Prediction of induced magnetism in 2D Ti2C based MXenes by manipulating the mixed surface functionalization and metal substitution computed by xTB model Hamiltonian of the DFTB method

Abstract

We employed the recently developed density functional tight binding (DFTB) method's Hamiltonian, GFN1-xTB, for modeling the mixed termination in Ti₂C MXenes, namely three types of termination by combining –O and –OH, –O and –F, and –F and –OH. We demonstrated that the approach yields reliable predictions for the electronic and magnetic properties of such MXenes. The first highlighted result is that the mixed surface functionalization in Ti₂CA_xB_y MXenes induces spin polarization with diverse magnetic alignments, including ferromagnetism and two types of antiferromagnetism. We further identified the magnetic alignment for the investigated MXene in terms of the compositions of the terminal groups. Moreover, the effect of the transition metal (Ti) substituted by the Sc atom on the electronic and magnetic properties was also investigated. We found that the studied systems maintain the magnetism and the metallic characteristics. A magnetic transition from antiferromagnetic (AFM) to ferrimagnetic (FiM) ordering was found for ScTi₁₅C₈F₈(OH)₈ and ScTi₁₅C₈F₁₂(OH)₄ compounds. Finally, we proved that incorporating the Sc atom into the lattice of Ti₂CO₂ and the mixed surface termination in Ti₂CA_xB_y is an effective strategy to induce magnetism. Our study may provide a new potential application for designing MXene-based spintronics.