Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, Departamento de Física de Materia Condensada, Pedro Cerbuna 12, 50009 Zaragoza, Spain.
J Synchrotron Radiat. 2012 Mar;19(Pt 2):159-73. doi: 10.1107/S0909049512001367. Epub 2012 Feb 2.
The pattern of charge modulations and local anisotropies below the Verwey transition has been determined and quantified in high-quality Fe(3)O(4) single crystals and thin films grown on MgO by using resonant X-ray scattering at the Fe K-edge. The energy, polarization and azimuthal angle dependencies of an extensive set of reflections with potential sensitivity to charge or local anisotropy orderings have been analyzed to explore their origins. A charge disproportion on octahedral B sites of 0.20 ± 0.05 e(-) with [0 0 1] and [1 1 0] cubic periodicities has been confirmed, while no significant charge disproportion has been obtained with [0 0 1/2] cubic periodicity. Additional charge modulations in the monoclinic a-b plane are also present. In addition, the occurrence of new forbidden (1, 1, 0) and (0, 0, 2n + 1/2) cubic reflections that arise from the anisotropy of the local structure around different tetrahedral and octahedral Fe atoms is shown. This complex pattern of weak charge modulations and local anisotropies is fully compatible with the low-temperature crystal structure refined in the non-polar C2/c space group and disproves any bimodal charge disproportion of the octahedral Fe atoms.
在使用 Fe K 边缘共振 X 射线散射技术对在 MgO 上生长的高质量 Fe(3)O(4) 单晶和薄膜进行研究后，确定并量化了低于 Verwey 转变的电荷调制和局部各向异性模式。分析了一组具有潜在电荷或局部各向异性有序敏感性的广泛反射的能量、极化和方位角依赖性，以探索其起源。证实了八面体 B 位上的电荷离域为 0.20 ± 0.05 e(-)，具有[0 0 1]和[1 1 0]立方周期性，而[0 0 1/2]立方周期性则没有明显的电荷离域。此外，在单斜 a-b 平面中还存在额外的电荷调制。此外，还显示了由于四面体和八面体 Fe 原子周围局部结构各向异性而产生的新的禁带（1,1,0）和（0,0,2n+1/2）立方反射的出现。这种微弱的电荷调制和局部各向异性的复杂模式与非极性 C2/c 空间群中低温晶体结构的精修完全一致，并否定了八面体 Fe 原子的任何双峰电荷离域。
