Size-Dependent Critical Temperature and Anomalous Optical Dispersion in Ferromagnetic CrI₃ Nanotubes.

Using first principles calculations, we explored the magnetic and optical properties of chromium(III) iodide (CrI₃) nanotubes (NTs) by changing their chirality and diameter. Here, we considered six types of NTs: (5,0), (5,5), (7,0), (10,0), (10,10), and (12,0) NTs. We found that both zigzag and armchair NTs had a ferromagnetic ground with a direct band gap, although the band gap was dependent on the chirality and diameter.

A 2D ferromagnetic semiconductor in monolayer Cr-trihalide and its Janus structures.

Using first principles calculations, we explored the physical properties of two-dimensional (2D) Cr-trihalide X3-Cr2-X3 or CrX3 (X = Cl, Br, I) and its Janus monolayers X3-Cr2-Y3 (X and Y = Cl, Br, I) where X ≠ Y. We found that Janus monolayer X3-Cr2-Y3 materials are dynamically stable and that it is feasible to synthesize X3-M2-Y3 2D-crystals. Both pristine and Janus layers have intrinsic two-dimensional ferromagnetic semiconducting band structures; the largest band gap of 2.

Hydrogen functionalization induced two-dimensional ferromagnetic semiconductor in Mn di-halide systems.

We explored the electronic and magnetic properties of two-dimensional manganese di-halides (MnY, Y = I, Br, Cl) and hydrogenated systems (MnHY). The pristine MnY monolayers had a very weak magnetic exchange interaction and we found degenerated magnetic states between ferromagnetic and antiferromagnetic states although the Mn had a high magnetic moment of 5 μ with a finite band gap. However, we found that the electronic band structure and magnetic properties could be significantly altered by functionalization with hydrogen atoms because the degeneracy in the pristine MnY structure was broken and the FM ground state was obtained in all MnHY systems.

Graphene flakes obtained by local electro-exfoliation of graphite with a STM tip.

Graphite surfaces can be manipulated by several methods to create graphene structures of different shapes and sizes. Scanning tunneling microscopy (STM) can be used to create these structures either through mechanical contact between the tip and the surface or through electro-exfoliation. In the latter, the mechanisms involved in the process of exfoliation at an applied voltage are not fully understood.

Atomic-scale control of graphene magnetism by using hydrogen atoms.

Isolated hydrogen atoms absorbed on graphene are predicted to induce magnetic moments. Here we demonstrate that the adsorption of a single hydrogen atom on graphene induces a magnetic moment characterized by a ~20-millielectron volt spin-split state at the Fermi energy. Our scanning tunneling microscopy (STM) experiments, complemented by first-principles calculations, show that such a spin-polarized state is essentially localized on the carbon sublattice opposite to the one where the hydrogen atom is chemisorbed.

Stability, adsorption, and diffusion of CH₄, CO₂, and H₂ in clathrate hydrates.

We present a study of the adsorption and diffusion of CH₄, CO₂, and H₂ molecules in clathrate hydrates using ab initio van der Waals density functional formalism [M. Dion, Phys. Rev.