Quantum anomalous Hall state and Weyl nodal line semimetal state in room-temperature magnetic VTiCF2 monolayer

Abstract

Two-dimensional MXenes exhibit exceptional magnetic and topological properties, making them promising candidates for spintronic devices. Herein, we investigate the electronic and magnetic characteristics of HHH- and HTT-phase bimetallic VTiCF2 monolayers via first-principles calculations. Our results show that the HHH-phase VTiCF2 monolayer is a robust out-of-plane ferromagnetic (FM) half-metal with an ultrahigh Curie temperature (TC) of 1020 K. Incorporating spin–orbit coupling transforms it into a quantum anomalous Hall (QAH) insulator with a 36.59 meV bandgap and Chern number C = 1. In contrast, the HTT-phase is a ferrimagnetic (FIM) nodal-line semimetal with in-plane magnetization and TC = 494 K. Notably, the HHH-phase retains its QAH properties under biaxial strains, while the HTT-phase undergoes FIM-to-FM transition at 3% biaxial tensile strain. These findings expand the functional MXene libraries and provide a candidate for room-temperature spintronic devices.