具有室温铁磁性的二维Janus钛硫属化物★

doi:10.6023/A23050194

摘要/Abstract

设计具有室温磁性的二维铁磁材料是发展纳米尺度自旋电子学器件的重要基础, 但目前实验合成的二维室温铁磁体种类有限且鲜有报道如何从非磁材料设计室温铁磁体. 受近期实验合成Janus MoSSe单层结构的启发, 基于第一性原理计算理论预测了一类具有新奇电子结构的二维室温铁磁体Janus TiXY (X=S、Se和Te; Y=H和F). 声子谱计算和分子动力学模拟表明这些Janus单层材料具有晶格动力学和热力学稳定性. 基于HSE06杂化泛函计算能带结构给出单层TiTeH和TiTeF是带隙为0.18和0.48 eV的双极磁性半导体, 其中TiTeH由于存在巨磁能带结构效应可以通过将自旋取向由面外翻转至面内实现能带交错-打开转变和自旋分裂调控, 即达到自旋取向调控能带结构. 单层TiSH、TiSeH、TiSF和TiSeF分别是自旋带隙为2.67、1.73、3.11和2.27 eV的铁磁半金属材料. 蒙特卡洛模拟给出TiXH和TiXF的居里温度范围分别为339~401 K和341~497 K, 表明这些Janus单层材料均具有室温铁磁性. 我们还发现在双层TiSF中存在与双层CrI₃类似的堆积取向依附的层间磁耦合基态. 此外当选用石墨烯作为保护层与TiXY形成异质结后单层Janus结构的本征电子结构特征可以保留. 室温铁磁性以及丰富且可调控的电子结构使Janus TiXY材料成为一类理想的自旋电子学候选材料, 同时基于非磁材料构建Janus结构为设计新型二维铁磁体开辟了一条崭新途径.

关键词: Janus单层材料, 第一性原理, 室温铁磁性, 电子结构, 异质结

Design of two-dimensional (2D) ferromagnetic materials with room-temperature magnetism is basic cornerstone for developing nanoscale spintronics. However, the experimental realized room-temperature ferromagnets are very limited and the design of room-temperature ferromagnets based on non-magnetic materials is rarely reported. Motivated by recently synthesized Janus MoSSe monolayer, we have predicted that Janus TiXY (X=S, Se and Te; Y=H and F) monolayers are intrinsic 2D ferromagnetic materials with above room-temperature long-range spin ordering and diverse electronic structures based on systematically first-principles calculations. The six Janus TiXY monolayers tend to adopt T-phase symmetry. The dynamically and thermally stability of lattice are confirmed by phonon spectrum calculations and molecular dynamics simulations. Band structure calculations at HSE06 functional level demonstrate that the monolayer TiTeH and TiTeF are bipolar ferromagnetic semiconductors (BMS) with bandgap of 0.18 and 0.48 eV, respectively. Further, the spin direction-controlled band crossing to band gaped transition and tunable spin splitting at Γ-point are observed in TiTeH monolayer after flipping the spin orientation along from out-of-plane to in-plane direction owing to giant magneto band-structure effect. The TiSH, TiSeH, TeSF, and TiSeF monolayers are half-metallic ferromagnets (HMF) with a large spin gap of 2.67, 1.73, 3.11, and 2.27 eV, respectively. Especially, the estimated Curie temperature (T_c) of TiXH and TiXF based on Monte Carlo simulations are range from 339~401 K and 341~497 K, respectively, which are higher than room-temperature. Similar to bilayer CrI₃, we also find a stacking configuration dependent interlayer magnetic coupling ground state in bilayer TiSF. Moreover, taking TiSH and TiSF as prototypes, the intrinsic electronic properties can be maintained after the formation of heterojunctions by applying a protective coating graphene layer. The intrinsic room-temperature ferromagnetism together with diverse electronic structures, making the Janus TiXY monolayer a promising candidate for realistic spintronic applications. Further, constructing Janus monolayers based on nonmagnetic materials opens up new pathway for designing novel 2D ferromagnets.

Key words: Janus monolayer, first-principles, room-temperature ferromagnetism, electronic structures, heterojunction

引用此文

张凯, 武晓君. 具有室温铁磁性的二维Janus钛硫属化物^★[J]. 化学学报, 2023, 81(9): 1142-1147.

Kai Zhang, Xiaojun Wu. Room-Temperature Ferromagnetism in Two-Dimensional Janus Titanium Chalcogenides^★[J]. Acta Chimica Sinica, 2023, 81(9): 1142-1147.

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图/表 6

图1. (a)和(b)分别为T和H相Janus TiXY单层结构. (c)和(d)分别为TiSH和TiSF的差分电荷密度图, 等值面分别为0.03和0.05 e/Bohr3,其中电子消耗和集聚区域分别用红色和蓝色显示. 俯视和侧视图分别展示在左侧和右侧

Figure 1. Structures of the (a) T-phase and (b) H-phase Janus TiXY monolayers. Isosurface plots of deformation electronic density of (c) TiSH and (d) TiSF monolayers with charge depletion and accumulation regions colored red and blue, respectively. The isovalue are equal to 0.03 and 0.05 e/Bohr3 for TiSH and TiSF, respectively. The top and side views are displayed in left and right panels

TiXY	ΔE/eV	a/nm	G.S	M/µ_B	E_f/eV
TiSH	–0.319	0.322	HMF^a	0.84	–0.233
TiSeH	–0.351	0.329	HMF^a	0.87	–0.244
TiTeH	–0.223	0.336	BMS^b	0.88	–0.487
TiSF	–0.147	0.328	HMF^a	0.92	–2.138
TiSeF	–0.117	0.335	HMF^a	1.00	–2.126
TiTeF	–0.107	0.349	BMS^b	1.11	–2.258

表1. T相和H相TiXY单层结构每单胞的能量差ΔE=ET–EH, 优化后的晶格常数a, 基态电子结构特征G.S, 每单胞磁矩M和形成能Ef

Table 1. The calculated energy difference (ΔE=ET–EH) between T-phase and H-phase monolayer TiXY per Ti atom, optimized lattice constant a, ground state electronic configuration (G.S), magnetic moment M, and formation energy per Ti atom Ef

图2. (a)和(b)分别为TiSH和TiSF单层结构的声子谱. (c)和(d)分别为模拟过程中TiSH和TiSF的能量和温度随模拟时间的变化以及在300 K下模拟5 ps后的瞬态结构, 其中模拟结束后结构的俯视图和侧视图分别展现在左侧和右侧

Figure 2. The phonon spectra of (a) TiSH and (b) TiSF monolayers. The evolution of total energy and temperature during the simulations and the structure snapshot at 300 K after 5 ps simulation are shown in (c) and (d), the top and side views are displayed in left and right panels, respectively

图3. (a~d)分别为TiSH, TiSF, TiTeH和TiTeF单层的能带结构和态密度图, 其中能带图中自旋向上和向下分别用红色和蓝色显示

Figure 3. (a~d) The spin resolved band structures and projected density of states of TiSH, TiSF, TiTeH, and TiTeF monolayers, the majority and minority spin are displayed in red and blue colors.

图4. (a)和(b)分别为TiSH和TiSF单层的自旋电荷密度分布, 相应等值面为0.01 e/Bohr3. 蒙特卡洛模拟(c) TiSH和(d) TiSF磁矩M和比热Cv随温度的变化

Figure 4. The spin charge density distribution for (a) TiSH and (b) TiSF monolayers, the isovalue is 0.01 e/Bohr3. The simulated magnetic moment (M) and specific heat (Cv) with respect to temperature for (c) TiSH and (d) TiSF monolayers

图5. 自旋取向分别沿(a)面外和(b)面内方向时单层TiTeH的能带结构, 红色和蓝色圈分别标记出能带交错-打开转变和能带自旋分裂, 红色箭头表示自旋取向

Figure 5. The band structures of Janus TiTeH monolayer with spin direction along (a) out-of-plane and (b) in-plane. The red and blue circles highlight the band crossing become band gaped and spin splitting when spin direction changed, the red arrows represent the spin direction

参考文献 43

[1]	Wolf, S.; Awschalom, D.; Buhrman, R.; Daughton, J.; Von Molnar, S.; Roukes, M.; Chtchelkanova, A. Y.; Treger, D. Science 2001, 294, 1488. pmid: 11711666
[2]	Fert, A. Rev. Mod. Phys. 2008, 80, 1517. doi: 10.1103/RevModPhys.80.1517
[3]	Zhang, Q.; Jiang, M. Y.; Liu, T. Y.; Zeng, Y. X.; Shi, S. W. Acta Chim. Sinica 2022, 80, 1351. (in Chinese) doi: 10.6023/A22050212
	(张琪, 江梦云, 刘天一, 曾意迅, 石胜伟, 化学学报, 2022, 80, 1351.) doi: 10.6023/A22050212
[4]	Li, X.; Yang, J. Chin. J. Chem. 2019, 37, 1021. doi: 10.1002/cjoc.v37.10
[5]	Ando, K. Science 2006, 312, 1883. doi: 10.1126/science.1125461
[6]	De Groot, R.; Mueller, F.; Van Engen, P.; Buschow, K. Phys. Rev. Lett. 1983, 50, 2024. doi: 10.1103/PhysRevLett.50.2024
[7]	Huang, B.; Clark, G.; Navarro-Moratalla, E.; Klein, D. R.; Cheng, R.; Seyler, K. L.; Zhong, D.; Schmidgall, E.; McGuire, M. A.; Cobden, D. H. Nature 2017, 546, 270. doi: 10.1038/nature22391
[8]	Gong, C.; Li, L.; Li, Z.; Ji, H.; Stern, A.; Xia, Y.; Cao, T.; Bao, W.; Wang, C.; Wang, Y.; Qiu, Z. Q.; Cava, R. J.; Louie, S. G.; Xia, J.; Zhang, X. Nature 2017, 546, 265. doi: 10.1038/nature22060
[9]	Bonilla, M.; Kolekar, S.; Ma, Y.; Diaz, H. C.; Kalappattil, V.; Das, R.; Eggers, T.; Gutierrez, H. R.; Phan, M.-H.; Batzill, M. Nat. Nanotechnol. 2018, 13, 289. doi: 10.1038/s41565-018-0063-9 pmid: 29459653
[10]	Fei, Z.; Huang, B.; Malinowski, P.; Wang, W.; Song, T.; Sanchez, J.; Yao, W.; Xiao, D.; Zhu, X.; May, A. F. Nat. Mater. 2018, 17, 778. doi: 10.1038/s41563-018-0149-7
[11]	O’Hara, D. J.; Zhu, T.; Trout, A. H.; Ahmed, A. S.; Luo, Y. K.; Lee, C. H.; Brenner, M. R.; Rajan, S.; Gupta, J. A.; McComb, D. W. Nano Lett. 2018, 18, 3125. doi: 10.1021/acs.nanolett.8b00683
[12]	Kong, T.; Stolze, K.; Timmons, E. I.; Tao, J.; Ni, D.; Guo, S.; Yang, Z.; Prozorov, R.; Cava, R. J. Adv. Mater. 2019, 1808074.
[13]	Lu, A.-Y.; Zhu, H.; Xiao, J.; Chuu, C.-P.; Han, Y.; Chiu, M.-H.; Cheng, C.-C.; Yang, C.-W.; Wei, K.-H.; Yang, Y. Nat. Nanotechnol. 2017, 12, 744. doi: 10.1038/nnano.2017.100
[14]	Zhang, J.; Jia, S.; Kholmanov, I.; Dong, L.; Er, D.; Chen, W.; Guo, H.; Jin, Z.; Shenoy, V. B.; Shi, L. ACS Nano 2017, 11, 8192. doi: 10.1021/acsnano.7b03186 pmid: 28771310
[15]	Er, D.; Ye, H.; Frey, N. C.; Kumar, H.; Lou, J.; Shenoy, V. B. Nano Lett. 2018, 18, 3943. doi: 10.1021/acs.nanolett.8b01335
[16]	Chen, W.; Qu, Y.; Yao, L.; Hou, X.; Shi, X.; Pan, H. J. Mater. Chem. A 2018, 6, 8021. doi: 10.1039/C8TA01202D
[17]	Zhang, C.; Nie, Y.; Sanvito, S.; Du, A. Nano Lett. 2019, 19, 1366. doi: 10.1021/acs.nanolett.8b05050
[18]	Peng, R.; Ma, Y.; Zhang, S.; Huang, B.; Dai, Y. J. Phys. Chem. Lett. 2018, 9, 3612. doi: 10.1021/acs.jpclett.8b01625 pmid: 29909617
[19]	Wang, Z. J. Mater. Chem. C 2018, 6, 13000. doi: 10.1039/C8TC04951C
[20]	Jena, N.; Rawat, A.; Ahammed, R.; Mohanta, M. K.; De Sarkar, A. J. Mater. Chem. A 2018, 6, 24885. doi: 10.1039/C8TA08781D
[21]	Dong, L.; Lou, J.; Shenoy, V. B. ACS Nano 2017, 11, 8242. doi: 10.1021/acsnano.7b03313
[22]	Sun, Y.; Shuai, Z.; Wang, D. Nanoscale 2018, 10, 21629. doi: 10.1039/C8NR08151D
[23]	Hu, T.; Jia, F.; Zhao, G.; Wu, J.; Stroppa, A.; Ren, W. Phys. Rev. B 2018, 97, 235404. doi: 10.1103/PhysRevB.97.235404
[24]	Wu, D.; Zhuo, Z.; Lv, H.; Wu, X. J. Phys. Chem. Lett. 2021, 12, 2905. doi: 10.1021/acs.jpclett.1c00454
[25]	Zhou, X.; Sun, X.; Zhang, Z.; Guo, W. J. Mater. Chem. C 2018, 6, 9675. doi: 10.1039/C8TC03016B
[26]	Li, X.; Wu, X.; Li, Z.; Yang, J.; Hou, J. Nanoscale 2012, 4, 5680. doi: 10.1039/c2nr31743e
[27]	Goodenough, J. B. Phys. Rev. 1955, 100, 564. doi: 10.1103/PhysRev.100.564
[28]	Anderson, P. W. Phys. Rev. 1950, 79, 350. doi: 10.1103/PhysRev.79.350
[29]	Kanamori, J. J. Phys. Chem. Solids 1959, 10, 87. doi: 10.1016/0022-3697(59)90061-7
[30]	Fong, C. Y.; Qian, M. C.; Liu, K.; Yang, L. H.; Pask, J. E. J. Nanosci. Nanotechnol. 2008, 8, 3652. pmid: 19051923
[31]	Jiang, P.; Li, L.; Liao, Z.; Zhao, Y.; Zhong, Z. Nano Lett. 2018, 18, 3844. doi: 10.1021/acs.nanolett.8b01125
[32]	Sivadas, N.; Okamoto, S.; Xu, X.; Fennie, C. J.; Xiao, D. Nano Lett. 2018, 18, 7658. doi: 10.1021/acs.nanolett.8b03321 pmid: 30408960
[33]	Xiong, Q.; Zhou, J.; Zhang, J.; Kitamura, T.; Li, Z. Phys. Chem. Chem. Phys. 2018, 20, 20988. doi: 10.1039/C8CP02011F
[34]	Kresse, G.; Furthmüller, J. Phys. Rev. B 1996, 54, 11169. doi: 10.1103/physrevb.54.11169 pmid: 9984901
[35]	Kresse, G.; Joubert, D. Phys. Rev. B 1999, 59, 1758. doi: 10.1103/PhysRevB.59.1758
[36]	Blöchl, P. E. Phys. Rev. B 1994, 50, 17953. doi: 10.1103/PhysRevB.50.17953
[37]	Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996, 77, 3865. doi: 10.1103/PhysRevLett.77.3865 pmid: 10062328
[38]	Heyd, J.; Scuseria, G. E.; Ernzerhof, M. J. Chem. Phys. 2003, 118, 8207. doi: 10.1063/1.1564060
[39]	Dudarev, S.; Botton, G.; Savrasov, S.; Humphreys, C.; Sutton, A. Phys. Rev. B 1998, 57, 1505. doi: 10.1103/PhysRevB.57.1505
[40]	Klimeš, J.; Bowler, D. R.; Michaelides, A. J. Phys.: Condens. Matter 2009, 22, 022201. doi: 10.1088/0953-8984/22/2/022201
[41]	Klimeš, J.; Bowler, D. R.; Michaelides, A. Phys. Rev. B 2011, 83, 195131. doi: 10.1103/PhysRevB.83.195131
[42]	Togo, A.; Tanaka, I. Scr. Mater. 2015, 108, 1. doi: 10.1016/j.scriptamat.2015.07.021
[43]	Kresse, G.; Hafner, J. Phys. Rev. B 1993, 47, 558. doi: 10.1103/physrevb.47.558 pmid: 10004490