The first known magnetic mineral, magnetite (Fe3O4), has unusual properties which have fascinated mankind for centuries; it undergoes the Verwey transition at TV∼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 Fe2+ and Fe3+ states. Comparison of the RIXS results with crystal-field multiplet calculations shows that the spin-orbital dd excitons of the Fe2+ sites arise from a tetragonal Jahn-Teller active polaronic distortion of the Fe2+O6 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.
@article{arxiv.1512.07957,
title = {Jahn-Teller distortion driven magnetic polarons in magnetite},
author = {H. Y. Huang and Z. Y. Chen and R. -P. Wang and F. M. F. de Groot and W. B. Wu and J. Okamoto and A. Chainani and J. -S. Zhou and H. -T. Jeng and G. Y. Guo and Je-Geun Park and L. H. Tjeng and C. T. Chen and D. J. Huang},
journal= {arXiv preprint arXiv:1512.07957},
year = {2017}
}