Journal Article

Jahn-Teller distortion driven magnetic polarons in magnetite

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

2017

Overview

The first known magnetic mineral, magnetite, has unusual properties, which have fascinated mankind for centuries; it undergoes the Verwey transition around 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 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 experimental 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 are best explained as magnetic polarons. The Verwey transition of magnetite is complex due to the coexistence of strong correlations and electron-phonon coupling. Here, the authors use resonant inelastic X-ray scattering to show evidence for magnetic polarons in magnetite and provide insight into the nature of the transition.

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Nature Portfolio
• Subject: 639/766/119/995 / Distortion / Electrical conductivity / Electrical resistivity / Energy / Excitons / Humanities and Social Sciences / Inelastic scattering / Iron / Magnetic properties / Magnetite / multidisciplinary / Physics / Polarons / Science / Science (multidisciplinary) / Symmetry / Temperature effects / X-ray scattering / X-rays