Determining the anisotropy and exchange parameters of polycrystalline spin-1 magnets
Determining the anisotropy and exchange parameters of polycrystalline spin-1 magnets
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DOI：
10.1088/1367-2630/ab3dba
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发表时间：
2019-09-12
影响因子：
3.3
通讯作者：
Goddard, P. A.
中科院分区：
文献类型：
--
作者：
Blackmore, W. J. A.;Brambleby, J.;Goddard, P. A.
虽然低维S = 1反铁磁体仍然有很大的兴趣，但难以获得最新材料的高质量单晶阻碍了这一领域的实验研究。多晶样品更容易生产，但在从粉末数据中提取各向异性系统的磁性方面存在固有的问题。在讨论了各种测量技术的粉末平均的效果之后，我们提出了一种使用热力学测量来克服这个问题的方法。特别是，我们专注于是否有可能使用现成的实验室设备来测试多晶各向异性样品的磁性能。我们使用具有可忽略的交换相互作用的磁体[Ni（H2O）（2）（3，5-二甲基吡啶）（4）]（BF 4）（2）和Ni（H2O）（2）（乙酸酯）（2）（4-甲基吡啶）（2）以及反铁磁体[Ni（H2O）（2）（吡嗪）（2）]（BF 4）（2）来测试我们的方法的功效，并且表明我们能够在每种情况下提取各向异性参数。从热力学测量得到的结果进行检查对电子自旋共振和中子衍射。我们还提出了一个密度泛函方法，它结合了自旋轨道耦合来估计[Ni（H2O）（2）（吡嗪）（2）]（BF 4）（2）的各向异性的大小。
Although low-dimensional S = 1 antiferromagnets remain of great interest, difficulty in obtaining high-quality single crystals of the newest materials hinders experimental research in this area. Polycrystalline samples are more readily produced, but there are inherent problems in extracting the magnetic properties of anisotropic systems from powder data. Following a discussion of the effect of powder-averaging on various measurement techniques, we present a methodology to overcome this issue using thermodynamic measurements. In particular we focus on whether it is possible to characterise the magnetic properties of polycrystalline, anisotropic samples using readily available laboratory equipment. We test the efficacy of our method using the magnets [Ni(H2O)(2)(3,5-lutidine)(4)](BF4)(2) and Ni(H2O)(2) (acetate)(2)(4-picoline)(2), which have negligible exchange interactions, as well as the antiferromagnet [Ni(H2O)(2)(pyrazine)(2)](BF4)(2), and show that we are able to extract the anisotropy parameters in each case. The results obtained from the thermodynamic measurements are checked against electron-spin resonance and neutron diffraction. We also present a density functional method, which incorporates spin-orbit coupling to estimate the size of the anisotropy in [Ni(H2O)(2)(pyrazine)(2)](BF4)(2).