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Synthesis, crystal structure and magnetic properties of an Os-containing pillared perovskite La5OS3MnO16

机译:含Os的柱状钙钛矿La5OS3MnO16的合成,晶体结构和磁性

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A new Os-containing, pillared perovskite, La5Os3MnO16, has been synthesized by solid state reaction in sealed quartz tubes. This extends the crystal chemistry of these materials which had been known only for Mo and Re, previously. The crystal structure has been characterized by X-ray and neutron powder diffraction and is described in space group C-I with parameters a = 7.9648(9) Angstrom; b = 8.062(1) Angstrom; c = 10.156(2) Angstrom, alpha = 90.25(1)degrees, beta = 95.5(1)degrees; gamma = 89.95(2)degrees, for La5Os3MnO16. The compound is isostructural with the corresponding La5Re3MnO16 phase. A very short Os-Os distance of 2.50(1) Angstrom was found in the dimeric pillaring unit, Os2O10, suggestive of a triple bond as demanded by electron counting. Nearly spin only values for the effective moment for Os5+ (S = 3/2) and Mn2+ (S = 5/2) were derived from magnetic susceptibility data. Evidence for magnetic transitions was seen near similar to180 and 80 K. Neutron diffraction data indicate that T-c is 170(5) K. The magnetic structure of La5Os3MnO16 at 7 K was solved revealing that Os5+ and Mn2+ form ferrimagnetically coupled layers with antiferromagnetic interlayer ordering. The ordered moments are 4.2(4) mu(B) for Mn2+ and 1.5(4) mu(B) for Os5+, which are reduced from the respective spin only values of 5.0 and 3.0 mu(B). The observation of net ferrimagnetic (antiparallel) intraplanar coupling between Os5+ (t(2)(g3)) and Mn2+ (t(2g)(3)e(g)(2)) is interesting as it appears to contradict the Goodenough-Kanamori rules for 180degrees superexchange. (C) 2004 Elsevier Inc. All rights reserved.
机译:在密封石英管中通过固相反应合成了一种新型的含Os的柱状钙钛矿La5Os3MnO16。这扩展了以前仅对于Mo和Re已知的这些材料的晶体化学。晶体结构已通过X射线和中子粉末衍射表征,并描述在空间群C-1中,参数a = 7.9648(9)埃; b = 8.062(1)埃; c = 10.156(2)埃,alpha = 90.25(1)度,beta = 95.5(1)度;对于La5Os3MnO16,γ= 89.95(2)度。该化合物与相应的La5Re3MnO16相同构。在二聚体支柱单元Os2O10中发现了非常短的Os-Os距离,为2.50(1)埃,暗示了电子计数所需的三键。从磁化率数据中得出,Os5 +(S = 3/2)和Mn2 +(S = 5/2)的有效力矩几乎只有自旋值。可以看到接近180和80 K的磁跃迁证据。中子衍射数据表明T-c为170(5)K.La5Os3MnO16在7 K时的磁性结构得到解析,揭示Os5 +和Mn2 +形成具有反铁磁层间顺序的铁磁耦合层。 Mn2 +的有序矩为4.2(4)mu(B),Os5 +的有序矩为1.5(4)mu(B),它们分别从5.0和3.0 mu(B)的自旋值减小。 Os5 +(t(2)(g3))和Mn2 +(t(2g)(3)e(g)(2))之间的纯亚铁磁(反平行)平面内耦合的观察很有趣,因为它似乎与Goodenough-Kanamori矛盾180度超级交换规则。 (C)2004 Elsevier Inc.保留所有权利。

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