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In this paper, I have tried to analyze the electrical properties and the experimental data related to drain current–drain voltage of the Zn 0.7 Mg 0.3 O / ZnO / Zn 0.7 Mg 0.3 O heterojunction field effect transistor by use of Hoffman nonideal model theoretically. Also by use of different scattering mechanisms in two-dimensional electron gas structures, I have studied the electrical transport properties of this structure and most important effective parameters for controlling electron mobility in the range of 75 to 300 K have been studied theoretically.

Among the numerous 2D system that can be prepared via exfoliation, iron phosphorus trisulfide (FePS3) attracts a lot of attention recently due to its broad-range photoresponse, its unusual Ising-type magnetic order and possible applications in spintronic nano-devices. Despite various experimental and theoretical-computational reports, there are still uncertainties in identifying its magnetic ground state. In this paper, we investigate the structural and magnetic properties of single-layer FePS3 by using Density Functional Theory. Our findings show that orbital ordering leads to a variation in distance between pairs of iron atoms by 0.14 Å. These lattice distortions, albeit small, trigger different (ferromagnetic and antiferromagnetic) exchange couplings so that the ground state consists of ferromagnetically aligned zigzag chains along the long Fe -Fe bonds which couple antiferromagnetically along the shorter Fe -Fe bonds. Within the DFT+U framework, we parameterize a spin Hamiltonian including Heisenberg, single-ion anisotropy, Dzyaloshinskii-Moriya and biquadratic interactions. Using U = 2.22 eV gives a consistent description of both the electronic band gap and the Neel temperature in 2D FePS3.

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In this study, I have investigated the magnetic and critical properties of manganese pyrochlore fluoride NaSrMn2F7, which exhibits a glass transition at Tf = 2.5 (K) due to charge disorder. A DFT + U + SOC framework is used in this paper to derive spin-Hamiltonian terms, including isotropic and anisotropic exchange interactions. An optimized geometry reveals a local distortion of the F–Mn–F angle along the ⟨111⟩ direction (95.48° and 84.51°), which is considered a weak bond disorder (δJ). Despite the complex structure of this material, first principle calculations show that its magnetic properties are only controlled by the nearest neighbor’s Heisenberg exchange interaction, and other interactions do not affect spin arrangements in the ground state. Thus, this material is considered a suitable candidate for studying electron correlation in spin glasses. Using a replica-exchange framework, Monte Carlo simulations indicate that with δJ=0, no phase transition is observed when magnetic susceptibility changes with temperature. The results demonstrate that the presence of local bond disorder serves as a perturbation, and the degeneracy of the energy manifold of the system persists if its effect is not taken into consideration. Based on δJ=0.13(meV) and the derived spin Hamiltonian, 2.6 (K) is obtained as the phase transition temperature.