Magnetic materials with noncollinear spin arrangements are of considerable interest owing to their potential use in emerging computational technologies and memory devices. Competing magnetic interactions, i.e., magnetic frustration, are one of the main origins of noncollinear magnetic structures. While frustrated systems have been mainly studied among magnetic insulators, combining magnetic frustration with electrical conductivity can allow simultaneous charge and spin manipulation, which is crucial for the design of electronic devices. Here, we present a new intermetallic solid solution LaMn_2–xAu_4+x, whose crystal structure accommodates magnetically frustrated Mn square nets. Powder neutron diffraction and first-principles analysis provide evidence that the metallic LaMn_2–xAu_4+x phase can host the frustration-driven hedgehog spin-vortex crystal─a rare noncollinear magnetic state, which was previously exclusively observed for iron pnictides. 

Light-emitting materials based on earth-abundant metals, such as manganese hold great promise as emitters for organic lighting devices. In order to apply such emitter materials and, in particular, to overcome the problem of self-quenching due to cross-relaxation, we investigated a series of tetrabromidomanganate ([MnBr₄]²⁻) salts with bulky tetraalkylphosphonium counter cations [P_nnn]⁺, namely [P_nnnn]₂[MnBr₄] (n = 4 (1), 6 (2) and 8 (3)), which can be obtained by a straightforward reaction of the respective phosphonium bromide and MnBr₂. Variation of the cation size allows control of the properties of the resulting ionic materials. 1 and 3 qualify as ionic liquids (ILs), where 1 features a melting point of 68 °C, and 3 is liquid at room temperature and even at very low temperatures. Furthermore, 1 and 2 show the formation of higher-ordered thermotropic mesophases. For 1 a transition to a thermodynamically metastable smectic liquid crystalline phase can be observed at room temperature upon reheating from the metastable glassy state; 2 appears to form a plastic crystalline phase at ∼63 °C, which persists up to the melting point of 235 °C. The photoemission is greatly affected by phase behaviour and ion dynamics. A photoluminescence quantum yield of 61% could be achieved, by balancing the increase in Mn²⁺-Mn²⁺ separation and reducing self-quenching through increasingly large organic cations which leads to adverse increased vibrational quenching. Compared to analogous ammonium compounds, which have been promoted as @#x0308;inorganic hybrid perovskite, the phosphonium salts show superior performance, with respect to photoluminescent quantum yield and thermal and air/humidity stability. As the presented compounds are not sensitive to the atmosphere, in particular moisture, and show strong visible electroluminescence in the green region of light, they are important emitter materials for use in organic light-emitting devices.

Reaction of the elements yielded Ca₃Pt₄Bi₈ and CaPtBi, which are, to the best of our knowledge, the first reported ternary Ca–Pt–Bi compounds. The compounds crystallize isostructural to the Pd analogs Ca₃Pd₄Bi₈ (own structure type) and CaPdBi (TiNiSi structure type), respectively. Employing a multistep temperature treatment allows for the growth of mm-sized single crystals of Ca₃Pd₄Bi₈ and Ca₃Pt₄Bi₈ from a Bi self-flux. Their crystal structures can be visualized as consisting of a three-dimensional extended polyanion [M₄Bi₈]^6– (M = Pd, Pt), composed of interlinked M–Bi chains propagating along the c direction, and Ca²⁺ cations residing in one-dimensional channels between the chains. First-principles calculations reveal quasi-one-dimensional electronic behavior with reduced effective electron masses along [001]. Bader analysis points to a strong anionic character of the M species (M = Pd, Pt) in Ca₃M₄Bi₈. Thus, it is more appropriate to address the compounds Ca₃Pd₄Bi₈ and Ca₃Pt₄Bi₈ as a palladide and platinide, respectively. Magnetization measurements indicate diamagnetic behavior with no indications for superconductivity down to 2 K. Electrical resistivity data are consistent with metallic behavior and suggest predominant electron–phonon scattering.

By employing the pyridinium hexafluorophosphate task-specific ionic liquids 1-butyl-4-methylpyridinium hexafluorophosphate ([C₄mpyr][PF₆]) and 1-ethylpyridinium hexafluorophosphate ([C₂pyr][PF₆]) as the reaction medium, mineralizer, structure-directing agent, and, in the case of the smaller pyridinium cation, even a structural component, it was possible to obtain five new alkali metal iron phosphates featuring interconnected FeX₆ octahedra and PX₄ (X = F, O, or OH) tetrahedra. NaFe(PO₃F)₂ (1) is a dense 3D structure, RbFe(PO₃F)(PO₂(OH)F)(PO₂(OH)₂) (2) features 1D strands, (C₂pyr)LiFe(PO₃F)₃(PO₂F₂)F (3) has 2D layers, and LiFe(PO₃F)(PO₂F₂)F (4) as well as Cs_0.75Fe(PO_2.75(OH)_0.25F)(PO₂F₂)₂ (5) are 3D open frameworks. While in 1–2 as well as in 4 and 5, FeX₆ octahedra and PX₄ (X = F, O, or OH) tetrahedra alternate, 3 features octahedra dimers, Fe₂X₁₁ (X = F, O, or OH). The magnetic behavior of all compounds is governed by antiferromagnetic interactions. Interestingly, 3 exhibits a broad maximum in the temperature dependence of the magnetic susceptibility, characteristic of a low-dimensional magnetic system consistent with the presence of Fe–Fe dimers in its crystal structure. 

A new family of oxofluorophoshates, AFe(PO₃F)₂ (A = K, (NH₄)₂Cl, NH₄, Rb, and Cs), was synthesized via ionothermal methods using PF₆ ionic liquids. Single-crystal and powder X-ray diffraction reveal that AFe(PO₃F)₂ with A = (NH₄)₂Cl crystallizes in a trigonal structure, while AFe(PO₃F)₂ with A = NH₄, Rb, and Cs crystallizes in a triclinic structure. Dimorphic KFe(PO₃F)₂ crystallizes in both the trigonal and triclinic forms. The structures of all compounds feature Yavapaiite-like Fe(PO₃F)₂ slabs, which are characterized by triangular Fe layers, planar in the case of the trigonal structure and undulated in the case of the triclinic one. Magnetization measurements reveal all compounds to order antiferromagnetically at low temperatures. The trigonal phases AFe(PO₃F)₂ (A = K and (NH₄)₂Cl) display complex magnetic H–T phase diagrams. The observation of magnetization plateaus at M_sat/3 (M_sat = saturation magnetization) indicates the existence of the up–up–down (UUD) and V-phases at applied magnetic fields in the magnetically ordered state. Powder neutron diffraction measurements of KFe(PO₃F)₂ confirm the 120° spin structure at zero fields. Along c, the magnetic moments form a commensurate spiral since the spins in each plane are rotated by 90° with respect to the adjacent one. To our knowledge, this is the first time such a non-centrosymmetric version of the 120° spin structure with a 90° rotation between nearest planes has been reported.

Large black single crystals with a metallic luster of Li₁₆Sr₆Ge₆N and several other representatives of the series Li₁₆Ae₆Tt₆N and Li₁₆Ae₆Tt_6.5 (Ae=Ca, Sr; Tt=Si, Ge, Sn, Pb) were grown from mixtures of the respective elements with addition of binary alkaline-earth metal nitrides or lithium nitride in the case of the nitrides. For the synthesis a modified high-temperature centrifugation-aided filtration (HTCAF) technique using reactive lithium melts was employed. These metallic phases crystallize in an ordered defect-variant of the Sc₁₁Ir₄ type with selective occupation of the smaller octahedral voids in the origin (000) with N and the larger rhombic dodecahedral voids in (00 1/2 ) with Tt. Charge balance assuming the presence of exclusively closed shell ions for all examples accounts for an electronic excess. Diamagnetism despite metallic properties is consistent with results from electronic structure calculations.

The structural and magnetic properties of the ThCr₂Si₂-type solid solution LaMn₂(Ge_1−xSi_x)₂ (x = 0.0 to 1.0) have been investigated employing a combination of X-ray diffraction, magnetization and neutron diffraction measurements, which allowed establishing a magnetic composition-temperature phase diagram. Substitution of Ge by Si leads to a compression of the unit cell, which affects the magnetic exchange interactions. In particular, the magnetic structure of LaMn₂(Ge_1−xSi_x)₂ is strongly affected by the unit cell parameter c, which is related to the distance between adjacent Mn layers. Commensurate antiferromagnetic layers and a canted ferromagnetic structure dominate the Si-rich part of the solid solution, whilst an incommensurate antiferromagnetic flat spiral and a conical magnetic structure are observed in the Si-poor part.

Germanium clathrates with the type II structure are open-framework materials that show promise for various applications, but the difficulty of achieving phase-pure products via traditional synthesis routes has hindered their development. Herein, we demonstrate the synthesis of type II Ge clathrates in a two-electrode electrochemical cell using Na₄Ge_4–ySi_y (y = 0, 1) Zintl phase precursors as the working electrode, Na metal as the counter/reference electrode, and Na-ion conducting β″-alumina as the solid electrolyte. The galvanostatic oxidation of Na₄Ge₄ resulted in voltage plateaus around 0.34–0.40 V vs Na/Na⁺ with the formation of different products depending on the reaction temperature. When using Na₄Ge₃Si as a precursor, nearly phase-pure, alloyed type II Ge–Si clathrate was obtained at 350 °C. The Na atoms in the large (Ge,Si)₂₈ cages of the clathrate occupied off-centered positions according to Rietveld refinement and density functional theory calculations. The results indicate that electrochemical oxidation of Zintl phase precursors is a promising pathway for synthesizing Ge clathrates with type II structure and that Si alloying of the Zintl phase precursor can promote selective clathrate product formation over other phases. 

A systematic investigation of the ternary system Yb-Mn-Sb led to the discovery of the novel phase Yb10MnSb9. Its crystal structure was characterized by single-crystal X-ray diffraction and found to be complex and highly disordered. The average Yb10MnSb9 structure can be considered to represent a defect modification of the Ca10LiMgSb9 type and to crystallize in the tetragonal P4(2)/mnm space group (No. 136) with four formula units per cell. The structural disorder can be associated with both occupational and positional effects on several Yb and Mn sites. Similar traits were observed for the structure of the recently reported Yb21Mn4Sb18 phase (monoclinic space group C2/c, No. 15), which was reevaluated as part of this study as well. In both structures, distorted Sb-6 octahedra centered by Yb atoms and Sb-4 tetrahedra centered by Mn atoms form disordered fragments, which appear as the hallmark of the structural chemistry in this system. Discussion along the lines of how difficult, and important, it is to distinguish Yb10MnSb9 from the compositionally similar binary Yb11Sb10 and ternary Yb14MnSb11 compounds is also presented. Preliminary transport measurements for polycrystalline Yb10MnSb9 indicate high values of the Seebeck coefficient, approaching 210 mu V K-1 at 600 K, and a semiconducting behavior with a room-temperature resistivity of 114 m Omega cm.

Although compound formation between two elements is well studied, thorough investigations make it possible to uncover new binary compounds. A re-examination of the La-Au system revealed three new phases, which were characterized with respect to their structural and electronic properties as well as thermal stability: La7Au3 (Th7Fe3 type, space group P6(3)mc, Pearson code hP20) appears to be metastable. It can be obtained by slow crystallization from a stoichiometric melt. La3Au2 (U3Si2 type, space group P4/mbm, Pearson code tP10) is stable up to 1013 K, where it decomposes peritectically. La3Au, (Pu3Pd4 type, space group R (3) over bar, Pearson code hR14) is thermally stable up to at least 1273 K. In addition, the crystal structures of La2Au(anti-PbCl2 type, space group Pnma, Pearson code oP12) and alpha-LaAu (FeB type, space group Pnma, Pearson code oP8) could be determined by single-crystal X-ray diffraction. The electronic structures and chemical bonding have been evaluated from first principles calculations. They show that all compounds can be viewed as electron-rich, polar intermetallics.