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; A Singh; Z-Y Li; J-S Zhou; H-T Jeng; G Y Guo; Je-Geun Park; L H Tjeng; C T Chen; D J Huang

doi:10.1038/ncomms15929

Jahn-Teller distortion driven magnetic polarons in magnetite

Nat Commun. 2017 Jun 29:8:15929. doi: 10.1038/ncomms15929.

Authors

H Y Huang^{1

2}, Z Y Chen³, R-P Wang⁴, F M F de Groot⁴, W B Wu¹, J Okamoto¹, A Chainani¹, A Singh¹, Z-Y Li⁵, J-S Zhou⁵, H-T Jeng³, G Y Guo^{6

7}, Je-Geun Park^{8

9}, L H Tjeng¹⁰, C T Chen¹, D J Huang^{1

3}

Affiliations

¹ National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.
² Program of Science and Technology of Synchrotron Light Source, National Tsing Hua University, Hsinchu 30013, Taiwan.
³ Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan.
⁴ Inorganic Chemistry and Catalysis, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands.
⁵ Department of Mechanical Engineering, Texas Material Institute, University of Texas at Austin, Austin, Texas 78712, USA.
⁶ Department of Physics, National Taiwan University, Taipei 10617, Taiwan.
⁷ Division of Physics, National Center for Theoretical Sciences, Hsinchu 30013, Taiwan.
⁸ Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea.
⁹ Center for Correlated Electron Systems, Institute for Basic Science, Seoul 08826, Korea.
¹⁰ Max Planck Institute for Chemical Physics of Solids, Nöthnitzerstr. 40, 01187 Dresden, Germany.

Abstract

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 Fe²⁺ and Fe³⁺ states. Comparison of the experimental 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 are best explained as magnetic polarons.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.