The crystal structures and magnetic properties of TiFeSi coexisting in hexagonal and orthorhombic symmetries
The crystal structures and magnetic properties of TiFeSi coexisting in hexagonal and orthorhombic symmetries
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DOI：
10.1016/j.jallcom.2021.158617
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发表时间：
2021-05
影响因子：
6.2
通讯作者：
M. Marshall;J. Sanford;W. Shelton;W. Xie
中科院分区：
文献类型：
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作者：
M. Marshall;J. Sanford;W. Shelton;W. Xie
具有空间群P213(S.G.P213)的手性FeSi型结构的相互缠绕的螺旋骨架启发了我们研究其他非中心对称化合物，特别是具有不同FeSi骨架的111型相。根据价电子数和空间群对各种含FeSi的111型相进行了总结。在这项工作中，我们主要研究了非中心对称的TiFeSi相。对六方相Fe2P型和已报道的正交相TiFeSi型(α-TiFeSi型)的晶体结构分析表明，两种结构之间存在着超晶格关系，这促使我们进行了六方相和正交相模型的总能量计算。在理论预测的基础上，提出了一种六方相(β-TiFeSi)，并用电弧熔炼的方法成功地在高温下合成了该相。用粉末和单晶X射线衍射法确定了高温六方相的晶体结构。经电弧炉熔炼后的样品，TiFeSi晶化为空间群为Ima2的正交结构。系统的磁学表征表明，非中心对称的正交α-TiFeSi相具有铁磁性质，在低温下可能存在螺旋磁有序。此外，为了与中心对称情况相比较，我们还用密度泛函理论和实验磁测量方法研究了反铁磁性TiNiSi型MFeSi(M=0.2Hr和0.1Hf)化合物的电磁性质。
The intertwisted helix framework of the chiral FeSi-type structure with the space groupP213 (S.G.P213) inspired us to investigate other non-centrosymmetric compounds, particularly 111-type phases with different FeSi frameworks. Various FeSi-containing 111-type phases have been summarized according to their valence electron counts and space group. In this work we have focused on the non-centrosymmetric TiFeSi phase. The crystal structure analysis of the hexagonal Fe2P-type and the reported orthorhombic TiFeSi-type (α-TiFeSi) indicate a superlattice relationship exists between the two structures, which drove us to perform the total energy calculations of the hexagonal and orthorhombic models of TiFeSi. Following the theoretical predictions, a hexagonal TiFeSi phase (β-TiFeSi) is proposed and successfully synthesized at high temperature using arc melting. The crystal structure of the high-temperature hexagonal phase was determined by powder and single crystal X-ray diffraction. After the annealing of the arc-melted samples, TiFeSi crystallizes into an orthorhombic structure with the space groupIma2. The systematic magnetic characterizations indicate ferromagnetic properties are present in the non-centrosymmetric orthorhombic α-TiFeSi phase with possible helical magnetic ordering at low temperatures. Moreover, to compare with the centrosymmetric cases, the electronic and magnetic properties of the antiferromagnetic TiNiSi-type MFeSi (M = Zr and Hf) compounds were also examined using both density functional theory and experimental magnetic measurements.