-
半金属铁磁体在费米能级附近具有特殊的能带结构，电子极化率可高达100%，在自旋电子学领域备受关注。但是大部分铁磁半金属材料的居里温度远低于室温，这大大限制了二维铁磁半金属材料的实际应用。因此寻找具有高居里温度的半金属铁磁体是一项具有挑战性的工作。本文基于密度泛函理论框架下的第一性原理方法，研究了过渡金属氧化物CrO2单层的晶体结构、电子特性、基态磁性和铁磁相变。形成能计算、声子谱计算和分子动力学模拟表明CrO2具有动力学稳定性和热稳定性，弹性常数计算表明CrO2具有力学稳定性。基于GGA + U和SCAN方法的自旋极化计算表明CrO2单层的磁基态是铁磁态。采用GGA + U方法计算了CrO2的电子态密度和能带结构，CrO2被确认为一种宽带隙的二维铁磁半金属。运用蒙特卡罗模拟方法求解Heisenberg模型，得到CrO2单层是一种居里温度超过400 K的二维本征半金属铁磁体。CrO2单层的高居里温度在二维铁磁材料中并不多见，在半金属材料中更为稀少，这将使它成为制备自旋电子器件和研究自旋量子效应的理想材料。Owing to the complete spin-polarization of electronic states near Fermi energy, half-metallic ferromagnets, especially two-dimensional half-metallic ferromagnets, have garnered significant attention in the field of spintronics. However, the practical application of these materials is greatly hindered by their low Curie temperatures. Therefore, the exploration of high Curie temperature half-metallic ferromagnets poses a necessary and challenging task. In this study, we predict a two-dimensional transition metal oxide, CrO2 monolayer, and employed first-principles calculations to investigate the crystal structure, electronic properties, magnetic ground state, and ferromagnetic phase transition. The calculations on phonon spectrum, elastic constant, and molecular dynamics simulations indicate that CrO2 monolayer is dynamically, thermally, and mechanically stable. The convex hull diagram of Cr-O systems shows the hull energy of the predicted CrO2 layer is only 0.18 eV, further confirming the structural stability and large possibility for experimental fabrication. More importantly, the electronic and magnetic properties of CrO2 monolayer demonstrate that it is a two-dimensional ferromagnetic half-metal with wide band gap. Five d suborbitals are divided into eg and t2g orbitals because of the crystal field of Cr atom at the center of O tetrahedron, and the spin-polarization of eg orbitals make a major contribution to the moment around Cr atom. The ferromagnetic coupling along Cr-O-Cr chain is dominated by the superexchange interaction bridged by O 2p orbital, similar to the typical Mn-O-Mn superexchange model. The magnetic behavior of the Cr spin lattice in a CrO2 monolayer is described by a two-dimensional Heisenberg model, in which the exchange coupling anisotropy is ignored and the single ion anisotropy is the main consideration. By solving the Heisenberg model using the Monte Carlo simulation method, the Curie temperature is determined to be over 400 K. The high Curie temperature ferromagnetism is rare in two-dimensional ferromagnetic materials and even rarer in semi-metallic materials, which makes it an ideal material for the fabrication of spintronic devices and the study of spin quantum effects.
-
Keywords:
- Transition metal oxide /
- Two-dimensional ferromagnetic half-metal /
- Curie temperature /
- First-principles theory
-
[1] Novoselov K S, Geim A K, Morozov S V, Jiang D, Zhang Y, Dubonos S V, Grigorieva I V, Firsov A A 2004 Science 306 666
[2] Zhang H 2015 ACS Nano 9 9451
[3] 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 546 265
[4] 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, Yao W, Xiao D, Jarillo-Herrero P, Xu X 2017 Nature 546 270
[5] Gong C, Zhang X 2019 Science 363 eaav4450
[6] Balan A P, Radhakrishnan S, Woellner C F, Sinha S K, Deng L, de los Reyes C, Rao B M, Paulose M, Neupane R, Apte A, Kochat V, Vajtai R, Harutyunyan A R, Chu C W, Costin G, Galvao D S, Martí A A, van Aken P A, Varghese O K, Tiwary C S, Iyer A M M R, Ajayan P M 2018 Nat. Nanotechnol. 13 602
[7] Balan A P, Radhakrishnan S, Kumar R, Neupane R, Sinha S K, Deng L Z, de los Reyes C A, Apte A, Rao B M, Paulose M, Vajtai R, Chu C W, Costin G, Martí A A, Varghese O K, Singh A K, Tiwary C S, Anantharaman M R, Ajayan P M 2018 Chem. Mater. 30 5923
[8] Zhang Y, Chu J W, Yin L, Shifa T A, Cheng Z Z, Cheng R Q, Wang F, Wen Y, Zhan X Y, Wang Z X, He J 2019 Adv. Mater. 31 1900056
[9] Wang H D, Lei P H, Mao X Y, Kong X, Ye X Y, Wang P F, Wang Y, Qin X, Meijer J, Zeng H L, Shi F Z, Du J F 2022 Chin. Phys. Lett. 39 047601
[10] Feng P J, Zhang X H, Zhang S, Liu D P, Gao M, Ma F J, Yan X W, Xie Z Y 2022 ACS Omega 7 43316
[11] Liu D P, Zhang S, Gao M, Yan X W, Xie Z Y 2021 Appl. Phys. Lett. 118 223104
[12] Feng P J, Zhang S, Liu D P, Gao M, Ma F J, Yan X W, Xie Z Y 2022 J. Phys. Chem. C 126 10139
[13] Liu D P, Zhang S, Gao M, Yan X W 2021 Phys. Rev. B 103 125407
[14] Zhang S, Feng P J, Liu D P, Wu H F, Gao M, Xu T S, Xie Z Y, Yan X W 2022 Phys. Rev. B 106 235402
[15] Wang Y, Guo Y, Wang Z K, Fu L, Zhang Y, Xu Y J, Yuan S J, Pan H Z, Du Y W, Wang J L, Tang N J 2021 ACS Nano 15 12069
[16] Wang Y, Xu W, Fu L, Zhang Y, Wu Y Z, Wu L T, Yang D Y, Peng S Z, Ning J, Zhang C, Cui X, Zhong W, Liu Y, Xiong Q H, Han G Q, Hao Y 2023 ACS Appl. Mater. Interfaces 15 54797
[17] Wang Y, Xu W, Yang D Y, Zhang Y, Xu Y J, Cheng Z X, Mi X K, Wu Y Z, Liu Y, Hao Y, Han G Q 2023 ACS Nano 17 24320
[18] Zha H M, Li W, Zhang G J, Liu W J, Deng L W, Jiang Q, Ye M, Wu H, Chang H X, Qiao S 2023 Chin. Phys. Lett. 40 087501
[19] Huang P, Zhang P, Xu S G, Wang H D, Zhang X W, Zhang H 2020 Nanoscale 12 2309
[20] Lin Z C, Peng Y X, Wu B C, Wang C S, Luo Z C, Yang J B 2022 Chin. Phys. B 31 087506
[21] Cava R J 2000 J. Am. Ceram. Soc. 83 5
[22] Wilson R M 2019 Phys. Today 72 19
[23] Chen H H, Yang Y F, Zhang G M, Liu H Q 2023 Nat. Commun. 14 5477
[24] Rasmussen F A, Thygesen K S 2015 J. Phys. Chem. C 119 13169
[25] Topsakal M, Cahangirov S, Bekaroglu E, Ciraci S 2009 Phys. Rev. B 80 235119
[26] Yang J, Jiang Y L, Li L J, Muhire E, Gao M Z 2016 Nanoscale 8 8170
[27] Zhang F, Zhu J J, Zhang D L, Schwingenschlögl U, Alshareef H N 2017 Nano Lett. 17 1302
[28] de Groot R A, Mueller F M, van Engen P G, Buschow K H J 1983 Phys. Rev. Lett. 50 2024
[29] Wolf S A, Awschalom D D, Buhrman R A, Daughton J M, von Molnár S, Roukes M L, Chtchelkanova A Y, Treger D M 2001 Science 294 1488
[30] Schwarz K 1986 J. Phys. F: Met. Phys. 16 L211
[31] Dedkov Yu S, Rüdiger U, Güntherodt G 2002 Phys. Rev. B 65 064417
[32] Ji Y, Strijkers G J, Yang F Y, Chien C L, Byers J M, Anguelouch A, Xiao G, Gupta A 2001 Phys. Rev. Lett. 86 5585
[33] Xie W H, Liu B G, Pettifor D G 2003 Phys. Rev. B 68 134407
[34] Cheng Z M, Wang X Q, Wang F, Lu L Y, Liu G B, Duan Z F, Nie Z X 2011 Acta Phys. Sin. 60 096301(in Chinese) [程志梅, 王新强, 王风, 鲁丽娅, 刘高斌, 段壮芬, 聂招秀2011物理学报60 096301]
[35] Kobayashi K I, Kimura T, Sawada H, Terakura K, Tokura Y 1998 Nature 395 677
[36] Alijani V, Winterlik J, Fecher G H, Naghavi S S, Felser C 2011 Phys. Rev. B 83 184428
[37] Xu J L, Jia L Y, Jin X Q, Hao X N, Ma L, Hou D L 2019 Acta Phys. Sin. 68 157501(in Chinese) [许佳玲, 贾利云, 靳晓庆, 郝兴楠, 马丽, 侯登录2019物理学报68 157501]
[38] Zhao J T, Zhao K, Wang J J, Yu X Q, Yu J, Wu S X 2012 Acta Phys. Sin. 61 213102(in Chinses) [赵建涛, 赵昆, 王家佳, 余新泉, 于金, 吴三械2012物理学报61 213102]
[39] Kresse G, Hafner J 1993 Phys. Rev. B 47 558
[40] Kresse G, Furthmüller J 1996 Phys. Rev. B 54 11169
[41] Blöchl P E 1994 Phys. Rev. B 50 17953
[42] Perdew J P, Burke K, Ernzerhof M 1996 Phys. Rev. Lett. 77 3865
[43] Sun J, Ruzsinszky A, Perdew J P 2015 Phys. Rev. Lett. 115 036402
[44] Dudarev S L, Botton G A, Savrasov S Y, Humphreys C J, Sutton A P 1998 Phys. Rev. B 57 1505
[45] Togo A, Tanaka I 2015 Scr. Mater. 108 1
[46] Martyna G J, Klein M L, Tuckerman M 1992 J. Chem. Phys. 97 2635
[47] Born M, Huang K, Lax M 1955 Am. J. Phys. 23 474
[48] Wooster W A, Wooster N 1931 Nature 127 782
[49] Dufek V, Petrů F, Brožek V 1967 Monatsh. Chem. 98 2424
[50] Zhang Q, Xu M K, Shen Z R, Wei Q 2017 J. Mater. Sci.: Mater. Electron. 28 12056
[51] Zhou S M, Zhu G Y, Wang Y Q, Lou S Y, Hao Y M 2011 Chem. Eng. J. 174 432
[52] Bärnighausen H, Brauer G, Schultz N 1965 Z. Anorg. Allg. Chem. 338 250
[53] Cococcioni M, de Gironcoli S 2005 Phys. Rev. B 71 035105
[54] Henkelman G, Arnaldsson A, Jónsson H 2006 Comput. Mater. Sci. 36 354
[55] de Groot R A, Mueller F M, van Engen P G, Buschow K H J 1983 Phys. Rev. Lett. 50 2024
[56] Sun J, Ruzsinszky A, Perdew J P 2015 Phys. Rev. Lett. 115 036402
[57] Graf T, Felser C, Parkin S S P 2011 Prog. Solid. State Ch. 39 1
[58] Zhang Y H, Wang B, Guo Y, Li Q, Wang J L 2021 Comput. Mater. Sci. 197 110638
[59] Ma F J, Lu Z Y, Xiang T 2008 Phys. Rev. B 78 224517
[60] Xu C, Feng J, Xiang H, Bellaiche L 2018 npj Comput. Mater. 4 57
[61] Šabani D, Bacaksiz C, Milošević M V 2020 Phys. Rev. B 102 014457
[62] Zhang J 2023 Ph. D. Dissertation (Beijing: Institute of Physics, Chinese Academy of Sciences) (in Chinese) [张杰2023博士学位论文(北京: 中国科学院物理研究所)]
计量
- 文章访问数: 213
- PDF下载量: 11
- 被引次数: 0
下载:
