Regensburg 2019 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 31: Frontiers of Electronic-Structure Theory: Focus on the Interface Challenge IV (joint session O/CPP/DS/TT)
TT 31.9: Talk
Tuesday, April 2, 2019, 16:15–16:30, H9
Calculating critical temperatures for magnetic order in two-dimensional materials — •Daniele Torelli — CAMD, Department of Physics, Technical University of Denmark, 2820 Kgs. Lyngby, Denmark
Recent observation of ferromagnetic out-of-plane order in two-dimensional (2D) CrI3 highlights the importance of a microscopic understanding of magnetic anisotropy (MA) in ground state magnetic systems. Single-ion anisotropy and anisotropic exchange coupling comprise crucial ingredients to escape the Mermin-Wagner theorem which implies that rotational symmetry cannot be spontaneously broken at any finite temperature in 2D and thus prevents magnetic order.
In the present work we investigate the variation of critical temperature in Heisenberg model systems using classical Metropolis Monte Carlo simulations. A fit for square, hexagonal and honeycomb lattices leads to a simple expression for the critical temperatures as a function of MA and exchange coupling constants.
Based on a new developed computational 2D materials database, we predict 2D structures with high critical temperatures and high thermodynamic and dynamic stability for future experimental investigations. As testing system, relevant Heisenberg exchange couplings and MA energies in mono-layer CrI3 are obtained from first principle calculations and energy mapping analysis, yielding to an estimation of Curie temperature in good agreement with experimental results.