Charge ordered structure of magnetite Fe 3 O 4 below the Verwey transition
Charge ordered structure of magnetite Fe 3 O 4 below the Verwey transition
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DOI：
10.1103/physrevb.66.214422
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发表时间：
2002-12
影响因子：
3.7
通讯作者：
Jon P. Wright;J. Attfield;P. Radaelli
中科院分区：
文献类型：
--
作者：
Jon P. Wright;J. Attfield;P. Radaelli
利用高分辨率中子和同步加速器x射线粉末衍射数据，对Verwey跃迁下高化学计量磁铁矿（fe3o4）的晶体结构进行了细化。该模型具有单斜P2/c对称单元，原子位置具有正交Pmca伪对称约束，包含4个独立的八面体B位铁原子。扩展和收缩的bo6八面体的存在，以及不同B位电荷之间不相等的库仑斥力引起的B-B距离的分布，证明了电荷的有序性。B-B距离与二聚体的形成不一致。B- o和B-B相互作用之间的竞争导致两个B位阳离子的极性位移。电荷排序具有主要的密度调制[001]，这减轻了电子态密度的嵌套不稳定性，但也发生了第二次[00]相位调制。Verwey跃迁的单斜畸变与轨道简并fe2 +局域化驱动的宏观菱形磁致伸缩相一致，与具有正交晶格对称的微观电荷有序畸变相一致。
The crystal structure of highly stoichiometric magnetite (Fe 3 O 4 ) below the Verwey transition has been refined from high-resolution neutron and synchrotron x-ray powder-diffraction data. The refined model has a monoclinic P2/c symmetry cell with orthorhombic Pmca pseudosymmetry constraints on the atomic positions, and contains four independent octahedral B site iron atoms. Charge ordering is evidenced by the presence of expanded and contracted BO 6 octahedra, and by the distribution of B-B distances resulting from unequal Coulombic repulsions between the different B site charges. The B-B distances are inconsistent with dimer formation. Competition between the B-O and B-B interactions results in polar displacements of two of the B site cations. The charge ordering has a predominant [001] density modulation, which relieves a nesting instability in the electronic density of states, but a second [00] phase modulation also occurs. The monoclinic distortion at the Verwey transition is consistent with a macroscopic rhombohedral magnetostriction, driven by the localization of orbitally degenerate Fe 2 + , coincident with the microscopic charge ordering distortions that have an orthorhombic lattice symmetry.