Tuning the Magnetic Properties of Cr₂TiC₂T_x through Surface Terminations: A Theoretical Study

Abstract

Recently, magnetic two-dimensional Cr2TiC2Tx MXenes with promising applications in spin electronics have been experimentally confirmed. However, the underlying magnetic mechanism needs to be further investigated. Along these lines, in this work, the magnetic properties of Cr2TiC2On/4F2−n/4 and Cr2TiC2On/4 structures were simulated through first-principle calculations using the GGA+U approach. The values of 4.1 and 3.1 eV were calculated for the Hubbard U of Cr and Ti, respectively, by applying the linear response method. Interestingly, the Cr2TiC2On/4F2−n/4-based configurations with low O content (n ≤ 4) exhibit antiferromagnetic behavior, while the majority of the respective configurations with high O content (n ≥ 5) are ferromagnetic. As far as the Cr2TiC2O5/4F3/4 structure (n = 5) is concerned, the value of about 2.64 μB was estimated for the magnetic moment of the Cr atom. On top of that, the Curie temperature lies within the range of 10~47 K. The extracted theoretical results are in good agreement with experimental outcomes of the Cr2TiC2O1.3F0.8-based structure. From the simulated results, it can be also argued that the magnetic moment of Cr atoms and the Neel temperature can be directly tuned by the active content of O atoms. The conductivity of both Cr2TiC2On/4F2−n/4 and Cr2TiC2On/4 configurations can be regulated by the externally applied magnetic field, while the density of states around the Fermi level shifted significantly between ferromagnetic and antiferromagnetic arrangements. The acquired results provide important theoretical insights to tuning the magnetic properties of Cr2TiC2Tx-based structures through surface termination mechanisms, which are quite significant for their potential applications in spin electronics.

Keywords

• density functional theory
• two-dimensional magnetic materials
• MXene
• spin device
• surface termination