Strain engineering of electronic and magnetic properties of double-transition metal ferromagnetic semiconductor MXenes

Abstract

Strain engineering appears as an effective way to modulate physical and chemical properties of two-dimensional (2D) materials. In contrast to their three-dimensional counterparts, 2D materials can withstand high strain before rapture, which promises unique opportunities to control and tune their electronic, optical, and magnetic properties. Recently predicted Hf2MnC2O2 and Hf2VC2O2 double transition metal ferromagnetic semiconductor MXenes show robust ferromagnetic ground state with high Curie temperature. In this study, we investigated the structural, electronic, and magnetic properties of those 2D materials under the biaxial strain using density functional theory. Both strain free monolayers are indirect bandgap semiconductors. Strain engineering can be exploited to turn semiconductor monolayers into metallic or semi-metallic ones depending on the size and type of the applied strain. For instance, a semiconductor to metal transition occurs at −3% compression and 8% tension in Hf2MnC2O2 and also at −2% compression and 9% tension in Hf2VC2O2. Electron and hole effective masses are able to be tuned significantly. The ferromagnetic phase becomes stronger (weaker) as compared to the anti-ferromagnetic phase of both types of monolayers by applying the biaxial tensile (compressive) strain. Our calculations indicated that the Curie temperature (TC) is highly sensitive to the size and type of strain. TC increases (decreases) with the tensile (compressive) strain. While TC is 444 K at a compressive strain of 4%, it becomes 1577 K at a tensile strain of 8% for Hf2MnC2O2.