Jahn-Teller Distortion Driven Magnetic Polarons in Magnetite
Hsiao-Yu Huang1*, Zhi-Yin Chen2, Ru-Pan Wang3, F. M. F. de Groot3, Wen-Bin Wu1, Jun Okamoto1, Ashish Chainani1, Jianshi Zhou4, Horng-Tay Jeng2, Guang-Yu Guo5,6, Je-Geun Park7,8, Liu Hao Tjeng9, Chien-Te Chen1, Di-Jing Huang1,2
1National Synchrotron Radiation Research Center, Hsinchu, Taiwan
2Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
3Department of Inorganic Chemistry and Catalysis, Utrecht University, Utrecht, Netherlands
4Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas, USA
5Department of Physics, National Taiwan Universit, Taipei, Taiwan
6Physics Division, National Center for Theoretical Sciences, Hsinchu, Taiwan
7Department of Physics and Astronomy, Seoul National University, Seoul, Korea
8Center for Correlated Electron Systems, Institute for Basic Science, Seoul, Korea
9Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
* presenting author:Hsiao-Yu Huang, email:physh.physics@gmail.com
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.

Keywords: Resonant inelastic X-ray scattering