β‐Ag3RuO4, a Ruthenate(V) Featuring Spin Tetramers on a Two‐Dimensional Trigonal Lattice

Open‐shell solids exhibit a plethora of intriguing physical phenomena that arise from a complex interplay of charge, spin, orbital, and spin‐state degrees of freedom. Comprehending these phenomena is an indispensable prerequisite for developing improved functional materials. This type of understanding can be achieved, on the one hand, by experimental and theoretical investigations into known systems, or by synthesizing new solids displaying unprecedented structural and/or electronic features. β‐Ag₃RuO₄ may serve as such a model system because it possesses a remarkable anionic structure, consisting of tetrameric polyoxoanions (Ru₄O₁₆)^12?, and is an embedded fragment of a 2D trigonal MO₂ lattice. The notorious frustration of antiferromagnetic (AF) exchange couplings on such lattices is thus lifted, and instead strong AF occurs within the oligomeric anion, where only one exchange path remains frustrated among the relevant six. The strong magnetic anisotropy of the [Ru₄O₁₆]^12? ion, and the effectively orbital nature of its net magnetic moment, implies that this anion may reveal the properties of a single‐molecule magnet if well‐diluted in a diamagnetic matrix.     

基于End-On叠氮桥联的混合价Co(Ⅱ/Ⅲ)和一维Cu(Ⅱ)链-席夫碱化合物的合成、结构及磁学性质

合成了2个化合物[Co^ⅡCo₄^Ⅲ（salhn）₄（N₃）₆（CH₃OH）₂（H₂O）₂]·4CH₃OH·2H₂O （1）和[Cu₂（salhn）（N₃）₂]_n（2）（H₂salhn=N,N''-bis （salicylidene） hydrazine）,并用X射线单晶衍射进行结构表征。化合物1是一个五核的[Co^ⅡCo₄^Ⅲ]钴簇,而化合物2是一个具有结构单元为[Cu₂（salhn）（N₃）₂]的一维链结构。2个化合物中叠氮均具有end-on （EO,μ-1,1）的配位模式。化合物1和2的磁学性质测试表明它们都具有反铁磁行为。     

Crystal growth and magnetic behavior of R6T13−xAlxMy phases (R=La, Nd; T=Mn, Fe; M=main group) grown from lanthanide-rich eutectic fluxes

Binary eutectic mixtures of early lanthanide metals and late transition metals have been explored as media for crystal growth of new intermetallic phases. A large family of R₆T_13−xAl_xM_y phases (R=La or Nd; T=Fe or Mn; M=main group elements) with the La₆Co₁₁Ga₃ structure type can be crystallized from La/Ni and Nd/Fe eutectics. The tetragonal structure of these compounds features slabs of transition metal atoms capped with mixed T/Al sites and separated by layers of lanthanide ions. The growth of large crystals of the lanthanum analogs allows for the study of the anisotropic magnetic properties of the transition metal slabs. For La₆Fe_13−xAl_xM_y analogs, these order antiferromagnetically with T_N strongly dependent on the Fe/Al ratio on the mixed sites. Growth of Mn analogs is reported for the first time; the transition metal slabs in La₆(Mn/Ni)₁₀Al₃ phases order ferromagnetically with a T_C of 200 K.     

Dynamical signatures of the one-dimensional deconfined quantum critical point

We study the critical scaling and dynamical signatures of fractionalized excitations at two different deconfined quantum critical points (DQCPs) in an S = 1/2 spin chain using the time evolution of infinite matrix product states. The scaling of the correlation functions and the dispersion of the conserved current correlations explicitly show the emergence of enhanced continuous symmetries at these DQCPs. The dynamical structure factors in several different channels reveal the development of deconfined fractionalized excitations at the DQCPs. Furthermore, we find an effective spin-charge separation at the DQCP between the ferromagnetic (FM) and valence bond solid (VBS) phases, and identify two continua associated with different types of fractionalized excitations at the DQCP between the X-direction and Z-direction FM phases. Our findings not only provide direct evidence for the DQCP in one dimension but also shed light on exploring the DQCP in higher dimensions.     

Canted antiferromagnet superimposed on a buckled kagomé network in RbMn4(PO4)3

Rubidium tetramanganese tris(phosphate), RbMn₄(PO₄)₃, has been synthesized as single crystals under hydrothermal conditions. The crystal structure was refined in the space group Pnnm (D_2h¹²). It is argued that the size factor R_M/R_A, i.e. the ratio of the A⁺ ionic radius to the M²⁺ ionic radius, within the morphotropic series AM₄(TO₄)₃ corresponds to a specific type of crystal structure. At low temperatures, the antiferromagnet superimposed on a buckled kagomé network in RbMn₄(PO₄)₃ experiences a transition into a long‐range ordered state with finite spontaneous magnetization. First principles calculations provide the dominant magnetic exchange interactions both within and between the kagomé layers. The analysis of these interactions allows us to suggest a model of alternating ferromagnetic and antiferromagnetic arrangements within chains of Mn3 atoms.     

α-SUBSTITUIERTE PHOSPHONATE 62.1 TRIETHOXYPHOSPHONIUM-YLIDE BZW.-BETAINE AUS TRIETHYLPHOSPHIT UND 7-PHOSPHORYLCHINONMETHIDEN,SYNTHESE UND REAKTIVITÄT

Abstract

Durch Addition von Triethylphosphit (TEP) an die 7-Diethylphosphono- bzw. 7-Diphenylphosphinyl-3,5-di-tert.-butyl-chinonmethide 4a,b entstehen nicht die erwarteten Phosphonium-betaine 13a,b son-dern unter Protonenwanderung die überraschend stabilen Triethoxyphosphonium-ylide 14a,b. Das aus TEP und 7,7-Bisphosphonochinonmethid 6a erwartete Phosphoniumbetain 18 war unstabil und gab sofort unter Ethylenabspaltung und Protonentransfer das 4-Hydroxyaryl-trisphosphonat 7.

By addition of triethylphosphit (TEP) to the 7-diethylphosphono- or 7-diphenylphosphinyl-3,5-di-tert.-butyl-quinone methides 4a,b are formed by proton transfer, the surprisingly stable triethoxyphosphonium ylides 14a,b and not the expected phosphonium-betaines 13a,b. The phosphonium betain 18, which was expected from the reaction of TEP and the 7,7-bisphosphono-quinone methide 6a, was unstable and decomposed by proton transfer and splitting off ethylen to the 4-hydroxyaryl-trisphosphonate 7.     

Coordination chemistry of a new tetranucleating 26-membered polyaza macropolycyclic ligand and a novel phenolate/phthalazine-bridged copper(II) and zinc(II) complexes

The novel phenol and phthalazine-based symmetric compartmental 26-membered polyaza macropolycyclic ligand LH₂, was synthesised, incorporating 2,6-diformyl-p-cresol and 1,4-dihydrazinophthalazine via 1:1 condensation. Its coordination behaviour with Cu^II and Zn^II ions was investigated. The tetranuclear complexes [M₄μ(Cl₂)(L)Cl₄]·2H₂O exhibited aremarkably high stability, suggesting that, along with the large number of nitrogen donors available for metal binding, deprotonated phenolic functions were also involved in binding the metal ion. Incorporation of the bridging units into the macrocyclic cavity influenced electronic communications between the metal ions.     

Magnetic Behavior of R2Ba2CuPtO8 Oxides (R=Ho, Er, Tm, Yb, Lu, and Y)

Magnetic properties of polycrystalline R₂Ba₂CuPtO₈ (R=Ho, Er, Tm, Yb, Lu and Y) oxides have been studied from magnetization and magnetic susceptibility measurements. The lutetium and yttrium oxides behave as antiferromagnets and the estimated Néel temperatures are 5.2 and 5.7 K, respectively. In the case of the remaining R₂Ba₂CuPtO₈ oxides, Cu²⁺ and R³⁺ become antiferromagnetically ordered simultaneously, with the exception of TmBa₂CuPtO₈, where the χ vs T plot exhibits two maxima at 8 and 5 K, which have been assigned to the Néel temperatures of Cu²⁺ and Tm³⁺ sublattices, respectively. Taking into account the structure, a superexchange mechanism of the type R-O-Cu-O-R has been proposed in which the Cu²⁺ sublattice plays an important role as promoter of the antiferromagnetic interactions of ferromagnetically R³⁺ coupled in the a-c plane of the structure. Field-induced metamagnetic transitions have been observed below the Néel temperature in all cases; however, different critical fields are achieved depending on the nature of R³⁺ ions.     

Three‐Dimensional Antiferromagnetic Order of Single‐Chain Magnets: A New Approach to Design Molecule‐Based Magnets

Two one‐dimensional compounds composed of a 1:1 ratio of Mn^III salen‐type complex and Ni^II oximato moiety with different counter anions, PF₆^? and BPh₄^?, were synthesized: [Mn(3,5‐Cl₂saltmen)Ni(pao)₂(phen)]PF₆ ( 1 ) and [Mn(5‐Clsaltmen)Ni(pao)₂(phen)]BPh₄ ( 2 ), where 3,5‐Cl₂saltmen^2?=N,N′‐(1,1,2,2‐tetramethylethylene)bis(3,5‐dichlorosalicylideneiminate); 5‐Clsaltmen^2?=N,N′‐(1,1,2,2‐tetramethylethylene)bis(5‐chlorosalicylideneiminate); pao^?=pyridine‐2‐aldoximate; and phen=1,10‐phenanthroline. Single‐crystal X‐ray diffraction study was carried out for both compounds. In 1 and 2 , the chain topology is very similar forming an alternating linear chain with a [‐Mn^III‐ON‐Ni^II‐NO‐] repeating motif (where ‐ON‐ is the oximate bridge). The use of a bulky counteranion, such as BPh₄^?, located between the chains in 2 rather than PF₆^? in 1 , successfully led to the magnetic isolation of the chains in 2 . This minimization of the interchain interactions allows the study of the intrinsic magnetic properties of the chains present in 1 and 2 . While 1 and 2 possess, as expected, very similar paramagnetic properties above 15 K, their ground state is antiferromagnetic below 9.4 K and paramagnetic down to 1.8 K, respectively. Nevertheless, both compounds exhibit a magnet‐type behavior at temperatures below 6 K. While for 2 , the observed magnetism is well explained by a Single‐Chain Magnet (SCM) behavior, the magnet properties for 1 are induced by the presence in the material of SCM building units that order antiferromagnetically. By controlling both intra‐ and interchain magnetic interactions in this new [Mn^IIINi^II] SCM system, a remarkable AF phase with a magnet‐type behavior has been stabilized in relation with the intrinsic SCM properties of the chains present in 1 . This result suggests that the simultaneous enhancement of both intrachain (J) and interchain (J′) magnetic interactions (with keeping J ? J′), independently of the presence of AF phase might be an efficient route to design high temperature SCM‐based magnets.     

Quasi‐particle peak due to magnetic order in strongly correlated electron systems

We study the electron spectral function of the antiferromagnetically ordered phase of the three dimensional Hubbard model, using recently formulated low‐energy theory based on the 2D half‐filled Hubbard model which describes both collective spin and charge fluctuations for arbitrary value of the Coulomb repulsion U. The model then is solved by a saddle‐point approximation within the CP¹ representation for the Neel field. The single‐particle properties are obtained by writing the fermion field in terms of a U(1) phase, Schwinger boson SU(2) fields and a pseudofermion variables. We demonstrate that the appearance of a sharp peak in the electron spectral function in the antiferromagnetic state points to the emergence of the bosonic mode, which is associated with spin ordering.