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We systematically investigate the structural, electronic, and magnetic properties of a new pentagonal CoBiS monolayer using first-principles and Monte Carlo simulations. We find that Penta-CoBiS is stable mechanically, dynamically, and thermally and is an antiferromagnetic semiconductor with an indirect band gap of 0.5 eV with HSE functional. In addition, the band-gap increased by applying in-plane biaxial strain. We further show that this monolayer has an in-plane easy axis and possesses large intrinsic Dzyaloshinskii–Moriya interaction because of the broken inversion symmetry, and strong spin–orbit coupling originated from the Bi atoms. Moreover, the Néel temperature is also predicted using Monte Carlo simulations. An out-of-plane magnetic field B is then applied to compensate the in-plane anisotropy. It is found that for B = 1.72 T the spins are fully polarized to the out-of-plane direction. Our results demonstrate that Penta-CoBiS monolayer may find numerous applications in flexible spintronics and electronics.

We study in this paper magnetic properties of a system of quantum Heisenberg spins interacting with each other via a ferromagnetic exchange interaction J and an in-plane Dzyaloshinskii-Moriya interaction D. The non-collinear ground state due to the competition between J and D is determined. We employ a self-consistent Green'function theory to calculate the spin-wave spectrum and the layer magnetizations at finite T in two and three dimensions as well as in a thin film with surface effects. Analytical details and the validity of the method are shown and discussed. Numerical solutions are shown for realistic physical interaction parameters. Discussion on possible experimental verifications is given.

We study a crystal of skyrmions generated on a square lattice using a ferromagnetic exchange interaction and a Dzyaloshinskii-Moriya interaction between nearest-neighbors under an external magnetic field. The skyrmion crystal has a hexagonal structure which is shown to be stable up to a temperature Tc where a transition to the paramagnetic phase occur. We will show that the dynamics of the skyrmions at T < Tc follows a stretched exponential law.

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Skyrmions are topologically stable and energetically balanced spin configurations appearing under the presence of ferromagnetic interaction (FMI) and Dzyaloshinskii-Moriya interaction (DMI).Much of the current interest has focused on the effects of magneto-elastic coupling (MEC) on these interactions under mechanical stimuli, such as uniaxial stresses for future applications in spintronics devices. Recent studies suggest that skyrmion shape deformations in thin films are attributed to an anisotropy in the coefficient of DMI, such that D x = D y . This anisotropy is naturally understood as an effect of MEC, however, the relationship between MEC and anisotropy in DMI remains to be clarified. In this paper, we study this problem using a new modeling technique constructed based on Finsler geometry (FG). In the FG model, an MEC is implemented purely geometrically, and the implemented MEC dynamically deforms the coefficients of FMI and DMI to be direction-dependent. This modeling technique is in sharp contrast to the standard model of MEC, in which anisotropic constants are explicitly assumed as an input parameter. Two possible FG models are examined: In the first (second) model, the FG modeling prescription is applied to the FMI (DMI) Hamiltonian. We find that these two different FG models' results are consistent with the reported experimental data for skyrmion deformation. We also study responses of spins under lattice deformations corresponding to uniaxial extension/compression and find a clear difference between these two models in the stripe phase, elucidating which interaction of FMI and DMI is deformed to be anisotropic by uniaxial stresses.

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