Wenbin Guo

Syntheses and magnetic properties of new tellurite-sulfate compounds M2(TeO3)(SO4)·H2O (M = Co, Mn) with a layer structure showing a distorted honeycomb spin-lattice.

New tellurite-sulfate compounds M2(TeO3)(SO4)·H2O (M = Co, Mn) are synthesized by a conventional hydrothermal method. Two compounds are found to exhibit a similar structure, which both crystallize in the orthorhombic system of space group Pbcm. Te(4+) ions are coordinated by three O atoms, forming a quite distorted TeO3 trigonal pyramid with lone-pair electrons, while magnetic Co(2+) or Mn(2+) ions construct a wavelike layer with a distorted honeycomb spin-lattice. Magnetic measurements confirm that two isostructural compounds display different magnetic behaviors, in which Co2(TeO3)(SO4)·H2O shows a canted antiferromagnetic ordering at ∼15 K, while Mn2(TeO3)(SO4)·H2O shows a collinear antiferromagnetic ordering at ∼28 K. The nature of different magnetic behaviors between two isostructural compounds is also discussed.

Synthesis, Structure, and Magnetic Properties of A2Cu5(TeO3)(SO4)3(OH)4 (A = Na, K): The First Compounds with a 1D Kagomé Strip Lattice

Two new tellurite-sulfates A2Cu5(TeO3)(SO4)3(OH)4 (A = Na, K) have been synthesized by a conventional hydrothermal method. Both compounds feature 1D kagomé strip structure built by distorted CuO6 octahedra, which can be regarded as the dimensional reduction of kagomé lattice. Magnetic measurements confirmed that the titled compounds possess antiferromagnetic ordering at low temperature, while a field-induced magnetic transition can be observed at critical field. To the best of our knowledge, this is the first time to obtain distorted kagomé strip compounds.

A frustrated ferrimagnet Cu5(VO4)2(OH)4 with a 1/5 magnetization plateau on a new spin-lattice of alternating triangular and honeycomb strips

Cu5(VO4)2(OH)4 (turanite) is a layered compound, exhibiting a copper(II) oxide layer in the [0 1 1] plane composed of edge-sharing CuO6 octahedra. Each Cu-O layer is further separated by VO4 tetrahedra. Closer scrutiny found that the copper(II) oxide layer in the compound represents a totally new geometrically-frustrated lattice, a 1/6 depleted triangular lattice. More specifically, the spin network in the [0 1 1] plane is formed by the alternate ranking of triangular and honeycomb strips. Magnetic measurements show that the Cu5(VO4)2(OH)4 behaves as a spin-1/2 ferrimagnet with a Tc = ∼4.5 K. It exhibits an unusual 1/5 magnetization plateau arising from the competition between antiferromagnetic and ferromagnetic interactions caused by the strong frustration. The possible spin-arrangements are also suggested.

Synthesis, structure and magnetic properties of hydroxychlorides A3Cu3(OH)Cl8 (A = Cs, Rb) with isolated tricopper

Two copper hydroxychlorides, A3Cu3(OH)Cl8 (A = Cs, Rb), were synthesized by a hydrothermal method, which crystallize in the space group P21/c. All copper atoms are coordinated with three Cl atoms and one OH group forming quite distorted squares of CuCl3(OH), which further share one edge and one corner to form an isolated triangle unit of [Cu3(OH)Cl8]3− with μ2-Cl and μ3-OH cores. Interestingly, the two isostructural compounds exhibit antiferromagnetic ordering at low temperature and the dominant exchange coupling in the isolated triangle is found to be of ferromagnetic type, ruling out geometrical frustration effects. The origin of such a ferromagnetic interaction is suggested to arise likely from the folded [Cu(2)Cu(3)(OH)Cl5]2− dimers with a Cu(2)–Cl(5)–Cu(3) route.

Octa-Kagomé Lattice Compounds Showing Quantum Critical Behaviors: Spin Gap Ground State versus Antiferromagnetic Ordering

Search for a new geometrically frustrated lattice is a great challenge. Herein, we report on a successful synthesis of two new layered compounds BiOCu2(XO3)(SO4)(OH)·H2O [X = Te (1) and Se (2)] with a new type of geometrically frustrated lattice (i.e., the octa-kagomé lattice) between kagomé and star motifs. Magnetic measurements confirmed that 1 exhibits a spin gap ground state, while 2 possesses a typical antiferromagnetic ordering at low-temperature. Such different magnetic behaviors between two isostructural compounds are suggested to originate from a slightly structural modification induced by nonmagnetic XO3 anionic groups. Theoretical simulations suggest that the origin of gapped ground state in 1 may be due to the dimerization of Cu2+ ions, while 2 may break the limiting of such dimerization, leading to an antiferromagnetic ordering.

Spin-frustration in a new spin-1/2 oxyfluoride system (Cu13(VO4)4(OH)10F4) constructed by alternatively distorted kagome-like and triangular lattices

A novel copper compound, Cu13(VO4)4(OH)10F4, featuring two types of two-dimensional extended kagome-like and triangular lattices, exhibits long-range antiferromagnetic ordering at ∼3 K, a strong spin-frustration effect with f = 21 and a spin-flop transition at 5 T.

KNa3Mn7(PO4)6: 2D spin-frustrated magnetic material with a diamond-like chain structure

The search for spin frustrated magnets has attracted great scientific interest. Here we report on the synthesis of a novel two dimensional spin-frustrated compound KNa3Mn7(PO4)6 with a diamond-like chain structure. Our results confirm spin freezing at Tc = 3.9(1) K with the Weiss constant θ = −64.1(2) K, showing a remarkable spin frustration effect in the system. The origin of spin frustration is also suggested.

Layered Cu7(TeO3)2(SO4)2(OH)6 with Diluted Kagomé Net Containing Frustrated Corner-Sharing Triangles

The half-spin Kagomé antiferromagnet is one of the most promising candidates for the realization of a quantum spin liquid state because of its inherent frustration and quantum fluctuations. The search for candidates for quantum spin liquids with novel spin topologies is still a challenge. Herein, we report a new diluted Kagomé lattice in Cu7(TeO3)2(SO4)2(OH)6, showing a 9/16-depleted triangle lattice, where the corner-sharing triangle units [Cu5(OH)6O8] are separated by CuO2(OH)2. Magnetic measurements show that the title compound does not exhibit long-range antiferromagnetic order down to 2 K, suggesting strong spin frustration with f > 19.

Syntheses, structure and magnetic properties of two vanadate garnets Ca{sub 5}M{sub 4}V{sub 6}O{sub 24} (M=Co, Ni)

Two vanadate compounds Ca{sub 5}M{sub 4}V{sub 6}O{sub 24} (M=Co, Ni) have been synthesized by a high-temperature solid-state reaction. The compounds are found to crystallize in the cubic system with a space group Ia-3d, which exhibit a typical garnet structural framework. Magnetic measurements show that Ca{sub 5}M{sub 4}V{sub 6}O{sub 24} (M=Co, Ni) exhibit similar magnetic behaviors, in which Ca{sub 5}Co{sub 4}V{sub 6}O{sub 24} possesses an antiferromagnetic ordering at T{sub N}=~6 K while Ca{sub 5}Ni{sub 4}V{sub 6}O{sub 24} shows an antiferromagnetic ordering at T{sub N}=~7 K. - Graphical abstract: Garnet vanadate compounds Ca{sub 5}M{sub 4}V{sub 6}O{sub 24} (M=Co, Ni) have been synthesized by a high-temperature solid-state reaction. Structural features and magnetic behaviors are also investigated. - Highlights: • New type of garnet vanadates Ca{sub 5}M{sub 4}V{sub 6}O{sub 24} (M=Co, Ni) are synthesized by a high-temperature solid-state reaction. • Structural features are confirmed by single crystal samples. • Magnetic behaviors are firstly investigated in the systems.