We present an extensive powder and single-crystal neutron scattering investigation of the crystallographic structure and magnetic order of the frustrated metallic $f$-electron magnet UNi$_4$B. We carry out a full refinement of the crystallographic structure and conclude that the low-temperature lattice symmetry is orthorhombic (space group Pmm2; cell parameters: $a = 6.963(4)~Å$ , $b = 14.793(9)~Å$ , $c = 17.126(8)~Å$). We determine the magnetically ordered structure, concluding that below $T_\mathrm{N} = 19.5~\mathrm{K}$ the material undergoes a transition into a partially ordered antiferromagnetic state. The magnetic structure is consistent with the existence of toroidal order in this material. We further test the proposal of a second magnetic transition occurring at $330~\mathrm{mK}$, concluding that the thermodynamic anomalies observed at these temperatures do not reflect modifications of the magnetic structure. Our study provides a consistent picture of the interrelationship of structural and magnetic properties in the frustrated magnet UNi$_4$B previously unresolved.
Local atomic and magnetic structure of dilute magnetic semiconductor (Ba,K)(Zn,Mn)$_2$As$_2$
通过对含温X射线和中子全散射数据的原子和磁对分布函数分析,研究了稀磁半导体系统(Ba,K)(Zn,Mn)$_2$ As $_2$的原子和磁结构.我们检测到的曲率变化的温度依赖性的平均tetraxite晶体结构的晶胞体积的温度与铁磁秩序的发病相一致。我们还观察到存在一个定义良好的本地正交结构上的短长度尺度的$\lesssim 5$的,导致在一个相当不对称的本地环境的Mn和As离子。最后,磁性PDF揭示了Mn自旋沿晶体学$c$轴的铁磁排列,具有甚至在铁磁有序温度以上存在的鲁棒最近邻铁磁相关性。我们讨论了这些结果的背景下,其他实验和理论研究这个系统。
Quasi two dimensional magnetic structure of the triclinic double perovskite Ca$_2$CuWO$_6$
University College London(伦敦大学学院);Durham University(杜伦大学);STFC Rutherford Appleton Laboratory(STFC卢瑟福阿普尔顿实验室);National Institute for Materials Science (NIMS)(国立材料研究所);Hokkaido University(北海道大学)
Complex magnetic structure in Ba5Ru3O12 with isolated Ru3O12-trimer
我们报告详细的磁性,运输,热容,和中子衍射测量Ba 5 Ru 3 O 12,一种化合物,由孤立的Ru 3 O 12三聚体。我们发现,该系统开发远程反铁磁有序在60 K(TN)没有结构畸变和金属-绝缘体型转变,这是在形成鲜明对比的其他钌酸钡三聚体系统,如9 R-BaRuO 3和Ba 4 Ru 3 O 10。揭示了一个复杂的磁性结构,这是由于竞争交换Ru离子之间的相互作用在不同的晶体学网站内的Ru 3 O 12三聚体的磁挫折。
Magnetic structure of the antiferromagnetic Kondo lattice compounds CeRhAl4Si2 and CeIrAl4Si2
用中子粉末衍射研究了反铁磁近藤晶格化合物CeMAl $_{4}$ Si $_{2}$(M = Rh,Ir)的磁基态。尽管这两种化合物在体相性质测量中显示出两个磁性跃迁$T_{N1}$和$T_{N2}$,但磁性长程有序的证据仅在较低的跃迁$T_{N2}$以下发现。衍射轮廓的分析揭示了一个相称的反铁磁结构的传播矢量$\mathbf{k}$ =(0,0,1/2)。CeRhAl $_{4}$ Si $_{2}$和CeIrAl $_{4}$ Si $_{2}$有序态的磁矩分别为1.14(2)和1.41(3)$μ_{B}$/Ce,并平行于结晶学$c$轴,与磁化率测量结果一致。
A new ferromagnetic semiconductor system of Eu$_{1-x}$Sr$_x$AgP $(x = 0.0-0.6)$ compounds: Crystallographic, magnetic, and magneto-resistive properties
Crystal Growth and Anisotropic Magnetic Properties of Quasi-2D (Fe$_{1-x}$Ni$_{x}$)$_{2}$P$_{2}$S$_{6}$
我们报道了准二维磁体(Fe $_{1-x}$ Ni $_x$)$_2$ P $_2$ S $_6$ with $x_\textrm{Ni} = \textrm{0, 0.3, 0.5, 0.7, 0.9 & 1}$的化学气相输运晶体生长以及彻底的结构和磁性表征。所生长的晶体表现出层状形态,在平行于空间群$C2/m$(No.12)中的单斜结构的结晶$ab$平面的层之间具有弱的范德华相互作用。磁化强度测量揭示了反铁磁基态所有生长的晶体。在有序状态下,沿不同晶向的磁化强度与$0 \leq x \leq 0.9$的伊辛各向异性一致,只有Ni $_2$ P $_2$ S $_6$的行为与各向异性海森堡或XXZ模型描述一致.在临界Ni浓度下各向异性的这种显著突变与$T_\textrm{max}$周围磁化强度最大值宽度的变化相耦合。此外,所有中间体化合物$0 < x \leq 0.9$都表现出与母体化合物Fe $_2$ P $_2$ S $_6$类似的顺磁状态的各向异性磁化。
Investigation of the oxohalogenide Cu4Te5O12Cl4 with weakly coupled Cu(II) tetrahedra
铜(II)碲(IV)氯氧化物Cu $_{4}$ Te $_{5}$ O $_{12}$ Cl $_{4}$(Cu-45124)的晶体结构是由弱耦合四面体Cu原子簇组成的,并显示出与深入研究的化合物Cu $_{2}$ Te $_{2}$ O $_{5}$ X $_{2}$(Cu-2252)的晶体学相似性,X = Cl,Br.它与后者的不同之处在于晶体学ab平面内四面体的较大分离,这允许更直接地分配重要的四面体间交换路径和反转中心的存在。磁化率和比热证明了反铁磁、Cu自旋矩的受抑关联和长程有序,$T_{c}$ =13.6 K。与跃迁相关的熵由于量子涨落而减少。在拉曼散射中,在能量为$\approx$ 50 K(35 cm $^{-1})$)处观察到结构良好的低能磁激发。与Cu-2252相比,该能量标度降低。
Topological classification under nonmagnetic and magnetic point group symmetry: Application of real-space Atiyah-Hirzebruch spectral sequence to higher-order topology