Materializing rival ground states in the barlowite family of kagome magnets: quantum spin liquid, spin ordered, and valence bond crystal states.

The spin- kagome antiferromagnet is considered an ideal host for a quantum spin liquid (QSL) ground state. We find that when the bonds of the kagome lattice are modulated with a periodic pattern, new quantum ground states emerge. Newly synthesized crystalline barlowite (Cu(OH)FBr) and Zn-substituted barlowite demonstrate the delicate interplay between singlet states and spin order on the spin- kagome lattice.

Anomalous thickness-dependent electrical conductivity in van der Waals layered transition metal halide, NbCl.

Understanding the electronic transport properties of layered, van der Waals transition metal halides (TMHs) and chalcogenides is a highly active research topic today. Of particular interest is the evolution of those properties with changing thickness as the 2D limit is approached. Here, we present the electrical conductivity of exfoliated single crystals of the TMH, cluster magnet, NbCl, over a wide range of thicknesses both with and without hexagonal boron nitride (hBN) encapsulation.

Site-Specific Structure at Multiple Length Scales in Kagome Quantum Spin Liquid Candidates.

Realizing a quantum spin liquid (QSL) ground state in a real material is a leading issue in condensed matter physics research. In this pursuit, it is crucial to fully characterize the structure and influence of defects, as these can significantly affect the fragile QSL physics. Here, we perform a variety of cutting-edge synchrotron X-ray scattering and spectroscopy techniques, and we advance new methodologies for site-specific diffraction and L-edge Zn absorption spectroscopy.

NiMoO: Complex antiferromagnetic order on a honeycomb lattice.

Theoretical studies have predicted the existence of topological magnons in honeycomb compounds with stripy or zigzag antiferromagnetic (AFM) order. Here we report the discovery of AFM order in the layered and noncentrosymmetric honeycomb nickelate NiMoO through a combination of magnetization, specific heat, x-ray and neutron diffraction, and electron paramagnetic resonance measurements. The AFM order is complex, with a mixture of stripy and zigzag character on an integer spin noncentrosymmetric honeycomb lattice (6 ).

Scaling and data collapse from local moments in frustrated disordered quantum spin systems.

Recently measurements on various spin-1/2 quantum magnets such as HLiIrO, LiZnMoO, ZnCu(OH)Cl and 1T-TaS-all described by magnetic frustration and quenched disorder but with no other common relation-nevertheless showed apparently universal scaling features at low temperature. In particular the heat capacity C[H, T] in temperature T and magnetic field H exhibits T/H data collapse reminiscent of scaling near a critical point. Here we propose a theory for this scaling collapse based on an emergent random-singlet regime extended to include spin-orbit coupling and antisymmetric Dzyaloshinskii-Moriya (DM) interactions.

Image registration of low signal-to-noise cryo-STEM data.

Combining multiple fast image acquisitions to mitigate scan noise and drift artifacts has proven essential for picometer precision, quantitative analysis of atomic resolution scanning transmission electron microscopy (STEM) data. For very low signal-to-noise ratio (SNR) image stacks - frequently required for undistorted imaging at liquid nitrogen temperatures - image registration is particularly delicate, and standard approaches may either fail, or produce subtly specious reconstructed lattice images. We present an approach which effectively registers and averages image stacks which are challenging due to their low-SNR and propensity for unit cell misalignments.

Observation of Vacancies, Faults, and Superstructures in LnMoO (Ln = La, Y, and Lu) Compounds with Direct Mo-Mo Bonding.

Among oxide compounds with direct metal-metal bonding, the YMoO (ABO) structural family of compounds has a particularly intriguing low-dimensional structure due to the presence of bioctahedral BO dimers arranged in one-dimensional edge-sharing chains along the direction of the metal-metal bonds. Furthermore, these compounds can have a local magnetic moment due to the noninteger oxidation state (+4.5) of the transition metal, in contrast to the conspicuous lack of a local moment that is commonly observed when oxide compounds with direct metal-metal bonding have integer oxidation states resulting from the lifting of orbital degeneracy typically induced by the metal-metal bonding.

Photoinitiated Reactivity of a Thiolate-Ligated, Spin-Crossover Nonheme {FeNO}(7) Complex with Dioxygen.

The nonheme iron complex, [Fe(NO)(N3PyS)]BF4, is a rare example of an {FeNO}(7) species that exhibits spin-crossover behavior. The comparison of X-ray crystallographic studies at low and high temperatures and variable-temperature magnetic susceptibility measurements show that a low-spin S = 1/2 ground state is populated at 0-150 K, while both low-spin S = 1/2 and high-spin S = 3/2 states are populated at T > 150 K. These results explain the observation of two N-O vibrational modes at 1737 and 1649 cm(-1) in CD3CN for [Fe(NO)(N3PyS)]BF4 at room temperature.

Heterometallic Ln/Hg tellurido clusters.

"Ln(TePh)(3)" (Ln = Er, Tm, Lu), prepared in situ by the reduction of PhTeTePh with elemental Ln in the presence of Hg catalyst, reacts with elemental Te to give heterometallic clusters with the formula (py)(7)Ln(3)HgTe(4)(TePh)(3). Structural characterization of all three isostructural derivatives reveals a cubane arrangement of metal ions, with a distorted tetrahedral Hg(II) ion coordinated to three mu(3) coordinate Te(2-) and a terminal TePh ligand. There are two chemically inequivalent types of octahedral Ln(III) ions, one bound to three Te(2-) and three pyridine donors, and two that coordinate two pyridine, three Te(2-), and a terminal TePh ligand.