Stable Sulfuric Vapor Transport and Liquid Sulfur Growth on Transition Metal Dichalcogenides

Transition metal dichalcogenides (TMDs) are an emergent class of low-dimensional materials with growing applications in the field of nanoelectronics. However, efficient methods for synthesizing large monocrystals of these systems are still lacking. Here, we describe an efficient synthetic route for a large number of TMDs that were obtained in quartz glass ampoules by sulfuric vapor transport and liquid sulfur. Unlike the sublimation technique, the metal enters the gas phase in the form of molecules, hence containing a greater amount of sulfur than the growing crystal. We have investigated the physical properties for a selection of these crystals and compared them to state-of-the-art findings reported in the literature. The acquired electronic properties features demonstrate the overall high quality of single crystals grown in this work as exemplified by CoS2, ReS2, NbS2, and TaS2. This new approach to synthesize high-quality TMD single crystals can alleviate many material quality concerns and is suitable for emerging electronic devices

Structure–Property Relationships in α‑, β′‑, and γ‑Modifications of Mn₃(PO₄)₂

The manganese orthophosphate, Mn₃(PO₄)₂, is characterized by the rich variety of polymorphous modifications, α-, β′-, and γ-phases, crystallized in monoclinic <i>P</i>2₁/<i>c</i> (<i>P</i>2₁/<i>n</i>) space group type with unit cell volume ratios of 2:6:1. The crystal structures of these phases are constituted by three-dimensional framework of corner- and edge-sharing [MnO₅] and [MnO₆] polyhedra strengthened by [PO₄] tetrahedra. All compounds experience long-range antiferromagnetic order at Neel temperature <i>T</i>_N = 21.9 K (α-phase), 12.3 K (β′-phase), and 13.3 K (γ-phase). Additionally, second magnetic phase transition takes place at <i>T</i>* = 10.3 K in β′-phase. The magnetization curves of α- and β′-modifications evidence spin-floplike features at <i>B</i> = 1.9 and 3.7 T, while the γ-Mn₃(PO₄)₂ stands out for an extended one-third magnetization plateau stabilized in the range of magnetic field <i>B</i> = 7.5–23.5 T. The first-principles calculations define the main paths of superexchange interaction between Mn spins in these polymorphs. The spin model for α-phase is found to be characterized by collection of uniform and alternating chains, which are coupled in all three directions. The strongest magnetic exchange interaction in γ-phase emphasizes the trimer units, which make chains that are in turn weakly coupled to each other. The spin model of β′-phase turns out to be more complex compared to α- or γ-phase. It shows complex chain structures involving exchange interactions between Mn2 (Mn2′, Mn2″) and Mn3 (Mn3′, Mn3″). These chains interact through exchanges involving Mn1 (Mn1′, Mn1″) spins