Observation of lanthanum- and rare-earth-site ordering in T*-phase La2-x-yRxSryCuO4 (R=Sm, Eu, Gd, Tb).
Observation of lanthanum- and rare-earth-site ordering in T*-phase La2-x-yRxSryCuO4 (R=Sm, Eu, Gd, Tb).
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观察 T* 相 La2-x-yRxSryCuO4 (R=Sm、Eu、Gd、Tb) 中的镧和稀土位点排序。
DOI：
10.1103/physrevb.42.4808
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Rupp
中科院分区：
文献类型：
--
作者：
Tan;Budnick;Chen;Brewe;Cheong;Cooper;Rupp
在{ital T}{sup *}相La{下标2{负}{ital x}{负}{ital y}R{ital x}}Sr{下标{ital y}}CuO{下标4}结构中存在两个不相等的镧和（或）稀土（{ital R}）位。一个位点{ital M}与{ital T}结构（K{sub 2}NiF{sub 4}型）局部相似，另一个位点（{ital M}{prime}）与{ital T}{prime}结构（Nd{sub 2}CuO{sub 4}型）局部相似。通过对{ital T}-、{ital T}{prime}-和{ital T}{sup *}相材料中La和稀土元素的x射线吸收近边结构和扩展精细结构的研究，我们明确地发现，在{ital T}{sup *}相La{sub 0.9}{ital R}{sub 0.9}Sr{sub 0.2}CuO{sub 4} （{ital R}是Sm、Eu、Gd或Tb中的一种）中，La和{ital R}离子以有序的方式进入两个不相等的位置。La和稀土离子分别优先占据{ital M}和{ital M}{素数}位。
There are two inequivalent lanthanum and/or rare-earth ({ital R}) sites in the {ital T}{sup *}-phase La{sub 2{minus}{ital x}{minus}{ital y}R{ital x}}Sr{sub {ital y}}CuO{sub 4} structure. One site {ital M} is locally similar to that in the {ital T} structure (K{sub 2}NiF{sub 4}-type) and the other site ({ital M}{prime}) is locally similar to that in the {ital T}{prime} structure (Nd{sub 2}CuO{sub 4}-type). By studying the x-ray-absorption near-edge structure and extended fine structure of both La and rare-earth elements in {ital T}-, {ital T}{prime}-, and {ital T}{sup *}-phase materials, we find unambiguously that the La and {ital R} ions enter the two inequivalent sites in an ordered way in the {ital T}{sup *}-phase La{sub 0.9}{ital R}{sub 0.9}Sr{sub 0.2}CuO{sub 4} ({ital R} is one of Sm, Eu, Gd, or Tb). The La and the rare-earth ions preferentially occupy the {ital M} and {ital M}{prime} sites, respectively.