2 research outputs found
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 Mn<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>
The
manganese orthophosphate, Mn<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>, is characterized by the rich variety of polymorphous modifications,
α-, β′-, and γ-phases, crystallized in monoclinic <i>P</i>2<sub>1</sub>/<i>c</i> (<i>P</i>2<sub>1</sub>/<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 [MnO<sub>5</sub>] and [MnO<sub>6</sub>] polyhedra strengthened by [PO<sub>4</sub>] tetrahedra. All compounds experience long-range antiferromagnetic
order at Neel temperature <i>T</i><sub>N</sub> = 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-Mn<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> 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