Control of the third dimension in copper-based square-lattice antiferromagnets
Control of the third dimension in copper-based square-lattice antiferromagnets
复制标题
DOI：
10.1103/physrevb.93.094430
复制
发表时间：
2016-03-25
影响因子：
3.7
通讯作者：
Manson, Jamie L.
中科院分区：
文献类型：
--
作者：
Goddard, Paul A.;Singleton, John;Manson, Jamie L.
采用混合配体合成方法，合成了一类准二维反铁磁体，即[Cu（HF_2）（pyz）（2）] ClO_4 [pyz =吡嗪]，[CuL_2（pyz）（2）]（ClO_4）（2）[L = pyO =吡啶-N-氧化物和4-phpy-O = 4-苯基吡啶-N-氧化物.这些材料被证明具有等效的二维[Cu（pyz）（2）]（2+）近正方形层，但表现出层间距从6.5713到16.777埃不等，如轴向配体所示。我们通过X射线衍射、电子自旋共振、脉冲磁场和准静态磁场以及μ子自旋旋转等方法研究了该系列化合物的结构和磁性，并将其与典型的二维磁性聚合物Cu（pyz）（2）（ClO 4）（2）进行了比较。我们发现，在实验误差的范围内，在我们的材料家族中的二维，层内交换耦合在很大程度上不受轴向配体取代的影响，而所观察到的磁有序温度（1.91 K的材料与HF 2轴向配体，1.70 K的pyO和1.63 K的4-phpy-O）随着层分离的增加而缓慢下降。尽管该家族和Cu（pyz）（2）（ClO 4）（2）具有共同的结构基序，但后者具有显着更强的二维交换相互作用，因此具有更高的有序温度。我们讨论了这些结果，以及可能驱动这些材料中的长程有序的机制，在偏离理想的S = 1/2二维正方晶格海森堡反铁磁体。特别是，我们发现，自旋交换各向异性的层内相互作用和层间耦合（交换，偶极，或两者）需要考虑所观察到的有序温度，层内各向异性变得更加重要，因为层被拉得更远。
Using a mixed-ligand synthetic scheme, we create a family of quasi-two-dimensional antiferromagnets, namely, [Cu(HF2)(pyz)(2)]ClO4 [pyz = pyrazine], [CuL2(pyz)(2)](ClO4)(2) [L = pyO = pyridine-N-oxide and 4-phpy-O = 4-phenylpyridine-N-oxide. These materials are shown to possess equivalent two-dimensional [Cu(pyz)(2)](2+) nearly square layers, but exhibit interlayer spacings that vary from 6.5713 to 16.777 angstrom, as dictated by the axial ligands. We present the structural and magnetic properties of this family as determined via x-ray diffraction, electron-spin resonance, pulsed-and quasistatic-field magnetometry and muon-spin rotation, and compare them to those of the prototypical two-dimensional magnetic polymer Cu(pyz)(2)(ClO4)(2). We find that, within the limits of the experimental error, the two-dimensional, intralayer exchange coupling in our family of materials remains largely unaffected by the axial ligand substitution, while the observed magnetic ordering temperature (1.91 K for the material with the HF2 axial ligand, 1.70 K for the pyO and 1.63 K for the 4-phpy-O) decreases slowly with increasing layer separation. Despite the structural motifs common to this family and Cu(pyz)(2)(ClO4)(2), the latter has significantly stronger two-dimensional exchange interactions and hence a higher ordering temperature. We discuss these results, as well as the mechanisms that might drive the long-range order in these materials, in terms of departures from the ideal S = 1/2 two-dimensional square-lattice Heisenberg antiferromagnet. In particular, we find that both spin-exchange anisotropy in the intralayer interaction and interlayer couplings (exchange, dipolar, or both) are needed to account for the observed ordering temperatures, with the intralayer anisotropy becoming more important as the layers are pulled further apart.