A Monte Carlo study of two dimensional Ising magnet CrI3.

Abstract

The presence of magnetic order in a layered 2D material is one of the great discoveries. A few years back, the presence of magnetic order in lower dimensional materials (1D or 2D) was not possible according to the Mermin-Wagner theorem, but the presence of a finite gap in the spectrum indicates a magnetic phase transition[22]. This report is a study of the ferromagnetic phase transition in a monolayer of chromium tri-iodide (CrI3). Chapter result-II shows the ferromagnetic phase transition in a monolayer of CrI3. We have started with chapter 1, in which we have described the history, method of production, and experimental detection of magnetism in the monolayer of CrI3 very briefly. After that, in Chapter 2, we discussed the layered ”CrI3” crystal structure, bond length, magnetic moment, etc. In chapter 3, we have studied some of the impor tant magnetic models, mainly the Ising model, because we are working only on the Ising model, followed by the Monte Carlo simulation and algorithm discussed in chapter 4. After that, we applied Monte Carlo simulation to square lattice and honeycomb lattice, and the results are presented in Chapter 5. Chapter 6 discusses some of the magnetic anisotropies that are responsible for the magnetic order in two-dimensional materials, and the final results for the monolayer of CrI3 are presented in Chapter 7. In the next chapter (chapter 8), we will analyse the results in various ways, like how we obtained the variation of specific heat with temperature for different lattice sizes. We have also plotted the variation of specific heat with temperature for different values of anisotropic constants to observe the effect of the anisotropic constant on the results. In the next section, we have presented the results for the monolayer of CrCl3, CrBr3, and CrI3 and a comparison between them to observe the effect of non-magnetic ions on the results. In chapter 9, the ferromagnetic phase transition is explained in great detail. We obtained the best fit (using polynomial fit) for our original magnetization curve. In the last chapter, we have listed all the results, conclusions drawn from the results, and a summary of the entire work.