The magnetic structures of the mixed layer pnictide oxide compounds Sr(2)Mn(3)Pn(2)O(2) (Pn=As, Sb)
The magnetic structures of the mixed layer pnictide oxide compounds Sr(2)Mn(3)Pn(2)O(2) (Pn=As, Sb)
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DOI：
10.1016/0925-8388(95)02066-7
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发表时间：
1996-04-15
影响因子：
6.2
通讯作者：
Kauzlarich, SM
中科院分区：
文献类型：
--
作者：
Brock, SL;Raju, NP;Kauzlarich, SM
本文报道了Sr（2）Mn（3）Pn（2）O（2）（Pn = As，Sb）的中子粉末衍射结果，并测定了其磁结构。其化学结构可以描述为BaAl 4型Mn（2）Pn（2）（2-）层与MnO 22-层的1：1共生，所述MnO 22-层与铜酸盐超导体中发现的CuO 2平面同构。Sr 2+阳离子将两层分开。存在两个独立的磁性亚晶格Mn（1）和Mn（2），分别与MnO_（22-）和Mn（2）Pn（2）（2-）层有关。两个亚晶格都具有四重对称性，Mn（2）是原始的，Mn（1）是中心的。每个子晶格内的层间距为约10埃，子晶格之间的层间距为约5埃。由于Mn（1）亚晶格的中心化，最近的MnO 22-层之间的相互作用抵消，Mn（1）和Mn（2）亚晶格之间的相互作用也是如此。Mn（2）亚晶格在340 K（As）和300 K（Sb）左右的相对高温下有序，具有G（z）型结构，k =（000），在4 K时饱和磁矩为3.4 μ（B）.在低温下，出现了新的磁源反射，这可以归因于Mn（1）亚晶格，但每个化合物的细节是不同的。Sr 2 Mn 3 Sb 2 O 2的Mn（1）磁矩低于65 K，k =（1/21/20）沿着（100），即垂直于Mn（2）自旋，具有明显更大的4.2 μ（B）磁矩。在Sr_2Mn_3As_2O_2中，人们看到在75 K以下的弱得多的反射，其中最突出的是仅显示二维相关性的沃伦线形特征。因此，在Sr_2Mn_3As_2O_2中，Mn（1）亚晶格在4K以下的长程意义上可能不有序。这些锰pnictide氧化物的各个亚晶格的性质进行了比较与类似的磁性亚晶格的其他化合物。
Neutron powder diffraction results are reported for the compounds Sr(2)Mn(3)Pn(2)O(2) (Pn = As, Sb), and the magnetic structures are determined. The chemical structure can be described as a 1:1 intergrowth of Mn(2)Pn(2)(2-) layers of the BaAl4 type with MnO22- layers isostructural with the CuO2 planes found in cuprate superconductors. The Sr2+ cations separate the two layers. Two independent magnetic sublattices exist, Mn(1) and Mn(2), associated with the MnO22- and Mn(2)Pn(2)(2-) layers respectively. Both sublattices have tetragonal symmetry, Mn(2) being primitive and Mn(1) being centered. The interlayer spacing within each sublattice is about 10 Angstrom and between the sublattices it is about 5 Angstrom. Owing to the centering of the Mn(1) sublattice, interactions between the nearest MnO22- layers cancel, as do interactions between the Mn(1) and Mn(2) sublattices. The Mn(2) sublattice is found to order at the relatively high temperatures of about 340 K (As) and 300 K (Sb) in a type G(z) structure, k = (000) with a saturation moment of 3.4 mu(B) at 4 K. At low temperatures new reflections of magnetic origin appear which can be assigned to the Mn(1) sublattice, but the details are different for each compound. The Mn(1) moments for Sr2Mn3Sb2O2 order below 65 K with k = (1/21/20) along (100), i.e. normal to the Mn(2) spins, with a significantly larger moment of 4.2 mu(B). In Sr2Mn3As2O2 one sees much weaker reflections below 75 K, the most prominent of which shows a Warren line shape characteristic of two-dimensional correlations only. Thus it appears that the Mn(1) sublattice may not order in the long range sense down to 4K in Sr2Mn3As2O2. The properties of the individual sublattices of these manganese pnictide oxides are compared with similar magnetic sublattices of other compounds.