347 research outputs found

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

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    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

    Contents and benthic fluxes of nutrients in sediment pore water of Southern Ocean

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    The concentration and profile characters of nutrients in sediment pore water of the South Ocean, sampled during the cruise of CHINARE218 of the austral summer 2001 /02 were determined. The results show that the content of SiO3-Si and NH4-N were much higher than other nutrients. The profile of SiO3-Si was characterized with sharp gradients near the sediment-water interface, profile distribution of silicate show that during the diagenetic reaction of silicate, dissolution was the main part. The organic matter decomposition was occurred under the anaerobic condition. Benthic fluxes of SiO3-Si, NH4-N were from pore water to overlying water, and regeneration of silicate and ammonium were the main part of the nutrient regeneration from the pore water of the study area