Adjustment of ferromagnetism and improvement of the electronic structure of the TiI3 monolayer by the substitutional doping of 3d transition metal atoms: Ab-initio investigation

Abstract

Two dimensional Van der Waals materials are very attractive for several researchers because of their distinctive properties and their interesting applications in data storage and spintronic devices. Titanium triiodide (TiI3), which is classified among transition metal trihalides (MX3), has received more attention after CrI3 and VI3 monolayers. Here, we explore the structural, electronic and magnetic properties of pure and 3d TM (TM = Sc, V, Cr, Mn and Fe) doped TiI3 monolayer using first-principles calculations, based on the GGA + Ueff approach. We confirmed the dynamic stability of TiI3 monolayer using phonon calculations and the thermal stability of pure and TM-doped TiI3 monolayers by performing AIMD simulation. We further found that the pure TiI3 monolayer is a stable ferromagnetic semiconductor with intrinsic magnetism. The introduction of vacancy defects in the pristine TiI3 monolayer showed that it is desirable to introduce TM atoms into Ti positions, which led to the improvement of its electronic and magnetic properties. The Sc-doped system keeps its semiconductor behavior with a reduction in the width of the band gap, whereas V-, Cr- and Fe-doped TiI3 monolayers turn into half semiconductors (HSC). Even more impressive, the Mn-doped system is found to be a bipolar ferromagnetic semiconductor (BFMS). We applied spin orbit coupling (SOC) on simulated monolayers, and showed that it affected them by changing their band gaps widths, especially in Fe-doped TiI3 monolayer. Furthermore, we found in all doped systems a ferromagnetic stability, an enhancement of the total magnetic moment, up to 10 μB in Cr- and Fe-doped monolayers, high Curie temperatures, up to 260 K, and high magnetic anisotropic energies, especially in Mn-doped TiI3 monolayer which makes it possess a long range ferromagnetic order. These interesting results concerning the electronic and magnetic properties of pure and transition metals-doped TiI3 monolayers are extremely beneficial for tune and enhance electronic and spintronic devices.