Lawrence Gaynor B, Wildman Eve J, Stenning Gavin B G, Ritter Clemens, Fauth Francois, Mclaughlin Abbie C
The Chemistry Department, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, Scotland.
Institut Laue-Langevin, 71 Avenue des Martyrs, 38000 Grenoble, France.
Inorg Chem. 2020 Jun 1;59(11):7553-7560. doi: 10.1021/acs.inorgchem.0c00447. Epub 2020 May 20.
Several different mechanisms of magnetoresistance (MR) have been observed in 1111 LnMnAsOF oxypnictides (Ln = lanthanide) as a result of magnetic coupling between the Mn and Ln. Such phases also exhibit interesting magnetic phase transitions upon cooling. SrMnCrAsO has been synthesized to investigate if it is possible to observe MR and/or magnetic phase transitions as a result of magnetic coupling between the Mn and Cr. SrMnCrAsO crystallizes in the tetragonal space group 4/ containing alternating MO and M'As layers, and neutron diffraction results demonstrate that the actual stoichiometry is SrMnCrAsO. Cation order is present between Mn and Cr, with Cr predominantly occupying the square planar MO site. Below 410 K, the magnetic moments of the Mn/Cr ions in the M'As sublattice exhibit G-type antiferromagnetic order. The Mn/Cr moments within the MO layer order below 167 K with a KNiF-type antiferromagnetic structure that simultaneously induces a spin flip of the magnetic moments in the M'As layers from a G-type to a C-type antiferromagnetic arrangement. The results demonstrate that the superexchange interactions are finely balanced in SrMnCrAsO. SrMnCrAsO is semiconducting, and there is no evidence of MR.
由于Mn和Ln之间的磁耦合，在1111型LnMnAsOF氧族氮化物（Ln = 镧系元素）中观察到了几种不同的磁电阻（MR）机制。这类相在冷却时也表现出有趣的磁相变。已合成SrMnCrAsO以研究是否有可能观察到由于Mn和Cr之间的磁耦合而产生的MR和/或磁相变。SrMnCrAsO结晶于四方空间群4/，包含交替的MO和M'As层，中子衍射结果表明实际化学计量比为SrMnCrAsO。Mn和Cr之间存在阳离子有序，Cr主要占据平面正方形MO位点。在410 K以下，M'As亚晶格中Mn/Cr离子的磁矩呈现G型反铁磁有序。MO层内的Mn/Cr磁矩在167 K以下有序排列，具有KNiF型反铁磁结构，同时导致M'As层中磁矩的自旋翻转，从G型反铁磁排列转变为C型反铁磁排列。结果表明，SrMnCrAsO中的超交换相互作用得到了精细平衡。SrMnCrAsO是半导体，没有MR的证据。
