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The compound Ni4V3O10 forms a new structure type in the tetragonal space group P4/n. The material can be produced using solid-state synthesis in a narrow temperature range, and the structure was confirmed using X-ray and neutron powder diffraction data. The phase contains occupationally disordered Ni/V in tetrahedral, square pyramidal, and octahedral sites. Bond valence and neutron/X-ray co-refinements give evidence for three vanadium oxidation states (V^3+, V^4+, V^5+), making it distinct in the Ni-V-O system and placing it in a class of only nine other oxides with transition metals exhibiting three oxidation states. With a Néel temperature of 38 K and a Curie-Weiss parameter θ = -234 K, it displays frustrated antiferromagnetism, evidenced by a broad hump in the heat capacity below T_N. The structure has a percolating distorted rock-salt-like network, leading to strong superexchange, but square pyramidal linkages frustrate magnetic ordering. The magnetic structure is assumed to be incommensurate, as simple propagation vectors can be ruled out by powder neutron diffraction.

The grand challenge of synthesizing materials by predictive design remains outstanding because controlling all necessary thermodynamic and kinetic factors quickly becomes intractable, even for well...

The compound (ethylenediamine-N)-bis(ethylenediamine-N,N′)-copper(II) bis(nitrate) is reported. It has an asymmetric unit containing Cu(II) penta-coordinating to two chelating ethylenediamine (en) and one monodentate en ligands with square-pyramidal-based geometry having severe trigonal distortion, together with two nitrate anions. It is the first crystallographic confirmation of the existence of penta-coordination with exclusively en ligands for any metal center, as well as the first monodentate en attached to Cu(II) seen in the solid state. It can be visualized as the penta-ammine effect realized solely with bi-amine ligands, defying the presumed necessity of mono-amines. X-ray crystallography establishes it to have P21/c space group with a = 12.83 A, b = 9.77 A, c = 11.91 A, and β = 94.8° (at 100 K). Spectroscopic analysis of this compound is consistent with the crystallographic assessment of the coordination chemistry, and it is found to be a S = 1/2 paramagnet.

We report the magnetic phase diagram of ${\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}{\mathrm{PSe}}_{3}$, which represents a random magnet system of two antiferromagnetic systems with mixed spin, mixed spin anisotropies, mixed nearest-neighbor magnetic interactions, and mixed periodicities in their respective antiferromagnetic structure. Bulk samples of ${\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}{\mathrm{PSe}}_{3}$ have been prepared and characterized phase pure by powder x-ray and neutron diffraction and x-ray fluorescence. Nature and extent of magnetically ordered state has been established using powder neutron diffraction, dc magnetic susceptibility, and heat capacity. Long-range magnetic ordering exists between $x=0.0$ and 0.25 (${\mathrm{MnPSe}}_{3}$ type) and between $x=0.875$ and 1 (${\mathrm{FePSe}}_{3}$ type). A short-range magnetic order with the existence of both ${\mathrm{MnPSe}}_{3}$- and ${\mathrm{FePSe}}_{3}$-type nanoclusters has been established between $x=0.25$ and 0.875. Irreversibility in dc magnetization measurements, also characterized by isothermal and thermoremanent magnetization measurements, suggest similarities to magnetic nanoparticles where uncompensated surface spins result in diverging thermoremanent and isothermal remanent magnetization responses, further reinforcing existence of magnetic nanoclusters or domains. A spin-glass state, observed in analogous ${\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}{\mathrm{PS}}_{3}$, has been ruled out, and formation of nanoclusters exhibiting both ordering types results from unusually high anisotropy values. The effect of ligand contributions to the spin-orbit interactions has been suggested as a possible explanation for high $D$ values in these compounds.

Semiconducting binary sulfides are often produced with controlled size and shape by solvothermal synthesis using amine solvents. The versatility of this method, however, has not been extended to dense ternary sulfides that include alkali and transition metal ions, which are renowned for their complex magnetic and electronic properties. We report the solvothermal synthesis of the alkali–transition metal sulfides KFeS2 and KFe2S3. The latter compound is not accessible by direct solid-state synthesis. Magnetic susceptibility measurements indicate antiferromagnetic ordering of KFeS2 and KFe2S3, which contain single and double chains of FeS4 tetrahedra, respectively. Given the ability to access KFe2S3 here, further development of this method may lead to isolation of new functional compounds.

Rapid materials discovery in inorganic chemistry should combine predictive computational tools with fast experimental syntheses. We apply such a tandem approach to explore the Ba–Ru–S phase space, where no ternary compounds are yet known to exist. Related ternary oxide ruthenates and ternary iron sulfides exhibit interesting electronic properties due to d-electron correlations, such as superconductivity, metamagnetism, and quantum phase transitions. We use a combination of evolutionary algorithms and density functional theory to inform traditional and in situ diffraction methods. In the course of our investigation, we find that convex hull constructions of the binary constituents inform interpretation of the ternary hull, which in this case has two compounds near thermodynamic stability. Our experimental study does not reveal formation of the candidates BaRu2S2 or BaRuS3, but it does provide the structure of a high-temperature polymorph of BaS2. This methodology can be exploited to study other ternary sys...

We report a detailed investigation of ${\mathrm{K}}_{2}{\mathrm{MnS}}_{2}$ and ${\mathrm{K}}_{2}{\mathrm{MnSe}}_{2}$ from the ${\mathrm{K}}_{2}{\mathrm{MnS}}_{2}$ structure type and their magnetic solid solution ${\mathrm{K}}_{2}{\mathrm{MnS}}_{2\ensuremath{-}x}{\mathrm{Se}}_{x}$ and find that compounds of this structure type consist of strongly coupled pseudo-one-dimensional antiferromagnetic chains that collectively represent a frustrated two-dimensional triangular antiferromagnet. Bulk samples of ${\mathrm{K}}_{2}{\mathrm{MnS}}_{2\ensuremath{-}x}{\mathrm{Se}}_{x}$ with $0\ensuremath{\le}x\ensuremath{\le}2$ are characterized using x-ray diffraction, neutron diffraction, magnetization, and heat-capacity measurements. An incommensurate cycloid magnetic structure with a magnetic propagation vector $k=[0.58\phantom{\rule{0.16em}{0ex}}0\phantom{\rule{0.16em}{0ex}}1]$ is observed for all samples in ${\mathrm{K}}_{2}{\mathrm{MnS}}_{2\ensuremath{-}x}{\mathrm{Se}}_{x}$, and the ordering is robust despite a 12% increase in cell volume. Geometric frustration of chains results in incommensurability along $a$ and a two-step magnetic transition. The varying geometries accessible in compounds of this structure type are presented as promising avenues to tune frustration.

We report on changes in the thermal conductivity of solid-state synthesized $\mathrm{M}{\mathrm{n}}_{x}M\mathrm{Ge}$ ($M=\mathrm{Co}$, Ni, $0.98lxl1.02$) alloys through their temperature-induced martensitic structural transition. The thermal conductivity is measured by time-domain thermoreflectance. $\mathrm{M}{\mathrm{n}}_{1.014}\mathrm{NiGe}$ exhibits an increase in thermal conductivity from 11 to $15.5\phantom{\rule{0.16em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ from approximately 575 to 625 K, and $\mathrm{M}{\mathrm{n}}_{1.007}\mathrm{CoGe}$ exhibits an increase in thermal conductivity from 7 to $8.5\phantom{\rule{0.16em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ from 500 to 550 K. In $\mathrm{M}{\mathrm{n}}_{x}\mathrm{NiGe}$, the transition temperature and the magnitude of the change in thermal conductivity are strongly dependent on the alloy composition. Our study advances the fundamental understanding of the thermal transport properties in the $\mathrm{M}{\mathrm{n}}_{x}M\mathrm{Ge}(M=\mathrm{Co},\phantom{\rule{0.16em}{0ex}}\mathrm{Ni})$ family of alloys and opens a new direction in the search for solid-state phase transition materials with potential applications as thermal regulators.

In permanent magnet applications, response often scales with volume or dimension in power-conversion and magnetostrictive applications, even in film form. In microelectromechanical devices it is necessary to explore versatile methods of dense film deposition with film thicknesses approaching one micron. In this study, we present a wet chemical route to hard magnetic cobalt ferrite (CoFe2O4) films to produce films with large coercivity, controllable thickness, saturation approaching that of the bulk, and smoother morphology than state-of-the art sputtered or pulsed-laser-deposited films. The development of etching and releasing processes demonstrates how these films are suitable for precise engineering in a variety of form factors and applications.

Expanding the library of known inorganic materials with functional electronic or magnetic behavior is a long-standing goal in condensed matter physics and materials science. Recently, the transition metal chalcogenides including selenium and sulfur have been of interest because of their correlated-electron properties, as seen in the iron-based superconductors and the transition metal dichalcogenides. However, the chalcogenide chemical space is less explored than that of oxides, and there is an open question of whether there may be new materials heretofore undiscovered. We perform a systematic combined theoretical and experimental search over ternary phase diagrams that are empty in the Inorganic Crystal Structure Database containing cations, transition metals, and one of selenium or sulfur. In these 27 ternary systems, we use a probabilistic model to reduce the likelihood of false negative predictions, which results in a list of 24 candidate materials. We then conduct a variety of synthesis experiments to check the candidate materials for stability. While the prediction method did obtain previously unknown compositions that are predicted stable within density functional theory, none of the candidate materials formed in our experiments. We come to the conclusion that these phase diagrams are ``empty'' in the case of bulk synthesis, but it remains a possibility that alternate synthesis routes may produce some of these phases.