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The recent emergence of magnetic van der Waals materials allows for the investigation of current-induced magnetisation manipulation in two-dimensional materials. Uniquely, Fe3GeTe2 has a crystalline structure that allows for the presence of bulk spin–orbit torques (SOTs) that we quantify in a Fe3GeTe2 flake. From the symmetry of the measured torques, we identify current induced effective fields using harmonic analysis and find dominant bulk SOTs arising from the symmetry in the crystal structure. Our results show that Fe3GeTe2 can exhibit bulk SOTs in addition to the conventional interfacial SOTs enabling magnetisation manipulation even in thick flakes without the need for complex multilayer engineering. Spin–orbit torques which demonstrates efficient magnetisation switching requires multilayer structures. In FeGe3Te2 van der Waals materials we demonstrate bulk spin–orbit torques in a sole material with possibilities for spintronics applications. [ABSTRACT FROM AUTHOR]

The role of the crystal lattice, temperature and magnetic field for the spin structure formation in the 2D van der Waals magnet Fe5GeTe2 with magnetic ordering up to room temperature is a key open question. Using Lorentz transmission electron microscopy, we experimentally observe topological spin structures up to room temperature in the metastable pre-cooling and stable post-cooling phase of Fe5GeTe2. Over wide temperature and field ranges, skyrmionic magnetic bubbles form without preferred chirality, which is indicative of centrosymmetry. These skyrmions can be observed even in the absence of external fields. To understand the complex magnetic order in Fe5GeTe2, we compare macroscopic magnetometry characterization results with microscopic density functional theory and spin-model calculations. Our results show that even up to room temperature, topological spin structures can be stabilized in centrosymmetric van der Waals magnets. Magnetic skyrmionic bubbles have been reported for Fe5GeTe2 and other layered van der Waals materials and are good candidates for applications in spintronics. Here, the authors report a near room temperature skyrmionic structure for Fe5GeTe2 and study the magnetic ordering for pre and post-cooling states using a combination of magnetic measurements and DFT calculations. [ABSTRACT FROM AUTHOR]

The development of all-solid-state sodium batteries for scalable energy storage solutions requires fast sodium conducting solid electrolytes. To fast-track their discovery, candidate materials need to be identified that are synthesized from abundant resources via cheap and green synthesis routes. Their ion conducting mechanism has to be understood and adapted to meet the stringent requirements for long-term operation in all-solid-state batteries. Here, structure and properties of the sodium hexathiohypodiphosphate Na4P2S6 obtained by two different synthesis methods are compared: a solid-state reaction and a precipitation route from aqueous solution. Combined investigations using powder X-ray diffraction (PXRD), precession electron diffraction (PED), differential scanning calorimetry (DSC), solid-state nuclear magnetic resonance spectroscopy (ssNMR), and Raman spectroscopy reveal that the solid-state synthesized material is characterized by a Na+ and vacancy disorder-driven enantiotropic phase transition at 160 °C (α- to β-Na4P2S6), which is accompanied by a symmetry change of the P2S64− anion. Precipitated Na4P2S6 already crystallizes in a β-like polymorph at room temperature, likely assisted by inter- and intralayer defects. Bond-valence and nudged elastic band (NEB) calculations were employed to identify a low energy, 2D conduction network in β-Na4P2S6, suggesting facile 2D long-range Na+ diffusion. Electrochemical impedance spectroscopy reveals a higher ionic conductivity at room temperature in precipitated β-like Na4P2S6 (2 × 10−6 S cm−1) compared to the solid-state α polymorph (7 × 10−7 S cm−1). The activation energy is around 0.4 eV for both materials. The findings highlight that even subtle structural changes can significantly impact the sodium-ion diffusion in solid electrolytes and at the same time reveal an intricate interplay between phase formation and synthetic control. [ABSTRACT FROM AUTHOR]

The crystal structures of the lanthanide orthothiophosphates LnPS4 (Ln=lanthanide) have been extensively investigated in the past. Up to now, however, single crystals of two members of this series – TmPS4 and YbPS4 – have not been available. Here, we report a modified synthesis protocol for TmPS4 and YbPS4 yielding single crystals suitable for X-ray diffraction. Both compounds crystallize in the tetragonal space group I41/acd (no. 142) with 16 formula units per unit cell and adopt the SmPS4 parent structure, like most reported lanthanide orthothiophosphates. The structures contain isolated [PS4]3− tetrahedra and two crystallographically independent Ln3+ cations, which form trigonal-dodecahedral [LnS8]13− polyhedra. The lattice parameters for TmPS4 are a = 10.598(2), c = 18.877(4) Å with V = 2120.2(6) Å3, and for YbPS4a = 10.577(2), c = 18.827(4) Å with V = 2106.2(7) Å3. The DFT-calculated electronic band structures indicate semiconducting behavior and reveal indirect band gaps of 2.1–2.2 eV, consistent with the reddish brown color of YbPS4, but underestimating the band gap of pale-yellow TmPS4. The Raman spectra are dominated by [PS4]3− vibrations as confirmed by DFT-calculated phonon spectra. DTA measurements reveal remarkably high thermal stability compared to other known orthothiophosphate compounds. [ABSTRACT FROM AUTHOR]

The crystal structures of the lanthanide orthothiophosphates LnPS4 (Ln=lanthanide) have been extensively investigated in the past. Up to now, however, single crystals of two members of this series – TmPS4 and YbPS4 – have not been available. Here, we report a modified synthesis protocol for TmPS4 and YbPS4 yielding single crystals suitable for X-ray diffraction. Both compounds crystallize in the tetragonal space group I41/acd (no. 142) with 16 formula units per unit cell and adopt the SmPS4 parent structure, like most reported lanthanide orthothiophosphates. The structures contain isolated [PS4]3− tetrahedra and two crystallographically independent Ln3+ cations, which form trigonal-dodecahedral [LnS8]13− polyhedra. The lattice parameters for TmPS4 are a = 10.598(2), c = 18.877(4) Å with V = 2120.2(6) Å3, and for YbPS4a = 10.577(2), c = 18.827(4) Å with V = 2106.2(7) Å3. The DFT-calculated electronic band structures indicate semiconducting behavior and reveal indirect band gaps of 2.1–2.2 eV, consistent with the reddish brown color of YbPS4, but underestimating the band gap of pale-yellow TmPS4. The Raman spectra are dominated by [PS4]3− vibrations as confirmed by DFT-calculated phonon spectra. DTA measurements reveal remarkably high thermal stability compared to other known orthothiophosphate compounds. [ABSTRACT FROM AUTHOR]

Inorganic solid‐state synthesis with phosphorus and tellurium requires a careful control of the reaction parameters because of the high volatility of the components. This initial disadvantage can be used as a benefit for the investigation of phase‐formation mechanisms by analyzing the individual vapor pressure behavior. The high‐temperature gas balance is introduced as a device for detection of heterogeneous solid‐gas equilibria in closed reaction systems. The experimentally challenging synthesis of the phosphide telluride Zr2PTe2 is examined as a model system: optimized synthesis runs at lower temperatures (ϑ = 650 °C) in a faster time, while the quantity as well as the crystalline powder quality is increased. A stepwise solid‐solid reaction of zirconium and tellurium according to Ostwald's rule of stages and the shrinking core model is revealed while phosphorus sublimes and subsequently condenses to react to the ternary compound. Additional phenomena such as melting, expansion, and mechanical instabilities can be observed that broaden the possibilities of the gas balance. [ABSTRACT FROM AUTHOR]

Inorganic solid‐state synthesis with phosphorus and tellurium requires a careful control of the reaction parameters because of the high volatility of the components. This initial disadvantage can be used as a benefit for the investigation of phase‐formation mechanisms by analyzing the individual vapor pressure behavior. The high‐temperature gas balance is introduced as a device for detection of heterogeneous solid‐gas equilibria in closed reaction systems. The experimentally challenging synthesis of the phosphide telluride Zr2PTe2 is examined as a model system: optimized synthesis runs at lower temperatures (ϑ = 650 °C) in a faster time, while the quantity as well as the crystalline powder quality is increased. A stepwise solid‐solid reaction of zirconium and tellurium according to Ostwald's rule of stages and the shrinking core model is revealed while phosphorus sublimes and subsequently condenses to react to the ternary compound. Additional phenomena such as melting, expansion, and mechanical instabilities can be observed that broaden the possibilities of the gas balance. [ABSTRACT FROM AUTHOR]

We present the chemical synthesis, crystal-structure determination, and magnetic properties of the quaternary iron nitrides SnxGe1−xFe3N (0 ＜ x ＜ 1). The ternary end members of this series differ in structure, composition, and stability, but both belong to the first spin glasses of iron nitrides. To explore the properties of the quaternary series, a previously established two-step ammonolytic reaction was used to synthesise the compounds. The entire SnxGe1−xFe3N series adopts the antiperovskite structure in space group Pm3̅m with a fully occupied nitrogen position and a Vegard-type increase of the lattice parameter over the compositional range. AC and DC magnetic measurements identify the nitrides of all compositions as canonical spin glasses with a linear increase of Tg from 4 K for Ge-rich to 9 K for Sn-rich nitrides. The competing magnetic orders were confirmed by DFT calculations. [ABSTRACT FROM AUTHOR]