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The effective control of two-dimensional material magnetism is a frontier research field. In this work, the influences of in-plane biaxial tension strain on the electronic structure, magnetic properties, and Curie temperature of monolayer NbSi2N4 are investigated by first-principles calculations based on density functional theory and Monte Carlo simulations in the frame of the Heisenberg model. We demonstrate that the monolayer NbSi2N4 has favorable dynamic and thermal stability through the phonon spectral calculations and ab initio molecular dynamics simulations. It is found that the intrinsic monolayer NbSi2N4 is a non-magnetic metal, which can be transformed into a ferromagnetic metal by 1.5% tensile strain. The electronic structure analysis of monolayer NbSi2N4 shows that the ferromagnetism induced by tensile strain is caused by traveling electrons. There is a half-full band at the monolayer NbSi2N4 Fermi level, which is mainly contributed by the dz2 orbital of the Nb atom. When there is no additional strain, the band is spin-degenerate. Tensile strain can make this band more localized, which leads to Stoner instability, resulting in the ferromagnetic ordering of monolayer NbSi2N4 traveling electrons. The stability of the ferromagnetic coupling is enhanced with the increase of the strain degree. The calculation results of the magnetic anisotropy energy show that the strain can make the direction of the easy magnetization axis of the monolayer NbSi2N4 reverse from the vertical direction to the in-plane, and then back to the vertical direction. Furthermore, the strain can significantly increase the Curie temperature of monolayer NbSi2N4. The Curie temperature of monolayer NbSi2N4 is 18 K at 2% strain and 87.5 K at 6% strain, which is 386% higher than that at 2% strain. Strain engineering can effectively control the magnetic ground state and Curie temperature of single-layer NbSi2N4. The research results are expected to promote the development of MA2Z4 materials in the field of mechanical sensing device design and low-temperature magnetic refrigeration.
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Keywords:
- two dimensional material /
- first-principle /
- magnetism /
- strain
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[3] Choudhuri I, Bhauriyal P, Pathak B 2019 Chem. Mater. 31 8260Google Scholar
[4] Sun Y J, Zhuo Z W, Wu X J, Yang J L 2017 Nano Lett. 17 2771Google Scholar
[5] Miao Y P, Huang Y H, Fang Q L, Yang Z, Xu K W, Ma F, Chu P K 2016 J. Mater. Sci. 51 9514Google Scholar
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[8] Eean F, Arkin H, Aktürk E 2017 RSC Adv. 7 37815Google Scholar
[9] Huang B, Clark G, Navarro-Moratalla E, Klein D, Cheng R, Seyler K, Zhong D, Schmidgall E, McGuire M, Cobden D, Yao W, Xiao D, Jarillo-Herrero P, Xu X D 2017 Nature 546 270Google Scholar
[10] Gong C, Li L, Li Z L, Ji H W, Stern A, Xia Y, Cao T, Bao W, Wang C Z, Wang Y, Qiu Z Q, Cava R J, Louie S G, Xia J, Zhang X 2017 Nature 546 265Google Scholar
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[12] Hong Y L, Liu Z, Wang L, Zhou T, Ma W, Xu C, Feng S, Chen L, Chen M L, Sun D M, Chen X Q, Cheng H M, Ren W 2020 Science 369 670Google Scholar
[13] Novoselov K S 2020 Natl. Sci. Rev. 7 1842Google Scholar
[14] Yang C, Song Z, Sun X, Lu J 2021 Phys. Rev. B 103 035308Google Scholar
[15] Yang J S, Zhao L N, Li S Q, Liu H S, Wang L, Chen M D, Gao J F, Zhao J J 2021 Nanoscale 13 5479Google Scholar
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[17] Guo S D, Mu W Q, Zhu Y T, Chen X Q 2020 Phys. Chem. Chem. Phys. 22 28359Google Scholar
[18] Li F, Ren Y L, Wan W H, Liu Y, Ge Y F 2021 AIP Advances 11 115220Google Scholar
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[22] Wu Z B, Shen Z, Xue Y F, Song C S 2022 Phys. Rev. Mater. 6 014011Google Scholar
[23] Qin H F, Chen J, Sun B, Tang Y L, Ni Y X, Chen Z F, Wang H Y, Chen Y Z 2021 Phys. Chem. Chem. Phys. 23 22078Google Scholar
[24] Liu L F, Hu X H, Wang Y F, Krasheninnikov A V, Chen Z F, Sun L T 2021 Nanotechnology 32 485408Google Scholar
[25] Xie W Q, Lu Z W, He C C, Yang X B, Zhao Y J 2021 J. Phys. Condens. Matter 33 215803Google Scholar
[26] Kresse G, Furthmüller J 1996 Comput. Mater. Sci. 6 15Google Scholar
[27] Kresse G, Furthmüller J, Hafner J 1994 Phys. Rev. B 50 13181Google Scholar
[28] Perdew J P, Burke K, Ernzerhof M 1996 Phys. Rev. Lett. 77 3865Google Scholar
[29] Kresse G, Joubert D 1999 Phys. Rev. B 59 1758
[30] Monkhorst H J, Pack J D 1976 Phys. Rev. B 13 5188Google Scholar
[31] Togo A, Oba F, Tanaka I 2008 Phys. Rev. B 78 134106Google Scholar
[32] Joyce G 1967 Phys. Rev. 155 478Google Scholar
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[34] Duong D L, Burghard M, Schön J C 2015 Phys. Rev. B 92 245131Google Scholar
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图 1 (a)单层NbSi2N4的俯视图(左)和侧视图(右), 自旋密度分布用黄色表示; (b)不考虑自旋极化时单层NbSi2N4的能带结构和态密度图; (c)单层NbSi2N4的声子谱图; (d)温度300 K, 时长10 ps的分子动力学模拟下, 系统总能量的变化; (e)考虑自旋极化时单层NbSi2N4的能带结构和态密度图
Figure 1. (a) Top view (left) and side view (right) of monolayer NbSi2N4, and the spin density distribution is represented in yellow; (b) energy band structure and density of states of monolayer NbSi2N4 without considering spin polarization; (c) phonon spectra of monolayer NbSi2N4; (d) the change of total energy of the system under the molecular dynamics simulation of temperature 300 K and duration 10 ps; (e) energy band structure and density of states of monolayer NbSi2N4 considering spin polarization.
图 2 (a)单层NbSi2N4铁磁态与无磁态间的能量差随电子温度的变化关系; (b)单层NbSi2N4在2%应变下的声子谱; (c) 单层NbSi2N4 6%应变下的声子谱
Figure 2. (a) Variation of energy difference between ferromagnetic and nonmagnetic states of monolayer NbSi2N4 with electron temperature; (b) the phonon spectrum of monolayer NbSi2N4 at 2% strain; (c) the phonon spectrum of monolayer NbSi2N4 at 6% strain.
图 3 (a) 单层NbSi2N4反铁磁态和铁磁态与无磁态间能量差随应变变化; (b)单层NbSi2N4磁矩随应变变化; (c) MAE随应变变化; (d)不同应变下, Nb原子轨道磁矩与自旋磁矩对MAE的贡献
Figure 3. (a) Energy difference between antiferromagnetic state, ferromagnetic state and non-magnetic state of monolayer NbSi2N4 with strain; (b) magnetic moment of monolayer NbSi2N4 with strain; (c) MAE with strain; (d) contribution of orbital magnetic moment and spin magnetic moment of Nb atom to MAE under different strains.
图 4 (a) 单层NbSi2N4分波态密度; (b)—(e) 单层NbSi2N4在不同应变下的态密度; (f)铁磁态与无磁态间的能量差随磁矩变化的DFT计算曲线, 将无磁态的能量设为0 meV
Figure 4. (a) Fractional density of states of monolayer NbSi2N4. (b)–(e) The density of state of monolayer NbSi2N4 under different strains. (f) DFT calculation curve of the energy difference between the FM state and the NM state change with the magnetic moment, the energy of the NM state is set to 0 meV.
表 1 在不同应变下的交换常数J和各向异性参数D
Table 1. Exchange constant J and anisotropy parameter D under different strains.
应变/% 2 3 4 5 6 J/meV –2.430 –5.625 –8.767 –12.109 –16.753 D/meV 1.224 –0.248 0.388 0.596 0.468 -
[1] Jansen R 2012 Nat. Mater. 11 400Google Scholar
[2] Lin X Y, Yang W, Wang K L, Zhao W S 2019 Nat. Electron. 2 274Google Scholar
[3] Choudhuri I, Bhauriyal P, Pathak B 2019 Chem. Mater. 31 8260Google Scholar
[4] Sun Y J, Zhuo Z W, Wu X J, Yang J L 2017 Nano Lett. 17 2771Google Scholar
[5] Miao Y P, Huang Y H, Fang Q L, Yang Z, Xu K W, Ma F, Chu P K 2016 J. Mater. Sci. 51 9514Google Scholar
[6] Kaloni T P 2014 J. Phys. Chem. C 118 25200Google Scholar
[7] Mao Y L, Guo G, Yuan J M, Zhong J X 2019 Appl. Surf. Sci. 464 236Google Scholar
[8] Eean F, Arkin H, Aktürk E 2017 RSC Adv. 7 37815Google Scholar
[9] Huang B, Clark G, Navarro-Moratalla E, Klein D, Cheng R, Seyler K, Zhong D, Schmidgall E, McGuire M, Cobden D, Yao W, Xiao D, Jarillo-Herrero P, Xu X D 2017 Nature 546 270Google Scholar
[10] Gong C, Li L, Li Z L, Ji H W, Stern A, Xia Y, Cao T, Bao W, Wang C Z, Wang Y, Qiu Z Q, Cava R J, Louie S G, Xia J, Zhang X 2017 Nature 546 265Google Scholar
[11] Wang L, Shi Y P, Liu M F, et al. 2021 Nat. Commun. 12 2361
[12] Hong Y L, Liu Z, Wang L, Zhou T, Ma W, Xu C, Feng S, Chen L, Chen M L, Sun D M, Chen X Q, Cheng H M, Ren W 2020 Science 369 670Google Scholar
[13] Novoselov K S 2020 Natl. Sci. Rev. 7 1842Google Scholar
[14] Yang C, Song Z, Sun X, Lu J 2021 Phys. Rev. B 103 035308Google Scholar
[15] Yang J S, Zhao L N, Li S Q, Liu H S, Wang L, Chen M D, Gao J F, Zhao J J 2021 Nanoscale 13 5479Google Scholar
[16] Chen J, Tang Q 2021 Chem. Eur. J. 27 9925Google Scholar
[17] Guo S D, Mu W Q, Zhu Y T, Chen X Q 2020 Phys. Chem. Chem. Phys. 22 28359Google Scholar
[18] Li F, Ren Y L, Wan W H, Liu Y, Ge Y F 2021 AIP Advances 11 115220Google Scholar
[19] Zheng F W, Zhao J Z, Liu Z, Li M L, Zhou M, Zhang S B, Zhang P 2018 Nanoscale 10 14298Google Scholar
[20] Wu Z W, Yu J, Yuan S J 2019 Phys. Chem. Chem. Phys. 21 7750Google Scholar
[21] Chen T, Liu G G, Dong X S, Li H L, Zhou G H 2022 J. Electron. Mater. 51 2212Google Scholar
[22] Wu Z B, Shen Z, Xue Y F, Song C S 2022 Phys. Rev. Mater. 6 014011Google Scholar
[23] Qin H F, Chen J, Sun B, Tang Y L, Ni Y X, Chen Z F, Wang H Y, Chen Y Z 2021 Phys. Chem. Chem. Phys. 23 22078Google Scholar
[24] Liu L F, Hu X H, Wang Y F, Krasheninnikov A V, Chen Z F, Sun L T 2021 Nanotechnology 32 485408Google Scholar
[25] Xie W Q, Lu Z W, He C C, Yang X B, Zhao Y J 2021 J. Phys. Condens. Matter 33 215803Google Scholar
[26] Kresse G, Furthmüller J 1996 Comput. Mater. Sci. 6 15Google Scholar
[27] Kresse G, Furthmüller J, Hafner J 1994 Phys. Rev. B 50 13181Google Scholar
[28] Perdew J P, Burke K, Ernzerhof M 1996 Phys. Rev. Lett. 77 3865Google Scholar
[29] Kresse G, Joubert D 1999 Phys. Rev. B 59 1758
[30] Monkhorst H J, Pack J D 1976 Phys. Rev. B 13 5188Google Scholar
[31] Togo A, Oba F, Tanaka I 2008 Phys. Rev. B 78 134106Google Scholar
[32] Joyce G 1967 Phys. Rev. 155 478Google Scholar
[33] Liu L, Chen S S, Lin Z Z, Zhang X 2020 J. Phys. Chem. Lett. 11 7893Google Scholar
[34] Duong D L, Burghard M, Schön J C 2015 Phys. Rev. B 92 245131Google Scholar
[35] Van Vleck J H 1937 Phys. Rev. 52 1178Google Scholar
[36] Sieberer M, Khmelevskyi S, Mohn P 2006 Phys. Rev. B 74 014416Google Scholar
[37] Zhuang H L L, Kent P R C, Hennig R G 2016 Phys. Rev. B 93 134407Google Scholar
[38] Kulish V V, Huang W 2017 J. Mater. Chem. C 5 8734Google Scholar
[39] Zhao Y, Liu Q X, Xing J P, Jiang X, Zhao J J 2022 Nanoscale Adv. 4 600Google Scholar
[40] Sun X Y, Yang K, Li Z Y 2022 Phys. Status Solidi RRL 16 2100611Google Scholar
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