Department of Chemistry, McMaster University, Hamilton, L8S 4M1, Canada.
J Phys Condens Matter. 2011 Apr 27;23(16):164213. doi: 10.1088/0953-8984/23/16/164213. Epub 2011 Apr 6.
The geometrically frustrated, B-site ordered, S = 1/2, double perovskites Sr(2)CaReO(6) and Sr(2)MgReO(6), which show spin frozen magnetic ground states, have been investigated using neutron powder diffraction (ND) and neutron pair distribution function (NPDF) analysis in a search for evidence for atomic positional disorder. For both materials, data were taken above and below the spin freezing temperatures of ∼ 14 K and ∼ 45 K for the CaRe and MgRe phases, respectively. In both cases the fully B-site ordered model was in excellent agreement with the data, both ND and NPDF, at all temperatures studied. Thus, the structure of these materials, from the average and the local perspectives, is very well described by the fully B-site ordered model, which raises questions concerning the origin of the spin glass ground state. These results are compared with those for the spin glass pyrochlore Y(2)Mo(2)O(7) and other B-site ordered double perovskites.
具有几何阻挫、B 位有序、S = 1/2 的双钙钛矿 Sr(2)CaReO(6) 和 Sr(2)MgReO(6) 表现出自旋冻结的磁基态，我们使用中子粉末衍射 (ND) 和中子配对分布函数 (NPDF) 分析对其进行了研究，以寻找原子位置无序的证据。对于这两种材料，数据是在 CaRe 和 MgRe 相的自旋冻结温度约为 14 K 和 45 K 以上和以下的温度下采集的。在所有研究的温度下，完全 B 位有序模型都与 ND 和 NPDF 数据非常吻合。因此，从平均和局部的角度来看，这些材料的结构都可以用完全 B 位有序模型很好地描述，这就引发了对自旋玻璃基态起源的疑问。这些结果与自旋玻璃烧绿石 Y(2)Mo(2)O(7) 和其他 B 位有序双钙钛矿的结果进行了比较。
