Pressure-Driven Metallization in Hafnium Diselenide.

The quest for new transition metal dichalcogenides (TMDs) with outstanding electronic properties operating under ambient conditions draws us to investigate the 1T-HfSe polytype under hydrostatic pressure. Diamond anvil cell (DAC) devices coupled to synchrotron X-ray, Raman, and optical (VIS-NIR) absorption experiments along with density functional theory (DFT)-based calculations prove that (i) bulk 1T-HfSe exhibits strong structural and vibrational anisotropies, being the interlayer direction especially sensitive to pressure changes, (ii) the indirect gap of 1T-HfSe tends to vanish by a -0.1 eV/GPa pressure rate, slightly faster than MoS or WS, (iii) the onset of the metallic behavior appears at ∼10 GPa, which is to date the lowest pressure among common TMDs, and finally, (iv) the electronic transition is explained by the bulk modulus - correlation, along with the pressure coefficient of the band gap, in terms of the electronic overlap between chalcogenide p-type and metal d-type orbitals.

High pressure exploration in the Li-Ln-V-O system.

Using in situ high pressure Raman spectroscopy, two structural changes were observed in a sample of the composition LiLa5O5(VO4)2. Taking this into account and by combining different conditions, three new compounds were further obtained from high pressure-high temperature synthesis. Their crystal structure description was done using the antiphase approach, which implies the presence of oxygen-centered [OLn4] building units, where Ln is La for (1) β-LiLa5O5(VO4)2 and (2) β-LiLa2O2(VO4) or Nd for (3) LiNd5O5(VO4)2 compounds.

Characterization and Decomposition of the Natural van der Waals SnSbTe under Compression.

High pressure X-ray diffraction, Raman scattering, and electrical measurements, together with theoretical calculations, which include the analysis of the topological electron density and electronic localization function, evidence the presence of an isostructural phase transition around 2 GPa, a Fermi resonance around 3.5 GPa, and a pressure-induced decomposition of SnSbTe into the high-pressure phases of its parent binary compounds (α-SbTe and SnTe) above 7 GPa. The internal polyhedral compressibility, the behavior of the Raman-active modes, the electrical behavior, and the nature of its different bonds under compression have been discussed and compared with their parent binary compounds and with related ternary materials.

Large Magnetoelectric Coupling Near Room Temperature in Synthetic Melanostibite Mn FeSbO.

Multiferroic materials exhibit two or more ferroic orders and have potential applications as multifunctional materials in the electronics industry. A coupling of ferroelectricity and ferromagnetism is hereby particularly promising. We show that the synthetic melanostibite mineral Mn FeSbO (R3‾ space group) with ilmenite-type structure exhibits cation off-centering that results in alternating modulated displacements, thus allowing antiferroelectricity to occur.

Effect of composition and coating on the interparticle interactions and magnetic hardness of MFeO (M = Fe, Co, Zn) nanoparticles.

Single domain superparamagnetic ferrite nanoparticles with the composition MFeO (M = Fe, Co, Zn) have been prepared by thermal decomposition of metal acetylacetonates in diphenyl ether or dibenzyl ether, using oleic acid in the presence of oleylamine as a stabilizing agent. The Fe, Co and Zn ferrite nanoparticles are monodisperse with diameters of 4.9, 4.