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arXiv · 2609.02368

Magneto-Structural Coupling Enables Cryogenic Cation Redistribution in a Spinel Oxide

Yifeng Han·Yixing Zhao·Yunbo Ou·Feiran Shen·Lunhua He·Ligang Xu·Mingxue Tang·Jared Matteucci·Zexiao Zhang·Xiaoli Ma·Xiaohui Yu·Zheng Deng·Man-Rong Li·Alexandra Navrotsky
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Abstract

Ionic transport in oxides is generally frozen at cryogenic temperatures, where thermal energy lies far below typical cation-migration barriers. Neutron powder diffraction reveals progressive Fe/Mg redistribution between tetrahedral (A) and octahedral (B) sites in the spinel Mg0.5Fe0.5TiFeO4 upon cooling from 200 K to 5 K. A-site Fe occupancy increases toward near completion at 5 K within Rietveld resolution, while Ti remains on the B site. This exchange coincides with complex magnetic correlations rather than a classical thermally activated window. Low-temperature magnetostrictive volume changes indicate strong spin-lattice coupling, but do not identify magnetostriction as the sole thermodynamic driver. Room-temperature high-pressure X-ray diffraction produces the opposite occupancy trend, showing that volume contraction alone cannot explain the cryogenic site exchange. These results point to magneto-structural free-energy minimization as a plausible mechanism for unlocking cryogenic cation mobility in a correlated spinel oxide.

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Yifeng Han, Yixing Zhao, Yunbo Ou, Feiran Shen, Lunhua He, Ligang Xu, Mingxue Tang, Jared Matteucci, Zexiao Zhang, Xiaoli Ma, Xiaohui Yu, Zheng Deng, Man-Rong Li, Alexandra Navrotsky. 2026-09-02. Magneto-Structural Coupling Enables Cryogenic Cation Redistribution in a Spinel Oxide. https://arxiv.org/abs/2609.02368

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