Browsing by Department "University of Puerto Rico"

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    Enhanced Ferromagnetism and Tunable Magnetism in Fe3GeTe2Monolayer by Strain Engineering
    (AMERICAN CHEMICAL SOCIETY, 2020-06-10) Hu, Xiaohui; Zhao, Yinghe; Shen, Xiaodong; Krasheninnikov, Arkady V.; Chen, Zhongfang; Sun, Litao; Nanjing Tech University; University of Puerto Rico; Department of Applied Physics; Southeast University, Nanjing
    Recent discovery of intrinsic ferromagnetism in Fe3GeTe2 (FGT) monolayer [ Deng, Y.; et al. Nature 2018, 563, 94-99; Fei, Z.; et al. Nat. Mater. 2018, 17, 778-782 ] not only extended the family of two-dimensional (2D) magnetic materials but also stimulated further interest in the possibility to tune their magnetic properties without changing the chemical composition or introducing defects. By means of density functional theory computations, we explore strain effects on the magnetic properties of the FGT monolayer. We demonstrate that the ferromagnetism can be largely enhanced by the tensile strain in the FGT monolayer due to the competitive effects of direct exchange and superexchange interaction. The average magnetic moments of Fe atoms increase monotonically with an increase in biaxial strain from -5 to 5% in FGT monolayer. The intriguing variation of magnetic moments with strain in the FGT monolayer is related to the charge transfer induced by the changes in the bond lengths. Given the successful fabrication of the FGT monolayer, the strain-tunable ferromagnetism in the FGT monolayer can stimulate the experimental effort in this field. This work also suggests an effective route to control the magnetic properties of the FGT monolayer. The pronounced magnetic response toward the biaxial strain can be used to design the magnetomechanical coupling spintronics devices based on FGT.
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    Enhancing Ferromagnetism and Tuning Electronic Properties of CrI3 Monolayers by Adsorption of Transition-Metal Atoms
    (AMERICAN CHEMICAL SOCIETY, 2021-05-12) Yang, Qiang; Hu, Xiaohui; Shen, Xiaodong; Krasheninnikov, Arkady V.; Chen, Zhongfang; Sun, Litao; Nanjing Tech University; Department of Applied Physics; University of Puerto Rico; Southeast University, Nanjing
    Among first experimentally discovered two-dimensional (2D) ferromagnetic materials, chromium triiodide (CrI3) monolayers have attracted particular attention due to their potential applications in electronics and spintronics. However, the Curie temperature Tc of the CrI3 monolayer is below room temperature, which greatly limits practical development of the devices. Herein, using density functional theory calculation, we explore how the electronic and magnetic properties of CrI3 monolayers change upon adsorption of 3d transition-metal (TM) atoms (from Sc to Zn). Our results indicate that the electronic properties of the TM-CrI3 system can be tuned from semiconductor to metal/half-metal/spin gapless semiconductor depending on the choice of the adsorbed TM atoms. Moreover, the adsorption can improve the ferromagnetic stability of CrI3 monolayers by increasing both magnetic moments and Tc. Notably, Tc of CrI3 with Sc and V adatoms can be increased by nearly a factor of 3. We suggest postsynthesis doping of 2D CrI3by deposition of TM atoms as a new route toward potential applications of TM-CrI3 systems in nanoelectronic and spintronic devices.
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    Tunable electronic properties and enhanced ferromagnetism in Cr2Ge2Te6monolayer by strain engineering
    (IOP Publishing Ltd., 2021-11-26) Liu, Lifei; Hu, Xiaohui; Wang, Yifeng; Krasheninnikov, Arkady V.; Chen, Zhongfang; Sun, Litao; Nanjing Tech University; Department of Applied Physics; University of Puerto Rico; Southeast University, Nanjing
    Recently, as a new representative of Heisenberg's two-dimensional (2D) ferromagnetic materials, 2D Cr2Ge2Te6 (CGT), has attracted much attention due to its intrinsic ferromagnetism. Unfortunately, the Curie temperature (T C ) of CGT monolayer is only 22 K, which greatly hampers the development of the applications based on the CGT materials. Herein, by means of density functional theory computations, we explored the electronic and magnetic properties of CGT monolayer under the applied strain. It is demonstrated that the band gap of CGT monolayer can be remarkably modulated by applying the tensile strain, which first increases and then decreases with the increase of tensile strain. In addition, the strain can increase the Curie temperature and magnetic moment, and thus largely enhance the ferromagnetism of CGT monolayer. Notably, the obvious enhancement of T C by 191% can be achieved at 10% strain. These results demonstrate that strain engineering can not only tune the electronic properties, but also provide a promising avenue to improve the ferromagnetism of CGT monolayer. The remarkable electronic and magnetic response to biaxial strain can also facilitate the development of CGT-based spin devices.