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A family of oxygen coordinated dichlorido-bridged n-X-2-pyridone (1, n = 3, X = Cl; 2, n = 3, X = Br; 3, n = 4, X = Cl; 4, n = 4, X = Br; 5, n = 5, X = Cl; 6, n = 5, X = Br) Cu(II) offset stacked dimer compounds, denoted molecular spin stairs, have been prepared and analyzed by single-crystal X-ray diffraction (1–4), powder X-ray diffraction (1–6), and variable temperature magnetic susceptibility measurements (1–6). Ferromagnetism is dominant in all compounds with a weaker antiferromagnetic exchange present in 1–4. The ferromagnetic exchange correlates to increased twist angles which are defined by the extent of the tetrahedral distortion of the copper coordination sphere and the identity of the halogen on the ring. The compounds were qualitatively fit to a ferromagnetic Heisenberg chain model with a Curie-Weiss interchain correction. The general Hamiltonian used is of the form H = − J ∑ S 1 S 2 . The ratio of exchange energies denoted α (α = J FM | J AFM | ) ranges between 2.6 and 4.7. This family of compounds constitutes possible S = ½ Haldane-like materials. [ABSTRACT FROM AUTHOR]

The polynuclear complex Cu 2 (naphac) 2 (OH) 2 consists of isolated Cu ladders in which square planar CuO 4 and square-pyramidal CuO 5 units are linked alternately along the crystalline a direction through their corners, and the resultant two adjacent Cu alternating chains connect each other through edges of the CuO 5 units to form a ladder. The temperature dependence of the magnetic susceptibility above 50 K is reproduced by the calculation of the spin-1/2 two-leg honeycomb spin ladder model with almost zero exchange coupling between two legs of ladder. This is explained by the Jahn-Teller elongation of square-pyramidal CuO 5 units. The absence of lambda-shaped peak in the specific heat down to 1.9 K suggests the existence of large quantum fluctuations of the spin owing to low-dimensional antiferromagnetic interactions. [ABSTRACT FROM AUTHOR]

PbCu(SeO4)(OH)2, the selenate sibling of the mineral linarite, was synthesized hydrothermally, investigated in measurements of magnetization M, specific heat Cp and dielectric permittivity ε, and analyzed within density functional theory formalism. This quasi-one-dimensional compound evidences formation of a short-range correlation regime at T* ~ 8 K and experiences a long-range magnetic order at TN = 4.3 K. A magnetization saturation of approximately 1 µB is reached at µ0Hflip ~ 16 T preceded by a jump at µ0Hflop = 2.4 T. Additionally, there are multiple indicators of the formation of an additional electrically active phase above the Neel temperature, which suggests that PbCu(SeO4)(OH)2 is a multiferroic system. [ABSTRACT FROM AUTHOR]

The van der Waals magnet CrSiTe3 (CST) has captured immense interest because it is capable of retaining the long‐range ferromagnetic order even in its monolayer form, thus offering potential use in spintronic devices. Bulk CST crystal has inversion symmetry that is broken on the crystal surface. Here, by employing ultrafast terahertz (THz) emission spectroscopy and time resolved THz spectroscopy, the THz emission of the CST crystal is investigated, which shows a strong THz emission from the crystal surface under femtosecond (fs) pulse excitation at 800 nm. Theoretical analysis based on space symmetry of CST suggests the dominant role of shift current occurring on the surface with a thickness of a few quintuple layers in producing the THz emission, consistent with the experimental observation that the emitted THz amplitude strongly depends on the azimuthal and pumping polarization angles. This study offers a new efficient THz emitter as well as a better understanding of the nonlinear optical response of CST. It hopefully will open a window toward the investigation on the nonlinear optical response in the mono/few‐layer van der Waals crystals with low‐dimensional magnetism. [ABSTRACT FROM AUTHOR]

TlCu2O2, a mixed‐valence spin‐chain cuprate, was synthesized in a piston cylinder system starting from thallium sesquioxide Tl2O3, cuprous oxide Cu2O and copper powder. The main structural characteristics are edge‐sharing (CuO2)n zigzag chains, which are linked in the perpendicular crystallographic direction by Cu+ to form a three‐dimensional network. Data from magnetic susceptibility and specific heat measurements show features typical for low‐dimensional magnetic exchange interactions. The long‐range antiferromagnetic ordering is observed at TN = 19.7 K. No weak ferromagnetic component can be detected, suggesting a plain Néel‐type spin‐ordered structure. [ABSTRACT FROM AUTHOR]

Abstract This communication focuses on recently discovered Ln 3 CrGe 3 Be 2 O 14 (Ln = La–Sm) compounds as a new class of low-dimensional magnets. We conducted the first studies of their magnetic properties by means of the magnetic susceptibility, specific heat, and high-resolution optical spectroscopy measurements of the La and Nd representatives. In La 3 CrGe 3 Be 2 O 14 , which contains only one (chromium) magnetic system, the shortest exchange paths are within isolated chromium chains along the c axis. The compound demonstrates one-dimensional magnetic behavior, i.e., an absence of a long-range order, at least down to 0.4 K, and short-range magnetic correlations with the antiferromagnetic exchange integral along the chains estimated as J Cr = 4.0 ± 0.5 K. In Nd 3 CrGe 3 Be 2 O 14 containing two magnetic subsystems, a splitting of the neodymium Kramers doublets at low temperatures indicates magnetic activity due to both short-range correlations and possible magnetic ordering at 2 K. Graphical abstract Image 1 Highlights • Langasite compound La 3 CrGe 3 Be 2 O 14 demonstrates one-dimensional magnetism. • Antiferromagnetic exchange integral along the Cr chains is 4.0 ± 0.5 K. • Splitting of Nd3+ Kramers doublets explains specific heat Schottky anomaly for Nd 3 CrGe 3 Be 2 O 14. • Nd 3 CrGe 3 Be 2 O 14 orders magnetically at 2 K. [ABSTRACT FROM AUTHOR]

Combining very low-temperature experiments such as neutron diffraction, magnetometry, and specific-heat measurements, we report on the magnetic properties of the Fe x Co 1− x Nb 2 O 6 series of compounds. This investigation demonstrates that the ground state for x = 0.2, 0.4, and 0.6, previously reported as totally frustrated, is composed of Ising-like ferromagnetic chains that are antiferromagnetically ordered. Ordering at these compositions is observed to occur below 2 K. The magnetic structure is obtained from neutron diffraction, and susceptibility measurements allow us to estimate the values of intra- and interchain exchange constants, the former being clearly dominant. Fe/Co cation disorder reduces the average exchange strength within and between chains, reflecting the tendency to suppress long-range magnetic order. The diffuse magnetic signal observed by neutron diffraction slightly above the Néel temperature is analyzed to extract information on short-range magnetic correlations. Magnetization curves at 80 mK and specific-heat measurements reveal that an external magnetic field easily breaks the antiferromagnetic order, leading to a high magnetization due to the alignment of the ferromagnetic Ising chains. • Exploring AB 2 O 6 Compounds: Investigating the structural and magnetic properties of AB 2 O 6 compounds (A = Fe, Co, Ni; B Ta, Nb) with magnetic ordering at low temperatures and diverse magnetic phases. • Unveiling Low-Dimensional Magnetism: AB 2 O 6 compounds reveal intriguing low-dimensional magnetism, driven by distinct crystal structure symmetries of niobates. • Crystal Structure Insights: ANb 2 O 6 's columbite structure showcases alternatingly tilted oxygen octahedra, forming distinctive zig-zag chains within the lattice. • Probing CoNb 2 O 6 and FeNb 2 O 6 transitions and magnetic characteristics: Investigating CoNb 2 O 6 's transition from paramagnetic to ordered spin structure at 2.95 K using a combination of neutron diffraction and magnetic measurements. Understanding the magnetic properties of FeNb 2 O 6 , highlighting collinear and noncollinear magnetic ordering phases, including the coexistence of different magnetic structures. • Detailed Fe x Co 1−x Nb 2 O 6 Study: In-depth analysis of Fe x Co 1−x Nb 2 O 6 compounds at varying Fe concentrations (x = 0.2, 0.4, 0.6) revealing magnetic ordering phenomena below 2 K. • Deciphering Short-Range Order: Identifying short-range magnetic correlations through neutron diffraction signals provides insights into the precursor states leading to ordered magnetic arrangements. • Unraveling Exchange Constants: Determination of intrachain and interchain exchange constants, emphasizing the dominance of intrachain interactions due to ferromagnetic coupling within zig-zag chains. [ABSTRACT FROM AUTHOR]

This article investigates the magnetic susceptibility, χ(T), of the two-phase (R32 + C2/c) crystal LaCr3(BO3)4 in the temperature range 2–300 K for two orientations of an external magnetic field. It has been established that both structural modifications of lanthanum chromium borate are ordered antiferromagnetically, with each of them having its own Néel temperature (6.5 and 8.5 K). It has been shown that at T > 60 K, the magnetic susceptibility is well described by the Curie–Weiss law with an effective magnetic moment of μeff = 3.86 μB/Cr3+ and a Curie–Weiss temperature of θ = –23 K. Within the Heisenberg spin chain model, taking into account the interchain exchange interaction, the authors have obtained the following exchange-interaction constants: an antiferromagnetic intrachain exchange (J/k = 4.8 K) and a ferromagnetic interchain exchange (J'/k = –0.28 K). [ABSTRACT FROM AUTHOR]

A series of Mn x Fe 1 - x Nb 2 O 6 compounds ( 0 ⩽ x ⩽ 1 ) is investigated by both X-ray and neutron powder diffraction, as well as specific-heat and magnetic measurements. The samples present orthorhombic Pbcn crystal symmetry, and exhibit weakly coupled magnetic chains. These chains are of Heisenberg type (weak anisotropy) on the Mn-rich side, and Ising-like (strong anisotropy) on the Fe-rich side. Except for 100% Fe ( x = 0 ) , which has weakly-interacting ferromagnetic Ising chains, a negative Curie-Weiss temperature is obtained from the magnetic susceptibility, indicating dominant antiferromagnetic interactions. At the lowest probed temperature, T = 1.5 K , true long-range magnetic order is only observed for x = 1 , 0.8, and 0. Although the ordering is globally antiferromagnetic in all cases, the first two are characterized by a two-sublattice structure with propagation vector k = ( 0 , 0 , 0 ) , while the latter presents alternatingly oriented ferromagnetic chains described by k = ( 0 , 1 2 , 0 ) . For other compositions, short-range magnetic correlations are extracted from diffuse neutron-scattering data. [ABSTRACT FROM AUTHOR]

La 3 TM WS 3 O 6 ( TM = Fe, Co) and novel Ba 3 CrVS 4 O 3 can be obtained as pure polycrystalline samples by mineralizer aided solid-state reactions and a solid-state reaction with further purification by water, respectively. In contrast, La 3 CrWS 3 O 6 needs a standard solid-state reaction to form but the final product contains observable impurities. All four compounds contain similar quasi-1-D magnetic lattices although La-based ones are centrosymmetric ( P 6 3 / m ) and the Ba-containing one is polar and non-centrosymmetric ( P 6 3 ). Strong antiferromagnetic couplings are observed along the magnetic chains in the Fe and Cr containing compounds. As a result, short-range magnetic order is suggested at low temperatures for the Fe-chain, which can be related to magneto-electric couplings. The Co 3+ -homologue shows typical diamagnetic behavior, as supported by its insulating nature, which is due to a low-spin state. The polar Cr 3+ -compound exhibits very different magnetic behavior compared to its corresponding non-polar relative. This proves a strong influence on the physical properties from the crystallographic symmetry. [ABSTRACT FROM AUTHOR]

A series of DyFe 1- x In x O 3 ( x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1) polycrystalline samples have been prepared by the conventional solid reaction methods. The crystal structures, refined by the Fullprof, are found to be orthorhombic for 0 ≤ x ≤ 0.6 and hexagonal in the case of 0.7 ≤ x ≤ 1. The lattice constants are changed by the In ions doping, and a huge distortion of the magnetic sublattice was induced. The magnetization versus temperature curves are obtained for all the samples, at the temperature between 3 K and 300 K. The pure DyFeO 3 sample undergoes a spin reorientation transition at around 50 K, whereas the doped In 3+ ions significantly modify the phase transition. We reveal that such substitution retained the spin reorientation transition effect for x ≤ 0.8. We develop a formalism based on the molecular theory, giving explanation of the changes in the spin-reorientation temperature induced by the In-doping. Then, by performing density functional theory (DFT) calculation, we analyzed the magnetic phases for the hexagonal compounds. Furthermore, our findings indicate a type of Γ′ 4 - Γ′ 2 transition exists in the hexagonal Fe-In magnetic systems which directly point to a quasi-2 dimensional magnetic order. [ABSTRACT FROM AUTHOR]

Highlights • High-pressure optical floating-zone Single crystal growth of Li 2 FeSiO 4 is reported. • Sharp transition to antiferromagnetic order at T N = 17.0 (5) K. • Broad maximum at T m = 28 K points to quasi-low-dimensional magnetism. • Magnetostriction anomalies at 4.2 K indicate a phase transition at B = 14.8 T. Abstract A macroscopic single crystal of γ II -Li 2 FeSiO 4 has been grown by means of the high-pressure optical floating-zone technique. Static magnetic susceptibility χ implies that the tetrahedrally-coordinated Fe 2 + ions are in the high-spin, S = 2 , state. While a sharp decrease in χ implies long-range antiferromagnetic order below T N = 17.0 (5) K , the presence of a broad maximum at T m = 28 K suggests quasi-low-dimensional magnetism. Applying magnetic fields along the easy magnetic a -axis yields additional contributions to the susceptibility ∂ M / ∂ B and magnetostriction for B > 7 T , and an anomaly at B ≈ 14.8 T. [ABSTRACT FROM AUTHOR]

An ambient-pressure solution route and an improved solvothermal synthetic method have been developed to produce polycrystalline powders and large single crystals of NH 4 MCl 2 (HCOO) (M=Fe, Co, Ni). The magnetic structure of the 1D linear chain compound NH 4 FeCl 2 (HCOO) has been determined by low-temperature neutron powder diffraction, revealing ferromagnetic intra-chain interactions and antiferromagnetic inter-chain interactions. The newly-reported Co and Ni analogs are isostructural with NH 4 FeCl 2 (HCOO), but there are significant differences in the magnetic properties of each compound; the Ni analog behaves similarly to the Fe compound but with stronger magnetic coupling, exhibiting antiferromagnetic ordering ( T N =8.5 K) and a broad metamagnetic transition between 2 and 5 T, while the Co analog does not order magnetically above 2 K, despite strong antiferromagnetic nearest-neighbor interactions. [ABSTRACT FROM AUTHOR]

We review the basic properties of the Haldane phase in spin-1 Heisenberg antiferromagnetic chains, including its persistence in quasi-one-dimensional (Q1D) geometries. Using large-scale numerical simulations, we map out the phase diagram for a realistic model applicable to experimental Haldane compounds. We also investigate the effect of different chain coupling geometries and confirm a general mean-field universality of the critical coupling times the coordination number of the lattice. Inspired by recent developments in the characterization of symmetry protected topological (SPT) states, of which the Haldane phase of the spin-1 Heisenberg antiferromagnetic chain is a preeminent example, we provide direct evidence that the Q1D Haldane phase is indeed a nontrivial SPT state. [ABSTRACT FROM AUTHOR]

• No long-range magnetic order was found in Pr 3 CrGe 3 Be 2 O 14 langasite down to 0.4 K. • Isolated 1D chains of S = 3/2 Cr3+ are situated perpendicular to 2D Kagomé -layers of Pr3+. • Crystal-field splitting of Pr3+ levels explains Schottky anomaly in specific heat. [Display omitted] We present the results of thermodynamic and optical spectroscopy measurements of the Pr 3 CrGe 3 Be 2 O 14 compound - a member of the recently discovered Be-subgroup of the langasite family. Despite the presence of both rare-earth and transition-metal subsystems in Pr 3 CrGe 3 Be 2 O 14 , no long-range magnetic order has been found down to 0.4 K in terms of both magnetization M and specific heat C p. These data are compared with those on Pr 3 AlGe 3 Be 2 O 14. Both compounds evidence the Schottky anomaly at low temperatures, most pronounced in the case of Pr 3 CrGe 3 Be 2 O 14. [ABSTRACT FROM AUTHOR]

An account of symmetry is very fruitful in studies of quantum spin systems. In the present paper we demonstrate how to use the spin SU(2) and the point symmetries in optimization of the theoretical condensed matter tools: the exact diagonalization, the renormalization group approach, the cluster perturbation theory. We apply the methods for study of Bose-Einstein condensation in dimerized antiferromagnets, for investigations of magnetization processes and magnetocaloric effect in quantum ferrimagnetic chain. [ABSTRACT FROM AUTHOR]

Abstract: Crystal structures of the Cr-based germanates: ACrGe2O6 (A =Li and Na) which show the specific magnetic properties, are solved using synchrotron powder-diffraction data at room temperature. Both compounds have isostructure which belongs to monoclinic C2/c with pyroxene-type structure. In both ACrGe2O6 structures, chromium atom forms the magnetic one-dimensional edge-shared CrO6 chain. In the NaCrGe2O6 structure, the shortest Cr⋯Cr distance and Cr–O–Cr angle are both longer and wider compared to those in the LiCrGe2O6 structure. This behavior may give strong influence to the difference of their magnetic properties. [Copyright &y& Elsevier]

A 3D model of the magnetization dynamics in frustrated triangular spin-chain systems Ca3Co2O6 is proposed. This model is a generalization of the 2D model developed earlier. The spins are assumed to interact with the nearest neighbors and external agency (heat reservoir and external magnetic field) that causes them to change their states randomly with time. A probability of a single spin-flip process is assumed in a Glauber-like form. The 3D model allows describing the step-like behavior of a magnetization curves experimentally observed in a strong magnetic field. [ABSTRACT FROM AUTHOR]

Abstract: Crystal structures and magnetic properties of metal telluromolybdates Co1− x Zn x TeMoO6 (x=0.0, 0.1,…,0.9) are reported. All the compounds have an orthorhombic structure with space group P21212 and a charge configuration of M2+Te4+Mo6+O6. In this structure, M ions form a pseudo-two-dimensional lattice in the ab plane. Their magnetic susceptibility measurements have been performed in the temperature range between 1.8 and 300K. The end member CoTeMoO6 shows a magnetic transition at 24.4K. The transition temperature for solid solutions rapidly decreases with increasing x and this transition disappears between x=0.4 and 0.5, which is corresponding to the percolation limit for the square-planer lattice. From the magnetization, specific heat, and powder neutron diffraction measurements, it is found that the magnetic transition observed in the CoTeMoO6 is a canted antiferromagnetic ordering of Co2+ ions. The antiferromagnetic component of the ordered magnetic moment (3.12(3)μ B at 10K) is along the b-axis. In addition, there exists a small ferromagnetic component (0.28(3)μ B) along the a-axis. [Copyright &y& Elsevier]

The brownmillerite-type layered compound Ca2:375La0:125Sr0:5GaMn2O8 has been synthesized. The crystal and magnetic structures have been refined by the Rietveld analysis of the neutron powder diffraction patterns at 300 and 20 K. This compound crystallizes in the orthorhombic symmetry under the space group Pcm21 (a = 5.447(2), b = 11.359(4) and c = 5.322(2) Å). The compound is found to be antiferromagnetic at 20 K. The ordered Mn magnetic moment, aligned along the crystallographic b-direction, is derived to be 2.53(5) μB per Mn ion at 20 K. [ABSTRACT FROM AUTHOR]

Abstract: We review a selection of recent applications of neutron scattering to the field of quantum magnetism. We focus on systems where, because of quantum fluctuations enhanced by frustration and low dimension, there is no long range magnetic order in the ground state. We select two examples that we treat in more depth to show how neutron studies, in conjunction with the results of other experimental techniques, can give new insights. The first is the case of the spin ladder NaV2O5, where the origin of the spin gap at low temperature is now understood in detail. Apparent contradictions between quantitative measures of the charge order from neutron inelastic scattering, resonant X-ray scattering and NMR have been resolved giving interesting insights into the correlations. The second case is that of spin dimer system Cs3Cr2 (X= Br, Cl), undergoing transitions to field induced transverse magnetic order. The Br compound is attractive as the critical fields are sufficiently low that a complete study, in different field directions, is possible. In addition, it is noteworthy in that the magnon that softens and condenses is incommensurable with the lattice. The common description in terms of Bose–Einstein condensation must be extended to include a continuous degeneracy and single ion anisotropy, and conclusions can be drawn by comparison with the Cl compound. To cite this article: B. Grenier, T. Ziman, C. R. Physique 8 (2007). [Copyright &y& Elsevier]

Abstract: The International Conference on Strongly Correlated Electron Systems 2005 in Vienna (SCES’05) has presented a host of new phenomena, new materials, new methods and new ideas, with some of the main themes including quantum criticality, superconductivity in various environments, and low-dimensional magnetism. A brief overview over key activities is given. [Copyright &y& Elsevier]

Abstract: Two aspects of low-dimensional magnetism are discussed: the spin-dependent quantization effects in perfect two-dimensional single crystal layers and the magnetic domain structure of submicron magnetic patterns. Both require high lateral resolution and surface sensitivity. This is provided by spin-polarized low energy electron microscopy (SPLEEM) and X-ray magnetic circular dichroism photoemission electron microscopy (XMCDPEEM). [Copyright &y& Elsevier]

Abstract: The magnetic properties at finite temperature of thin Fe(001) films of 1.5, 2, 2.5 and 3 monolayers (ML) are theoretically studied. The spin-polarized electronic structure at a given temperature is determined by solving self-consistently a one-particle d-band model Hamiltonian in the real space, in which correlation effects are included in a temperature-dependent spin-splitting parameter. For the half-integerML films we obtain several magnetic solutions at T =0K, most of which do not exist at finite T. An oscillatory Curie temperature (T c) as a function of film thickness is found, with larger T c for the half-integerML films. [Copyright &y& Elsevier]

Abstract: We report structural and magnetic data of a new transition metal oxide containing hexagonal planes of magnetic () ions in a 5-fold trigonal-bipyramidal coordination of oxygen ions. Static magnetic susceptibility and electron spin resonance (ESR) data as well as numerical quantum Monte-Carlo calculations suggest that Cu spins in the layers are strongly antiferromagnetically coupled with K and form a two-dimensional -Heisenberg honeycomb lattice. Owing to the appreciable interlayer coupling the compound orders magnetically at . Remarkably, ESR gives evidence that the orbital ground state of is not the orbital as in copper oxides with the usual octahedral, square-pyramidal or square-planar coordination, but it is the orbital, which is unique for the cuprates. [Copyright &y& Elsevier]

S=1/2 KCuCl3 has a singlet ground state with a finite spin energy gap Δ=31 K to triplet excited states. The bulk magnetic susceptibility vanishes for T≪Δ according to the singlet nature of the ground state. Astonishingly, recent muon spin relaxation (μSR) measurements reveal fluctuating internal fields down to T=5 K, with the onset of a quasi-static regime below T=5 K. The presence of free electronic magnetic moments and their possible freezing at low T contradicts the bulk picture of KCuCl3. By means of polarized neutron scattering and μSR measurements on single crystals of the same batch, the nature of the local spin susceptibility is studied. The claims of a substantial muon influence in KCuCl3 are reinforced. [Copyright &y& Elsevier]

The spin glass transition of the quasi-one-dimensional (1D) organic-based magnet [MnTPP]+[TCNE]− 2(1,3-C6H4Cl2) (TPP is tetraphenylporphyrin dianion, TCNE is tetracyanoethylene) is explored using both a.c. and d.c. measurements. The a.c. susceptibility shows a strong frequency dependent peak consistent with a clustered spin glass state. Application of a d.c. magnetic field suppresses the peak in the a.c. susceptibility. Magnetic relaxation data can be fit to a stretched exponential, with the results reflecting a spin glass transition near 4 K. The spin cluster dimension and the effective dimension of the system are calculated within a fractal cluster model of spin glasses with values for the spin cluster dimension ranging from ∼0.8 to over 1.5 as the glass transition is approached. [Copyright &y& Elsevier]

Cu3(OH)4SO4, obtained by hydrothermal synthesis from copper sulfate and soda in aqueous medium, is isostructural with the corresponding antlerite mineral, orthorhombic, space group Pnma (62), with a=8.289(1) b=6.079(1) and c=12.057(1) A˚, V=607.5(2) A˚3, Z=4. Its crystalline structure has been refined from X-ray single crystal and powder neutron diffraction data at room temperature. It consists of copper (II) triple chains, running in the b-axis direction and connected to each other by sulfate groups. The magnetic structure, solved from powder neutron diffraction data at 1.4 K below the transition at 5 K evidenced by susceptibility and specific measurements, reveals that, inside a triple chain, the magnetic moments of the copper ions (μB=0.88(5) at 1.4 K) belonging to outer chains are oriented along the c-axis of the nuclear cell, with ferromagnetic order inside a chain and antiferromagnetic order between the two outer chains. No long-range magnetic order is obtained along the central chain with an idle spin behavior. [Copyright &y& Elsevier]

Abstract: We have synthesized Sr2PrO4, an orthorhombic oxide (S.G. Pbam), which presents a 1D-framework of edge sharing [PrO6] octahedra forming chains along the crystallographic c-axis. These chains containing Pr4+ f1 ion are far from each other and only connected through non-magnetic [SrO6] trigonal prisms. Magnetic susceptibility measurements using a SQUID magnetometer in the temperature range from RT down to 1.7K show a net maximum at 3.4K. We performed neutron powder diffraction experiments collecting patterns at temperatures below and above that of the χ maximum and the data do not show any evidence of magnetic order, which is in contradiction with the apparent feature of bulk measurements. This anomalous behaviour could be due to the low-dimensional nature of the magnetic interactions or by a strong reduction of the rare earth magnetic moment due to the crystal field. [Copyright &y& Elsevier]

Abstract: Chirality is shown to emerge as a novel degree of freedom of a quantum soliton in the anisotropic spin- compound CsCoBr3. The soliton chirality, detected via polarized neutron scattering, is in agreement with theoretical predictions and is a manifestation of Berry''s phase. Our observations provide an explicit example of the emergence of spin currents and hidden chiral order that accompany the disappearance of antiferromagnetic order. [Copyright &y& Elsevier]

• Magnetic, magnetoelectric and thermodynamic properties of GdCr 3 (BO 3) 4 are reported. • Exchange interaction constants are estimated. • Spin-reorientation transition induced by magnetic field was found. • Magnetoelectric effect in GdCr 3 (BO 3) 4 was observed. • Magnetic phase diagram of GdCr 3 (BO 3) 4 is constructed. Comprehensive studies of magnetic properties of GdCr 3 (BO 3) 4 single crystal have been carried out. The integrals of intrachain (J / k = 4 ± 1 K) and interchain (J ΄ /k ≈ −0.7 K) exchange interactions in the Cr subsystem have been determined and the strength of Cr-Gd exchange interaction (J Cr-Gd /k ~ −0.2 K) has been estimated. The values of the exchange field 2 H E ≈ 17 T and the effective magnetic anisotropy field H A ≈ 0.05 T of GdCr 3 (BO 3) 4 have been estimated. The electric polarization Δ P a along the a axis in the longitudinal geometry of the experiment has been detected. Correlations between the electric polarization and the magnetization of the studied compound have been found. The spin-reorientation phase transition in the magnetically ordered state has been found. This transition exists for the external magnetic field applied along any crystallographic direction and the transition field depends weakly on the direction of the field. Nature of the spin-reorientation phase transition has been discussed. Magnetic phase diagram has been constructed and spin configurations for the low-field and high-field phases have been proposed. [ABSTRACT FROM AUTHOR]

• Magnetic exchange constants of CaFeF 5 and SrFeF 5 are calculated. • Strong intrachain and weaker interchain interactions are found. • Antiferromagnetic order is found at low temperatures. • SrFeF 5 is predicted to be a multiferroic. Fluorides in general are characterized by big variety of crystal structures, whereas those containing transition metals also often show sizable magnetic properties. The tendency of fluorine to form linear chain structures in many cases results in low-dimensional magnetism. Despite the plethora of magnetic phenomena in fluorides, their magnetoelectric properties are less studied than those of oxides. In the present work we theoretically study the magnetic and magnetoelectric properties of spin-chain compounds CaFeF 5 and SrFeF 5. The density functional theory is employed for determination of magnetic exchange constants, which are then used in Monte Carlo calculations. The symmetry analysis reveals that CaFeF 5 does not show magnetoelectric properties, whereas SrFeF 5 is a multiferroic. [ABSTRACT FROM AUTHOR]

Abstract: We report zero-field experiments on two samples ( and ). Muon spin rotation confirmed a magnetic ground state in both compounds, but also revealed for the stoichiometric material an ordering temperature much lower than any previously reported one. Along with the observed stabilization of magnetism in the electron-doped compound, this suggests that magnetism in the nominally undoped is essentially an extrinsic property, possibly related to slight deviations from the stoichiometry, and that the perfectly pure material is non-magnetic. [Copyright &y& Elsevier]

Abstract: Muon spin relaxation measurements around the 25K metal–insulator transition in elucidate a profound role of disorder as a possible mechanism for this transition. The relaxation rate and the muon Knight shift are incompatible with the transition to a SDW state and thus exclude it. [Copyright &y& Elsevier]

Abstract: Yamasaki et al. (Solid State Commun. 119 (2001) 415) have suggested that LaMn4Al8 is a nearly antiferromagnetic metal with linear chains of Mn atoms. We present evidence from ZF-μSR measurements that both LaMn4Al8 and the related compound PrMn4Al8 display antiferromagnetic order at low temperatures. In LaMn4Al8 the μSR relaxation rate rises to a peak at 4.5K; below this temperature the asymmetry decreases smoothly. In PrMn4Al8 well-defined oscillations appear below 35K. Neutron crystal field spectroscopy suggests a singlet ground state for the Pr3+ ion, so it is likely that the internal field seen by the muons arises from ordered Mn moments. YMn4Al8 shows no sign of magnetic correlations down to 1.2K. [Copyright &y& Elsevier]

We present susceptibility measurements on the natural mineral atacamite, Cu 2 Cl(OH) 3 , for the first time along the three crystallographic axes. Further, we have carried out an elastic neutron diffraction experiment which shows that the symmetry of the magnetic ground state of atacamite is described by a propagation vector q =(1/2 0 1/2). [ABSTRACT FROM AUTHOR]

The magnetic properties of the quasi-one-dimensional magnet AM3+Si2O6 (A=Li, Na; M=Ti, V, Cr) have been investigated in the light of the number of d-electron (spin number). The Ti(d1)-compound shows a spin-Peierls like transition at the temperature higher than that (TMAX) at the maximum point of the Bonner–Fisher curve, and the ground state is spin-singlet. The V(d2)- and Cr(d3)-compounds do not show such transition and the ground states are long range antiferromagnetic ordered states. The TMAX, where a short-range magnetic correlation within the chain is fully developed, decreases with increasing the M–M distance within the chain in the compounds with a fixed dn. On the other hand, it decreases with increasing the number of d-electron in the Na-based compounds, although the M–M distance within the chain becomes shorter with increasing the number of d-electron. Any other factor such as the second nearest interaction or orbital degree of freedom should be taken into the consideration for the explanation of the TMAX variation with the number of d-electron. [Copyright &y& Elsevier]

Pulsed NMR measurements have been performed on 3He films adsorbed on an exfoliated graphite sample of area 2 m2. The spectrometer is constructed using a DC SQUID amplifier, with additional positive feedback, and bandwidth 3.4 MHz. The input circuit is a superconducting flux transformer and so is intrinsically broadband. The static magnetic field is provided by a superconducting solenoid enclosed in a niobium shield. We report measurements at the “ferromagnetic anomaly” at frequencies below 50 kHz. A narrow 13C line is also observed, which can be used to directly measure the temperature of the substrate. [Copyright &y& Elsevier]

Abstract: The community focused on collective electronic properties of organic and metal-organic molecular crystals sometimes assumes that these are uniquely a consequence of the fact that the lattice is composed of molecular building blocks. However, quantum mechanics has a wider horizon and precursors for some of the phenomena currently occupying our field were observed and investigated a while ago in various inorganic lattices. We recall some of the latter, which serve to highlight what really is unique to the molecular solid state. We also recall a simplified classification scheme to correlate crystal structures and physical properties. Examples from magnetism include one- and two-dimensional ferromagnetism and complex magnetic lattice topologies; from electron transport we mention low-dimensional superconductors incorporating localized magnetic moments [Copyright &y& Elsevier]

Abstract: Low-dimensional transition metal oxides provide excellent model systems to study magnetic properties induced by the interplay between low-dimensionality character and frustration. In this work, we study polycrystalline Sr3NiIrO6 and Ca3CoIrO6 compounds which exhibit at low temperatures a frozen state with notable dynamic effects that can be attributed to the low-dimensionality character. These dynamic effects are probed by AC susceptibility measurements. [Copyright &y& Elsevier]