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arXiv · 1512.07957

Jahn-Teller distortion driven magnetic polarons in magnetite

H. Y. Huang·Z. Y. Chen·R. -P. Wang·F. M. F. de Groot·W. B. Wu·J. Okamoto·A. Chainani·J. -S. Zhou·H. -T. Jeng·G. Y. Guo·Je-Geun Park·L. H. Tjeng·C. T. Chen·D. J. Huang
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Abstract

The first known magnetic mineral, magnetite (Fe$_3$O$_4$), has unusual properties which have fascinated mankind for centuries; it undergoes the Verwey transition at $T_{\rm V}$ $\sim$120 K with an abrupt change in structure and electrical conductivity. The mechanism of the Verwey transition however remains contentious. Here we use resonant inelastic X-ray scattering (RIXS) over a wide temperature range across the Verwey transition to identify and separate out the magnetic excitations derived from nominal Fe$^{2+}$ and Fe$^{3+}$ states. Comparison of the RIXS results with crystal-field multiplet calculations shows that the spin-orbital $dd$ excitons of the Fe$^{2+}$ sites arise from a tetragonal Jahn-Teller active polaronic distortion of the Fe$^{2+}$O$_6$ octahedra. These low-energy excitations, which get weakened for temperatures above 350 K but persist at least up to 550 K, are distinct from optical excitations and best explained as magnetic polarons.

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H. Y. Huang, Z. Y. Chen, R. -P. Wang, F. M. F. de Groot, W. B. Wu, J. Okamoto, A. Chainani, J. -S. Zhou, H. -T. Jeng, G. Y. Guo, Je-Geun Park, L. H. Tjeng, C. T. Chen, D. J. Huang. 2016-08-13. Jahn-Teller distortion driven magnetic polarons in magnetite. https://doi.org/10.1038/ncomms15929

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