Crystal Growth and Study of Unusual Magnetic Anomalies of a Low-Dimensional Iron(III) Oxy-Arsenates:

Our most recent studies have been directed towards the synthesis of low-dimensional magnetic materials as these have drawn continued attention in condensed matter chemistry and physics, owing to their diverse electronic and magnetic properties. One example of such a family is A2Fe2O(AsO4)2 where A = K, Rb. Further, the A2Fe2O(AsO4)2 series show interesting magnetic anomalies regarding stepped magnetization. Also intriguing are the negative magnetizations observed below the ordering temperature in the field cooling (FC) and zero field cooling (ZFC) susceptibility measurements. We have performed the neutron powder diffraction (NPD) measurements using HB-2A in Oakridge National Lab and BT-1 in NIST. Neutron powder diffraction for A2Fe2O(AsO4)2 were collected at various temperatures ranging from 3.3 K to 35 K. The 35 K data has been adequately described with a nuclear model, previously determined using single crystal X-ray diffraction, indicating a lack of long-range magnetic order. The NPD measurements were also conducted in horizontal fields up to 5 T at 2 K. The field dependence of the spin arrangement was used to explain the negative magnetization observed in A2Fe2O(AsO4)2. The neutron scattering measurements of K2Fe2O(AsO4)2 were also carried out using SEQUOIA—Fine-Resolution Fermi Chopper Spectrometer in ORNL

Hidden local symmetry breaking in a kagome-lattice magnetic Weyl semimetal

Exploring the relationship between intriguing physical properties and structural complexity is a central topic in studying modern functional materials. Co$_{3}$Sn$_{2}$S$_{2}$, a new discovered kagome-lattice magnetic Weyl semimetal, has triggered intense interest owing to the intimate coupling between topological semimetallic states and peculiar magnetic properties. However, the origins of the magnetic phase separation and spin glass state below $T_{C}$ in this ordered compound are two unresolved yet important puzzles in understanding its magnetism. Here, we report the discovery of local symmetry breaking surprisingly co-emerges with the onset of ferromagnetic order in Co$_{3}$Sn$_{2}$S$_{2}$, by a combined use of neutron total scattering and half polarized neutron diffraction. The mismatch of local and average symmetries occurs below $T_{C}$, indicating that Co$_{3}$Sn$_{2}$S$_{2}$ evolves to an intrinsically lattice disordered system when the ferromagnetic order is established. The local symmetry breaking with intrinsic lattice disorder provides new understandings to the puzzling magnetic properties. Our density function theory calculation indicates that the local symmetry breaking is expected to reorient local ferromagnetic moments, unveiling the existence of the ferromagnetic instability associated with the lattice instability. Furthermore, DFT calculation unveils that the local symmetry breaking could affect the Weyl property by breaking mirror plane. Our findings highlight the fundamentally important role that the local symmetry breaking plays in advancing our understanding on the magnetic and topological properties in Co$_{3}$Sn$_{2}$S$_{2}$, which may draw the attention to explore the overlooked local symmetry breaking in Co$_{3}$Sn$_{2}$S$_{2}$, its derivatives, and more broadly in other topological Dirac/Weyl semimetals and kagome-lattice magnets.Comment: 35 pages, 6 figures, 1 table, 1 Supplementary Informatio

CSD 1789298: Experimental Crystal Structure Determination

Related Article: Liurukara D. Sanjeewa, Michael A. McGuire, Vasile O. Garlea, Longyu Hu, George Chumanov, Colin D. McMillen, Joseph W. Kolis|2015|Inorg.Chem.|54|7014|doi:10.1021/acs.inorgchem.5b01037,An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures

CCDC 1567344: Experimental Crystal Structure Determination

Related Article: Liurukara D. Sanjeewa, Vasile O. Garlea, Michael A. McGuire, Matthias Frontzek, Colin D. McMillen, Kyle Fulle, Joseph W. Kolis|2017|Inorg.Chem.|56|14842|doi:10.1021/acs.inorgchem.7b02024,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures

CSD 1789296: Experimental Crystal Structure Determination

Related Article: Liurukara D. Sanjeewa, Michael A. McGuire, Vasile O. Garlea, Longyu Hu, George Chumanov, Colin D. McMillen, Joseph W. Kolis|2015|Inorg.Chem.|54|7014|doi:10.1021/acs.inorgchem.5b01037,An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures

CCDC 1567343: Experimental Crystal Structure Determination

Related Article: Liurukara D. Sanjeewa, Vasile O. Garlea, Michael A. McGuire, Matthias Frontzek, Colin D. McMillen, Kyle Fulle, Joseph W. Kolis|2017|Inorg.Chem.|56|14842|doi:10.1021/acs.inorgchem.7b02024,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures

CSD 1789297: Experimental Crystal Structure Determination

Related Article: Liurukara D. Sanjeewa, Michael A. McGuire, Vasile O. Garlea, Longyu Hu, George Chumanov, Colin D. McMillen, Joseph W. Kolis|2015|Inorg.Chem.|54|7014|doi:10.1021/acs.inorgchem.5b01037,An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures

CSD 1789299: Experimental Crystal Structure Determination

Related Article: Liurukara D. Sanjeewa, Michael A. McGuire, Vasile O. Garlea, Longyu Hu, George Chumanov, Colin D. McMillen, Joseph W. Kolis|2015|Inorg.Chem.|54|7014|doi:10.1021/acs.inorgchem.5b01037,An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures

Crystal field levels and magnetic anisotropy in the kagome compounds Nd3Sb3Mg2 O14, Nd3Sb3Zn2 O14, and Pr3Sb3Mg2 O14

Physical Review B Volume 98, Issue 13, 1 October 2018, Article number 134401© 2018 American Physical Society. We report the crystal field levels of several newly discovered rare-earth kagome compounds: Nd3Sb3Mg2O14, Nd3Sb3Zn2O14, and Pr3Sb3Mg2O14. We determine the crystal electric field (CEF) Hamiltonian by fitting to neutron scattering data using a point charge Hamiltonian as an intermediate fitting step. The fitted Hamiltonians accurately reproduce bulk susceptibility measurements, and the results indicate easy-axis ground-state doublets for Nd3Sb3Mg2O14 and Nd3Sb3Zn2O14 and a singlet ground state for Pr3Sb3Mg2O14. These results provide the groundwork for future investigations of these compounds and a template for CEF analysis of other low-symmetry materials

Polar Materials with Isolated V⁴⁺ <i>S</i> = 1/2 Triangles: NaSr₂V₃O₃(Ge₄O₁₃)Cl and KSr₂V₃O₃(Ge₄O₁₃)Cl

Crystals of ASr₂V₃O₃(Ge₄O₁₃)­Cl, A = Na, K, were synthesized from high-temperature hydrothermal brines, and their structure and magnetic properties were investigated. These materials present a unique combination of a salt inclusion lattice, a polar crystal structure, and isolated V⁴⁺ (<i>S</i> = 1/2) trimer magnetic clusters. The structures consist of a trimeric V₃O₁₃ unit based on V⁴⁺ (<i>S</i> = 1/2), having rigorous 3-fold symmetry with a short V–V separation of 3.325(3) Å. The trinuclear V⁴⁺ units are formed by three edge shared VO₆ octahedra sharing a central μ₃-oxygen atom, which also imparts a polar sense on the structure. The V₃O₁₃ units are isolated from one another by tetranuclear Ge₄O₁₃ units, which are similarly arranged in a polar fashion, providing a unique opportunity to study the magnetic behavior of this triangular <i>d</i>¹ system as a discrete unit. Magnetization measurements indicate spin-1/2 per V atom at high temperature, and spin-1/2 per V₃ trimer at low temperature, where two V moments in each triangle are antiferromagnetically aligned and the third remains paramagnetic. The crossover between these two behaviors occurs between 20 and 100 K and is well-described by a model incorporating strong antiferromagnetic intra-trimer interactions and weak but nonzero inter-trimer interactions. More broadly, the study highlights the ability to obtain new materials with interesting structure–property relationships via chemistry involving unconventional solvents and reaction conditions