: Juan de la Figuera. Reprints also available from Michael Schmid (schmid< encoded email address >).

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