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Manipulation of electronic and magnetic properties of M2_2C (M=Hf, Nb, Sc, Ta, Ti, V, Zr) monolayer by applying mechanical strains

Abstract

Tuning the electronic and magnetic properties of a material through strain engineering is an effective strategy to enhance the performance of electronic and spintronic devices. Recently synthesized two-dimensional transition metal carbides M2_2C (M=Hf, Nb, Sc, Ta, Ti, V, Zr), known as MXenes, has aroused increasingly attentions in nanoelectronic technology due to their unusual properties. In this paper, first-principles calculations based on density functional theory are carried out to investigate the electronic and magnetic properties of M2_2C subjected to biaxial symmetric mechanical strains. At the strain-free state, all these MXenes exhibit no spontaneous magnetism except for Ti2_2C and Zr2_2C which show a magnetic moment of 1.92 and 1.25 μB\mu_B/unit, respectively. As the tensile strain increases, the magnetic moments of MXenes are greatly enhanced and a transition from nonmagnetism to ferromagnetism is observed for those nonmagnetic MXenes at zero strains. The most distinct transition is found in Hf2_2C, in which the magnetic moment is elevated to 1.5 μB\mu_B/unit at a strain of 15%. We further show that the magnetic properties of Hf2_2C are attributed to the band shift mainly composed of Hf(5dd) states. This strain-tunable magnetism can be utilized to design future spintronics based on MXenes

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