Tunable magnetic coupling in Mn-doped monolayer MoS2 under lattice strain.

First-principles calculations are conducted to study the electronic and magnetic states of Mn-doped monolayer MoS2 under lattice strain. Mn-doped MoS2 exhibits half-metallic and ferromagnetic (FM) characteristics in which the majority spin channel exhibits metallic features but there is a bandgap in the minority spin channel. The FM state and the total magnetic moment of 1 µ B are always maintained for the larger supercells of monolayer MoS2 with only one doped Mn, no matter under tensile or compressive strain. Furthermore, the FM state will be enhanced by the tensile strain if two Mo atoms are substituted by Mn atoms in the monolayer MoS2. The magnetic moment increases up to 0.50 µ B per unit cell at a tensile strain of 7%. However, the Mn-doped MoS2 changes to metallic and antiferromagnetic under compressive strain. The spin polarization of Mn 3d orbitals disappears gradually with increasing compressive strain, and the superexchange interaction between Mn atoms increases gradually. The results suggest that the electronic and magnetic properties of Mn-doped monolayer MoS2 can be effectively modulated by strain engineering providing insight into application to electronic and spintronic devices.

Circular torsion induced fan-blade shaped wrinkling in two-dimensional nano-rings.

Molecular dynamics (MD) simulations are conducted to study the deformation behavior and strain distribution in two-dimensional (2D) nano-rings of graphene, single-layer black phosphorus (SLBP) and single-layer MoS2 (SLMoS2) under circular torsion. Interestingly, fan-blade shaped wrinkling is generated, in which the maximum torsion angle (Δθ) and the potential energy change per atom (ΔPe) increase with increasing inner radius but decrease with increasing temperature. As the inner radius is increased, the wave number of wrinkling increases but the wave amplitude decreases. The geometrical characteristics of wrinkling are closely related to the intrinsic elastic modulus (E) and Poisson's ratio (ν). Specifically, the graphene nano-rings possess the largest Δθ and ΔPe but the smallest wave amplitude, while the SLBP nano-rings exhibit the smallest Δθ and ΔPe but the largest wave amplitude. Furthermore, the strongly anisotropic E and ν values of SLBP result in orientation-dependent geometrical characteristics of wrinkles, and fan-blade shaped wrinkling with a strain vortex is induced, which might substantially enhance the pseudomagnetic fields and optical funnel effect for the separation of photon-induced electron-hole pairs, and thus be exploited to improve the photoelectric properties of 2D materials.