Crystal structures of spin-Jahn–Teller-ordered MgCr2O4 and ZnCr2O4
Crystal structures of spin-Jahn–Teller-ordered MgCr2O4 and ZnCr2O4
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DOI：
10.1088/0953-8984/25/32/326001
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发表时间：
2013-02
期刊：
影响因子：
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通讯作者：
M. Kemei;Phillip T. Barton;S. Moffitt;M. Gaultois;Joshua A. Kurzman;R. Seshadri;M. Suchomel;Young-Il Kim
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文献类型：
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作者：
M. Kemei;Phillip T. Barton;S. Moffitt;M. Gaultois;Joshua A. Kurzman;R. Seshadri;M. Suchomel;Young-Il Kim
磁性氧化尖晶石MgCr2O4和ZnCr2O4的磁性有序结构变化有助于减轻几何挫折。高分辨率同步加速器x射线散射分析表明，低温结构可以用四边形I41/amd和正交Fddd对称的两相模型很好地描述。在这些低温条件下，焦绿盐晶格的Cr4四面体发生畸变，其中Fddd相的畸变比I41/amd相更大。自旋- jhn - teller畸变比NiCr2O4和CuCr2O4等一阶jhn - teller尖晶石的畸变大约小一个数量级。与NiCr2O4和CuCr2O4类似，我们进一步提出，磁有序的精确性质本身可以为结构变化提供第二种驱动力。
Magnetic ordering in the geometrically frustrated magnetic oxide spinels MgCr2O4 and ZnCr2O4 is accompanied by a structural change that helps to relieve the frustration. Analysis of high-resolution synchrotron x-ray scattering reveals that the low-temperature structures are well described by a two-phase model of tetragonal I41/amd and orthorhombic Fddd symmetries. The Cr4 tetrahedra of the pyrochlore lattice are distorted at these low-temperatures, with the Fddd phase displaying larger distortions than the I41/amd phase. The spin-Jahn–Teller distortion is approximately one order of magnitude smaller than is observed in first-order Jahn–Teller spinels such as NiCr2O4 and CuCr2O4. In analogy with NiCr2O4 and CuCr2O4, we further suggest that the precise nature of magnetic ordering can itself provide a second driving force for structural change.