翟曉芳

翟曉芳教授是上海科技大學物質學院副教授、研究員、課題組長、博士生導師。

基本介紹

• 中文名：翟曉芳
• 學位/學歷：博士
• 專業方向：磁性量子材料和器件
• 職稱：教授

人物經歷

1997-2002 中國科學技術大學物理系，獲學士學位

2002-2008 美國伊利諾伊大學厄巴納-香檳分校（UIUC）物理系，獲博士學位

2008-2009 美國加州大學伯克利分校（UC-Berkeley）材料系，博士後

2010-2019 中國科學技術大學微尺度物質科學國家研究中心，副研究員

2020- 上海科技大學物質學院，副教授、研究員

研究方向

新型磁性量子材料和器件研究非常重要，不僅是發展自旋電子學器件的基礎，也是突破已有材料和器件功能壁壘的關鍵。我們主要通過雷射分子束外延，操縱單個原子層的堆疊“lego”結構，在單原子基礎上發展人工結構新材料，研究新型物理機制和結構作用下，包括（1）原子層級別界面效應；（2）二維單原子層；（3）電荷及自旋有序性等，磁性薄膜和器件的物性表現和深層原理，探索具有超小尺寸、超快回響等迫切需求的磁性量子材料和器件。

具體研究中，我們主要利用雷射分子束外延設備（圖1）和微納加工工藝，製備新型磁性薄膜和存儲記憶類器件。我們通過界面工程、應力調控、少層原子維度調控等手段，發展具有新型性能的磁性薄膜，例如多重磁易軸（例一）、高溫鐵磁絕緣性（例二）等，在此基礎上，製備基於新型磁性薄膜的記憶存儲類器件，主要包括磁隧道結（MTJ）、類腦突觸晶片、以及柔性器件等。

研究成果

1. 單原子層磁性薄膜由於不具備層間耦合，其磁性表現為和多層薄膜不同。我們製備了單原子層SrRuO3薄膜，將其封裝在SrTiO3保護層中，發現單原子層的SrRuO3薄膜仍然具有鐵磁性，但其各項異性發生了本質改變，表現為一種新型的8重對稱性（如下圖所示），即自旋方向在<111>軸的8個方向均能穩定保持，這是以往磁性多層膜和單晶中沒有被發現過的性質，預示了單層磁性薄膜可以被用於多態存儲。

2. 自然界中絕大多數鐵磁材料都是導體，反鐵磁材料都是絕緣體。反之，鐵磁絕緣體和反鐵磁導體都很難存在。這是由於鐵磁性需要電子具有一定的巡遊性，有利於不同晶格位置電子和電子之間的鐵磁性交換相互作用，而絕緣體的局域電子的磁性相互作用需要經過負離子（如O2-）的超交換相互作用。我們發現LaCoO3的薄膜在拉應力作用下，具有高達90K的鐵磁絕緣態（如下圖所示），而類似鐵磁絕緣體EuS的工作溫度僅為16K。這一不同尋常的高溫鐵磁絕緣態和Co原子的自旋態有序分布有關。

3.很多磁性材料都是小帶隙半導體，非常適合套用於半導體器件中。我們製備了小帶隙半導體Sr2IrO4和鐵電體BaTiO3的雙層薄膜，其中Sr2IrO4的小帶隙來自於自旋軌道耦合作用和庫倫相互作用，是一種非常新穎的反鐵磁材料。我們發現通過施加電場（如下圖所示），氧空位和電荷能夠在雙層膜之間來迴轉移，並且可重複性高達10000次以上。這一器件的穩定性遠超很多單層阻變薄膜的穩定性，這和雙層膜之間的能帶匹配有很大關係。在此基礎上，我們實現了類腦突觸的記憶和遺忘功能。

代表論文

Z. Cui, A. Grutter, H. Zhou, H. Cao, Y. Dong, D. Gilbert, J. Wang, Y.-S. Liu, J. Ma, Z. Hu, J. Guo, J. Xia, B. Kirby, P. Shafer, E. Arenholz, H. Chen*, X. Zhai*, Y. Lu. Correlation-Driven Eightfold Magnetic Anisotropy in a Two-Dimensional Oxide Monolayer, Sci. Adv. 6，eaay0114 (2020)

D. Meng#, H. Guo#, Z. Cui, C. Ma, J. Zhao, J. Lu, H. Xu, Z. Wang, X. Hu, Z. Fu, R. Peng, J. Guo, X. Zhai*, G. Brown, R, Knize, Y, Lu,* “Strain-induced high-temperature perovskite ferromagnetic insulator”, Proc. Natl. Acad. Sci. USA 115(12), 2873-2877 (2018).

X. Zhai*, L. Cheng, Y. Liu*, C. M. Schlepütz, S. Dong*, H. Li, X. Zhang, S. Chu, Li. Zheng, J. Zhang, A. Zhao, H. Hong, A. Bhattacharya, J. N. Eckstein, C. Zeng, “Correlating interfacial octahedral rotations with magnetism in (LaMnO3+δ)N/(SrTiO3)N superlattices”, Nat. Commun. 5, 4283 (2014).

X. Zhai, C. Mohapatra, A. B. Shah, J.G. Wen, A. Bhattacharya, J. M. Zuo, and J. N. Eckstein, “New optical absorption bands in atomic layer superlattices”, Adv. Mater. 22, 1136 (2010).

X. Zhai, A. J. Grutter, Y. Yun, Z. Cui, and Y. Lu, “Weak magnetism of Aurivillius-type multiferroic thin films probed by polarized neutron reflectivity”, Phys. Rev. Mater. 2, 044405 (2018).

J. Deng, B. Xia, X. Ma, H. Chen, H. Shan, X. Zhai, B. Li, A. Zhao*, Y. Xu*, W. Duan, S. Zhang, B. Wang*, J. G. Hou, Epitaxial growth of ultraflat stanene with topological band inversion, Nat. Mater. 17, 1081 (2018).

H. Xu, A. J. Grutter, Z. Cui, Z. Wang, X. Zhai*, Y. Lu*. The charge carrier transport with low temperature anomalies in engineered 4d/5d oxide superlattices of (Sr₂IrO₄)₄/(Sr₃Ru₂O₇)_N. Phys. Rev. B 101, 155151 (2020).

Q. Feng, D. Meng, H. Zhou, G. Liang, Z. Cui, H. Huang, J. Wang, J. Guo, C. Ma, X. Zhai*, Q. Lu*, and Y. Lu*, “Direct imaging revealing halved ferromagnetism in tensile-strained LaCoO₃ thin films”, Phys. Rev. Mater. 3, 074406 (2019).

H. Xu, X. Zhai*, Z. Wang, Z. Cui, Z. Fu, Y. Lu*, “An epitaxial synaptic device made by a band-offset BaTiO₃/Sr₂IrO₄ bilayer with high endurance and long retention”, Appl. Phys. Lett. 114, 102904 (2019).

C. Liu, F. An, P. Gharavi, et al. Large-scale multiferroic complex oxide epitaxy with magnetically switched polarization enabled by solution processing, Nat. Sci. Rev. 7, 84-91 (2020).

S. Zhu, D. Meng, G. Liang, G. Shi, P. Zhao, P. Cheng, Y. Li, X. Zhai, Y. Lu, L.Chen* and K. Wu*, Proximity-induced magnetism and an anomalous Hall effect in Bi2Se3/LaCoO3: a topological insulator/ferromagnetic insulator thin film heterostructure, Nanoscale 10, 10041-10049 (2018).

Z. Cui, X. Zhai, Yi-De Chuang, H. Xu, H. Huang, J. Wang, Z. Fu, R. Peng, J. Guo, and Y. Lu, “Resonant inelastic x-ray scattering study of Bi6Fe2Ti3O18, Bi6FeCoTi3O18, and LaBi5FeCoTi3O18 Aurivillius-phase oxides”, Phys. Rev. B 95, 205102 (2017).

D. Meng, X. Zhai*, C. Ma, H. Huang, Y. Yun, Y. Huang, Z. Fu, R. Peng, X. Mao, X. Chen, G. Brown, Y. Lu, “Self-modulated nanostructures in super-large-period Bi₁₁(Fe₅CoTi₃)_10/9O₃₃ epitaxial thin films”, Appl. Phys. Lett. 106, 212906 (2015).

Y. Yun, C. Ma. X. Zhai*, H. Huang, D. Meng, J. Wang, Z. Fu, R. Peng, G. J. Brown, and Y. Lu*, “Interface engineering in epitaxial growth of layered oxides via a conducting layer insertion” Appl. Phys. Lett. 107, 011602 (2015).

L. Li, H. Li, X. Zhai*, C. Zeng*, “Fabrication and Magnetic Properties of Single-Crystalline La0.33Pr0.34Ca0.33MnO3/MgO nanowires”, Appl. Phys. Lett. 103, 113101( 2013) (Sep.9th issue cover).

Y. Yun, X. Zhai*, C. Ma, H. Huang, D. Meng, Z. Cui, J. Wang, Z. Fu, R. Peng, Gail J. Brown and Y. Lu*, “Growth of single-crystalline Bi6FeCoTi3O18 thin films and their magnetic–ferroelectric properties”, Appl. Phys. Express 8, 054001 (2015).

X. Zhai*, C. Mohapatra, A. B. Shah, J.-M. Zuo, J. N. Eckstein, “Magnetic properties of atomic layer superlattices of (SrTiO3)N/(LaMnO3)N”, J. Appl. Phys. 113, 173913 (2013).

Z. Wang, X. Zhai*,Z. Fu, and Y. Lu, “Tuning LaAlO3 lattice structure by growth rate at the picometer scale in LaAlO3/SrTiO3 heterostructures”, J. Appl. Phys. 124, 125305 (2018).

X. Zhai*, Y. Yun, D. Meng, Z. Cui, H. Huang, J. Wang, Y. Lu,* “Research progress of multiferroicity in Bi-layered oxide single-crystalline thin films”, Acta. Phys. Sin. 67, 157702 (2018).

H. Cao, Y. Liu, G. Liang, A. Zhao, X. Zhai*, “Unraveling interfacial strain and interfacial lattice reconstruction mechanism of ultrathin LaMnO3+δ layers in LaMnO3+δ/SrTiO3 superlattices”, J. Appl. Phys. 122, 085309 (2017).

J. N. Eckstein, M. Zheng, X. Zhai, B. Davidson, M. Warusawithana, S. Oh, “Atomic layer-by-layer molecular beam epitaxy of complex oxide films and heterostructures”, Chap. 21, Molecular beam epitaxy : from research to mass production, edited by Mohamed Henini, Elsevier (2013)

C. He, A. Grutter, M. Gu, N. D. Browning, Y. Takamura, B. J. Kirby, J. A. Borchers, J. W. Kim, M. R. Fitzsimmons, X. Zhai, V. V. Mehta, F. J. Wong, and Y. Suzuki, “Interfacial ferromagnetism and exchange bias in CaRuO₃/CaMnO₃ superlattices”,Phys. Rev. Lett.109, 197202 (2012).

H. Zhang, J.-H. Choi, Y. Xu, X. Wang, X. Zhai, B. Wang, C. Zeng, J.-H. Cho, Z. Zhang, and J. G. Hou, “Atomic structure, energetics, and dynamics of topological solitons in Indium chains on Si(111) surfaces”, Phys. Rev. Lett. 106, 026801 (2011).

Z. Li, P. Wu, C. Wang, X. Fan, W. Zhang, X. Zhai, C. Zeng, Z. Li, J. Yang, and J. G. Hou, “Low-temperature growth of graphene by chemical vapor deposition using solid and liquid carbon sources”, ACS Nano 5, 3385 (2011)

A. Shah, Q. Ramasse, X. Zhai, J. G. Wen, S. J. May, I.Petrov, A. Bhattacharya, P. Abbamonte, J. N. Eckstein, J.-M. Zuo, “Probing interfacial electronic structures in atomic layer LaMnO₃ and SrTiO₃ superlattices”, Adv. Mater.22, 1156 (2010).

S. J. May, P. J. Ryan, J. L. Robertson, J.-W. Kim, T. S. Santos, E. Karapetrova, J. L. Zarestky, X. Zhai, S. G. E. te Velthuis, J. N. Eckstein, S. D. Bader, A. Bhattacharya, “Enhanced ordering temperatures in antiferromagnetic manganite superlattices”, Nat. Mater. 8, 892 (2009).

A. Bhattacharya, S. May, S. Velthuis, M. Warusawithana, X. Zhai, B. Jiang, J. M. Zuo, M. Fitzimmons, S. D. Bader, and J. N. Eckstein, “Metal-insulator transition and its relation to magnetic structure in (LaMnO₃)_2n/(SrMnO₃)_n superlattices”, Phys. Rev. Lett. 100, 257203 (2008).

H. B. Zhao, K. J. Smith, Y. Fan, G. Lupke, A. Bhattacharya, S. D. Bader, M.Warusawithana, X. Zhai, J. N. Eckstein, “Viscous spin exchange torque on precessional magnetization in (LaMnO₃)_2n/(SrMnO₃)n superlattices”, Phys. Rev. Lett. 100, 117208 (2008).

S. Smadici, P. Abbamonte, A. Bhattacharya, X. Zhai, B. Jiang, A. Rusydi, J. N. Eckstein, S. D. Bader, and J. M. Zuo, “Electronic reconstruction at SrMnO₃-LaMnO₃ superlattice interfaces”, Phys. Rev. Lett. 99, 196404 (2007).