Jahn-Teller distortion driven magnetic polarons in magnetite.
Jahn-Teller distortion driven magnetic polarons in magnetite.
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DOI：
10.1038/ncomms15929
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发表时间：
2017-06-29
影响因子：
16.6
通讯作者：
Huang DJ
中科院分区：
文献类型：
--
作者：
Huang HY;Chen ZY;Wang RP;de Groot FMF;Wu WB;Okamoto J;Chainani A;Singh A;Li ZY;Zhou JS;Jeng HT;Guo GY;Park JG;Tjeng LH;Chen CT;Huang DJ
第一种已知的磁性矿物磁铁矿具有不寻常的特性，几个世纪以来一直让人类着迷。它在 120 K 左右经历 Verwey 转变，结构和电导率发生突变。然而，韦尔威过渡的机制仍然存在争议。在这里，我们使用跨越 Verwey 转变的宽温度范围内的共振非弹性 X 射线散射来识别和分离出源自标称 Fe2+ 和 Fe3+ 态的磁激发。实验结果与晶体场多重态计算的比较表明，Fe2+ 位点的自旋轨道 dd 激子源自 Fe2+O6 八面体的四方 Jahn-Teller 活性极化畸变。这些低能激发在温度高于 350°K 时会减弱，但至少持续到 550°K，与光激发不同，最好将其解释为磁极化子。由于强相关性和电子声子耦合的共存，磁铁矿的Verwey转变非常复杂。在这里，作者利用共振非弹性 X 射线散射来显示磁铁矿中磁极化子的证据，并深入了解转变的本质。
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. 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.