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磁电耦合效应是百年铁电领域中新兴的科学话题和前沿难点. 包含两种及以上铁性序的多铁性材料则是追求本征强磁电耦合的理想体系, 其展现了丰富的物理性质, 蕴含着很高的应用潜力. 作为关联电子大家庭的一个分支, 多铁性材料体系也涉及电荷、自旋、轨道, 以及晶格多重自由度. 但过往的磁电耦合研究对自旋与晶格自由度关注最多, 却往往忽略了其中的电荷自由度. 实际上, 电荷自由度可以在磁电耦合中扮演重要的媒介作用. 本文将介绍异质结中的铁电场效应和单相多铁性材料中的电荷序所涉及的磁电耦合物理机制, 以及回顾作者近年来在此方向上的若干尝试, 希望能为本领域的研究者提供一些参考.Magnetoelectricity is an emerging topic and a frontier issue of the field of ferroelectricity. Multiferroics containing more than one ferroic order is an ideal system to pursuit intrinsic and robust magnetoelectric coupling, which holds rich physics and great potential applications. As a branch of the correlated electron family, multiferroic also has multiple degrees of freedom, including the charge, spin, orbital, and lattice. Among them, the charge degree of freedom has been mostly overlooked in the past researches and actually it may play an important role in magnetoelectricity. In this topical review, the charge-mediated magnetoelectricity is introduced, including the ferroelectric field effect in heterostructures and the charge ordering in single-phase multiferroics. The physical mechanisms will be revealed, together with several examples we given in recent years. We hope that this topical review can provide a reference for the researches in this vigorous filed.
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Keywords:
- multiferroic /
- magnetoelectricity /
- field effect /
- charge ordering
[1] Hill N A 2000 J. Phys. Chem. B 104 6694Google Scholar
[2] Wang J, Neaton J B, Zheng H, et al. 2003 Science 299 1719Google Scholar
[3] Kimura T, Goto T, Shintani H, Ishizaka K, Arima T, Tokura Y 2003 Nature 426 55Google Scholar
[4] Dong S, Liu J M, Cheong S W, Ren Z F 2015 Adv. Phys. 64 519Google Scholar
[5] Ramesh R, Spaldin N A 2007 Nat. Mater. 6 21Google Scholar
[6] Dong S, Xiang H J, Dagotto E 2019 Natl. Sci. Rev. 6 629Google Scholar
[7] 徐萌, 晏建民, 徐志学, 郭磊, 郑仁奎, 李晓光 2018 物理学报 67 157506Google Scholar
Xu M, Yan J M, Xu Z X, Guo L, Zheng R K, Li X G 2018 Acta. Phys. Sin. 67 157506Google Scholar
[8] 宋骁, 高兴森, 刘俊明 2018 物理学报 67 157512Google Scholar
Song X, Gao X S, Liu J M 2018 Acta Phys. Sin. 67 157512Google Scholar
[9] 胡婷, 阚二军 2018 物理学报 67 157701Google Scholar
Hu T, Kan E J 2018 Acta Phys. Sin. 67 157701Google Scholar
[10] Spaldin N A, Ramesh R 2019 Nat. Mater. 18 203Google Scholar
[11] Dong S, Dagotto E 2013 Phys. Rev. B 88 140404(R)Google Scholar
[12] Duan C G, Jaswal S S, Tsymbal E Y 2006 Phys. Rev. Lett. 97 047201Google Scholar
[13] Duan C G, Velev J P, Sabirianov R F, Zhu Z Q, Chu J H, Jaswal S S, Tsymbal E Y 2008 Phys. Rev. Lett. 101 137201Google Scholar
[14] Rondinelli J M, Stengel M, Spaldin N A 2008 Nat. Nano. 3 46Google Scholar
[15] Yang P, Zhu J S, Lee J Y, Lee H Y 2011 Trans. Nonferrous Met. Soc. China 21 s92Google Scholar
[16] Radaelli G, Petti D, Plekhanov E, Fina I, Torelli P, Salles B R, Cantoni M, Rinaldi C, Gutiérrez D, Panaccione G, Varela M, Picozzi S, Fontcuberta J, Bertacco R 2014 Nat. Commun. 5 3404Google Scholar
[17] Chen H H, Ismail-Beigi S 2012 Phys. Rev. B 86 024433Google Scholar
[18] Vaz C A F, Walker F J, Ahn C H, Ismail-Beigi S 2015 J. Phys.: Condens. Matter 27 123001Google Scholar
[19] Burton J D, Tsymbal E Y 2009 Phys. Rev. B 80 174406Google Scholar
[20] Molegraaf H J A, Hoffman J, Vaz C A F, Gariglio S, Marel D V D, Ahn C H, Triscone J M 2009 Adv. Mater. 21 3470Google Scholar
[21] Vaz C A F, Hoffman J, Segal Y, Reiner J W, Grober R D, Zhang Z, Ahn C H, Walker F J 2010 Phys. Rev. Lett. 104 127202Google Scholar
[22] Vaz C A F, Hoffman J, Segal Y, Marshall M S J, Reiner J W, Zhang Z, Grober R D, Walker F J, Ahn C H 2011 J. Appl. Phys. 109 07D905Google Scholar
[23] Lu H, George T A, Wang Y, Ketsman I, Burton J D, Bark C W, Ryu S, Kim D J, Wang J, Binek C, Dowben P A, Sokolov A, Eom C B, Tsymbal E Y, Gruverman A 2012 Appl. Phys. Lett. 100 232904Google Scholar
[24] Jiang L, Choi W S, Jeen H, Egami T, Lee H N 2012 Appl. Phys. Lett. 101 042902Google Scholar
[25] Yi D, Liu J, Okamoto S, Jagannatha S, Chen Y C, Yu P, Chu Y H, Arenholz E, Ramesh R 2013 Phys. Rev. Lett. 111 127601Google Scholar
[26] Dong S, Zhang X T, Yu R, Liu J M, Dagotto E 2011 Phys. Rev. B 84 155117Google Scholar
[27] Ma X, Kumar A, Dussan S, Zhai H, Fang F, Zhao H B, Scott J F, Katiyar R S, Lüpke G 2014 Appl. Phys. Lett. 104 132905Google Scholar
[28] Weng Y K, Lin L F, Dagotto E, Dong S 2016 Phys. Rev. Lett. 117 037601Google Scholar
[29] Bhattacharya A, May S J, Velthuis S G E, Warusawithana M, Zhai X, Jiang B, Zuo J M, Fitzsimmons M R, Bader S D, Eckstein J N 2008 Phys. Rev. Lett. 100 257203Google Scholar
[30] Dong S, Yu R, Yunoki S, Alvarez G, Liu J M, Dagotto E 2008 Phys. Rev. B 78 201102(R)Google Scholar
[31] Gibert M, Zubko P, Scherwitzl R, Íñiguez J, Triscone J M 2012 Nature Mater. 11 195Google Scholar
[32] Brink J V D, Khomskii D I 2008 J. Phys.: Condens. Matter 20 434217Google Scholar
[33] Ikeda N, Ohsumi H, Ohwada K, Ishii K, Inami T, Kakurai K, Murakami Y, Yoshii K, Mori S, Horibe Y, Kitô H 2005 Nature 436 1136Google Scholar
[34] Nagano A, Naka M, Nasu J, Ishihara S 2007 Phys. Rev. Lett. 99 217202Google Scholar
[35] Alexe M, Ziese M, Hesse D, Esquinazi P, Yamauchi K, Fukushima T, Picozzi S, Gösel U 2009 Adv. Mater. 21 4452Google Scholar
[36] Efremov D V, van den Brink J, Khomskii D I 2004 Nat. Mater. 3 853Google Scholar
[37] Giovannetti G, Kumar S, van den Brink J, Picozzi S 2009 Phys. Rev. Lett. 103 037601Google Scholar
[38] Portier J, Tressaud A, De Pape R, Hagenmuller P 1970 J. Solid State Chem. 2 269Google Scholar
[39] Lin L F, Xu Q R, Zhang Y, Zhang J J, Liang Y P, Dong S 2017 Phys. Rev. Mater. 1 071401(R)Google Scholar
[40] Wu S W, Cybart S A, Yu P, Rossell M D, Zhang J X, Ramesh R, Dynes R C 2010 Nat. Mater. 9 756Google Scholar
[41] Yu P, Lee J S, Okamoto S, Rossell M D, Huijben M, Yang C H, He Q, Zhang J X, Yang S Y, Lee M J, Ramasse Q M, Erni R, Chu Y H, Arena D A, Kao C C, Martin L, Ramesh R 2010 Phys. Rev. Lett. 105 027201Google Scholar
[42] Weisheit M, Fähler S, Marty A, Souche Y, Poinsignon C, Givord D 2007 Science 315 349Google Scholar
[43] Eerenstein W, Wiora M, Prieto J L, Scott J F, Mathur N D 2007 Nat. Mater. 6 348Google Scholar
[44] Lebeugle D, Mougin A, Viret M, Colson D, Ranno L 2009 Phys. Rev. Lett. 103 257601Google Scholar
[45] Tsymbal E Y, Kohlstedt H 2006 Science 313 181Google Scholar
[46] Garcia V, Bibes M 2014 Nat. Commun. 5 4289Google Scholar
[47] Chen A, Wen Y, Fang B, Zhao Y L, Zhang Q, Chang Y S, Li P S, Wu H, Huang H L, Lu Y L, Zeng Z M, Cai J W, Han X F, Wu T, Zhang X X, Zhao Y G 2019 Nat. Commun. 10 243Google Scholar
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图 1 铁电场效应示意图(箭头表示铁电极化的方向) (a) 极化向上时, 界面处吸引空穴; (b) 极化向下时, 界面处吸引电子; 即极化翻转导致界面处局域电荷重新分布[11]
Fig. 1. Sketch of ferroelectric-field effect: (a) When the ferroelectric polarization (as denoted by assows) is upward, holes are attracted at the interface; (b) in contrast, electrons will gather at the interface when the polarization is reversed [11].
图 2 (a) La1–xAxMnO3/BaTiO3 (001)异质结结构示意图, 界面处La1–xAxMnO3 (LAMO)(虚线框区域)随着BaTiO3 (BTO)极化方向(黑色箭头所示)翻转, 从铁磁态转变为A型反铁磁态; (b) 界面处锰氧化物的局域态密度随着BaTiO3极化方向翻转而变化(极化指向界面时, 蓝色虚线表示; 极化背离界面时, 红色实线)[19]
Fig. 2. (a) Interfacial magnetic transition induced by charge redistribution at the La1–xAxMnO3/BaTiO3 interface. Specifically, the local moments of Mn (denoted by small arrows) close to the interface change from parallel to antiparallel as the polarization of BaTiO3 (denoted by large arrows) is reversed; (b) the spin-resolved local density of states of the interfacial La0.5A0.5MnO3 varies with the ferroelectric field direction of BaTiO3, shifting downwards (blue dashed line) or upwards (red solid line) as the polarization pointing to or away from the interface, respectively[19].
图 3 (a) 100 K时PbZr0.2Ti0.8O3不同极化方向下La0.8Sr0.2MnO3在面内[100]方向上测得的磁滞回线; (b)异质结界面处受极化翻转调制的自旋结构示意图(黑色箭头, Mn离子自旋方向; n, 界面开始的Mn离子层数[20]); (c) 100 K时受外电场调控的磁响应曲线[21]; (d) BiFeO3/La0.5Ca0.5MnO3界面电荷密度及自旋结构示意图[25]
Fig. 3. (a) Magnetic hysteresis curves of La0.8Sr0.2MnO3 along [100] direction taken at 100 K as the PbZr0.2Ti0.8O3 polariztion points down into (black dots) or away from (red hollow diamonds) the interface; (b) sketch of the spin configurations of interfacial Mn for the two polarization states of PbZr0.2Ti0.8O3. The schematic change of Mn and O orbital states are shown along with the layer-resolved magnetic moment. The spin orientation of Mn are denoted by arrows[20]; (c) magnetoelectric hysteresis curve taken at 100 K which is obviously manipulated by the external electric field[21]; (d) sketch of the interfacial charge distribution and spin structure of BiFeO3/La0.5Ca0.5MnO3 (denoed by arrows with different size)[25].
图 4 (a)铁电-锰氧化物异质结模型模拟结果: 铁电极化(灰色区域)调节界面处静电势(线)和Mn上eg电子密度分布(点线); (b)铁电调控磁性相图: 从铁磁基态出发, 加大铁电极化(Q, 负值代表极化方向背离界面), 可以诱发界面反铁磁相(如CE1, Cx1)[26]
Fig. 4. (a) Schematic of the interfacial electrostatic potential (lines without dots) and the corresponding curve of Mns’ eg charge density (line with dots), with the original density (dashed lines) for reference. The typical polarization cases (left: Q = –0.4, right: Q = 0.4) are shown for better illustration. The sandwiched ferroelectric gate and its polarization are also drafted. (b) Ferroelectric field dependent ground-state phase diagram for the interfacial layers. In addition to the intrinsic ferromangentic phase, there are many antiferromagnetic orders (such as CE1 and Cx1)[26].
图 5 (a) 锰氧化物-铁电BaTiO3超晶格结构示意图(黄色小球代表三价稀土金属元素和二价碱土金属元素的混合; Ba, Mn, Ti, O分别用绿色、紫色、蓝绿色和红色表示; +P和–P箭头代表铁电极化方向; 绿色箭头代表(铁磁相)自旋; 紫色箭头代表(亚铁磁相)自旋); (b) 不同MnO2层中Mn的eg电荷密度(用紫色球体大小区分)以及相应静电势(黑色横线)示意图[11]
Fig. 5. (a) The superlattice structure composed of manganite and ferroelectric titanate. The Ba, O, Ti, Mn, and the mixture of trivalent and divalent cations are denoted by green, red, cyan, purple, and yellow balls. The n/p-type interfaces have been marked. The magnetic order of manganite can be switched from ferromagnetic to ferrimagnetic as the polarization of titanate changes from –P (left) to +P (right); (b) the layer-resolved eg density (spheres) and electrostatic potential (bars) modulated by n/p-type interfaces (bricks) and –P/+P polarizations (arrows)[11].
图 6 (a), (b)沿不同方向观察的立方结构中G型反铁磁序示意图, 其中绿色和红色分别代表不同自旋方向; (c)沿[111]方向构建的BiFeO3/SrTiO3超晶格结构示意图; (d), (e)超晶格中BiFeO3层中电子密度空间分布示意图, 箭头分别表示极化P的方向(绿色)和净磁矩M的方向(橘色); (f)电控磁示意图: 随着极化方向的翻转, 体系净磁矩方向也相应发生翻转[28]
Fig. 6. (a), (b) Schematic of G-type antiferromagnetic order in pseudocubic perovskite structure (as in BiFeO3) viewed from different orientations. The antiparallel spins are distinguished by green and purple; (c) the superlattice structure of BiFeO3/SrTiO3 stacking along the pseudocubic [111] direction. The two Fe’s in bilayer are labeled as 1 and 2; (d), (e) spatial charge distribution for the Pup and Pdown cases. The orientations of M and P are also indicated; (f) the schematic process of the electric field switch of magnetism, forming an E-M hysteresis loop[28].
图 7 (a)三金红石LiFe2F6的晶体结构(棕色球, Fe; 绿色球, Li; 银色球, F); (b), (c)在面内双轴应力(–3%)作用下LiFe2F6中以电荷序为媒介的磁电耦合示意图: (b) 模拟的材料铁电极化翻转过程示意图, 插图为初态、中间态和末态时Fe2+/Fe3+二聚体的示意图; (c)随铁电极化变化的净磁矩翻转过程示意图, 插图为初末态对应的价带顶部分电荷密度图(沿[110]方向)[39]
Fig. 7. (a) Crystal structure of LiFe2F6, in which the Fe, Li, and F are denoted by brown, green, and silver balls, respectively; (b), (c) the sketch of charge-ordering-mediated magnetoelectricity in LiFe2F6 with moderate compressive strain: (b) the switch of polarization. Insert: sketch of the charge redistribution within Fe2+/Fe3+ dimer; (c) the switch of local moment. Insert: the corresponding profile of partial charge density[39].
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[1] Hill N A 2000 J. Phys. Chem. B 104 6694Google Scholar
[2] Wang J, Neaton J B, Zheng H, et al. 2003 Science 299 1719Google Scholar
[3] Kimura T, Goto T, Shintani H, Ishizaka K, Arima T, Tokura Y 2003 Nature 426 55Google Scholar
[4] Dong S, Liu J M, Cheong S W, Ren Z F 2015 Adv. Phys. 64 519Google Scholar
[5] Ramesh R, Spaldin N A 2007 Nat. Mater. 6 21Google Scholar
[6] Dong S, Xiang H J, Dagotto E 2019 Natl. Sci. Rev. 6 629Google Scholar
[7] 徐萌, 晏建民, 徐志学, 郭磊, 郑仁奎, 李晓光 2018 物理学报 67 157506Google Scholar
Xu M, Yan J M, Xu Z X, Guo L, Zheng R K, Li X G 2018 Acta. Phys. Sin. 67 157506Google Scholar
[8] 宋骁, 高兴森, 刘俊明 2018 物理学报 67 157512Google Scholar
Song X, Gao X S, Liu J M 2018 Acta Phys. Sin. 67 157512Google Scholar
[9] 胡婷, 阚二军 2018 物理学报 67 157701Google Scholar
Hu T, Kan E J 2018 Acta Phys. Sin. 67 157701Google Scholar
[10] Spaldin N A, Ramesh R 2019 Nat. Mater. 18 203Google Scholar
[11] Dong S, Dagotto E 2013 Phys. Rev. B 88 140404(R)Google Scholar
[12] Duan C G, Jaswal S S, Tsymbal E Y 2006 Phys. Rev. Lett. 97 047201Google Scholar
[13] Duan C G, Velev J P, Sabirianov R F, Zhu Z Q, Chu J H, Jaswal S S, Tsymbal E Y 2008 Phys. Rev. Lett. 101 137201Google Scholar
[14] Rondinelli J M, Stengel M, Spaldin N A 2008 Nat. Nano. 3 46Google Scholar
[15] Yang P, Zhu J S, Lee J Y, Lee H Y 2011 Trans. Nonferrous Met. Soc. China 21 s92Google Scholar
[16] Radaelli G, Petti D, Plekhanov E, Fina I, Torelli P, Salles B R, Cantoni M, Rinaldi C, Gutiérrez D, Panaccione G, Varela M, Picozzi S, Fontcuberta J, Bertacco R 2014 Nat. Commun. 5 3404Google Scholar
[17] Chen H H, Ismail-Beigi S 2012 Phys. Rev. B 86 024433Google Scholar
[18] Vaz C A F, Walker F J, Ahn C H, Ismail-Beigi S 2015 J. Phys.: Condens. Matter 27 123001Google Scholar
[19] Burton J D, Tsymbal E Y 2009 Phys. Rev. B 80 174406Google Scholar
[20] Molegraaf H J A, Hoffman J, Vaz C A F, Gariglio S, Marel D V D, Ahn C H, Triscone J M 2009 Adv. Mater. 21 3470Google Scholar
[21] Vaz C A F, Hoffman J, Segal Y, Reiner J W, Grober R D, Zhang Z, Ahn C H, Walker F J 2010 Phys. Rev. Lett. 104 127202Google Scholar
[22] Vaz C A F, Hoffman J, Segal Y, Marshall M S J, Reiner J W, Zhang Z, Grober R D, Walker F J, Ahn C H 2011 J. Appl. Phys. 109 07D905Google Scholar
[23] Lu H, George T A, Wang Y, Ketsman I, Burton J D, Bark C W, Ryu S, Kim D J, Wang J, Binek C, Dowben P A, Sokolov A, Eom C B, Tsymbal E Y, Gruverman A 2012 Appl. Phys. Lett. 100 232904Google Scholar
[24] Jiang L, Choi W S, Jeen H, Egami T, Lee H N 2012 Appl. Phys. Lett. 101 042902Google Scholar
[25] Yi D, Liu J, Okamoto S, Jagannatha S, Chen Y C, Yu P, Chu Y H, Arenholz E, Ramesh R 2013 Phys. Rev. Lett. 111 127601Google Scholar
[26] Dong S, Zhang X T, Yu R, Liu J M, Dagotto E 2011 Phys. Rev. B 84 155117Google Scholar
[27] Ma X, Kumar A, Dussan S, Zhai H, Fang F, Zhao H B, Scott J F, Katiyar R S, Lüpke G 2014 Appl. Phys. Lett. 104 132905Google Scholar
[28] Weng Y K, Lin L F, Dagotto E, Dong S 2016 Phys. Rev. Lett. 117 037601Google Scholar
[29] Bhattacharya A, May S J, Velthuis S G E, Warusawithana M, Zhai X, Jiang B, Zuo J M, Fitzsimmons M R, Bader S D, Eckstein J N 2008 Phys. Rev. Lett. 100 257203Google Scholar
[30] Dong S, Yu R, Yunoki S, Alvarez G, Liu J M, Dagotto E 2008 Phys. Rev. B 78 201102(R)Google Scholar
[31] Gibert M, Zubko P, Scherwitzl R, Íñiguez J, Triscone J M 2012 Nature Mater. 11 195Google Scholar
[32] Brink J V D, Khomskii D I 2008 J. Phys.: Condens. Matter 20 434217Google Scholar
[33] Ikeda N, Ohsumi H, Ohwada K, Ishii K, Inami T, Kakurai K, Murakami Y, Yoshii K, Mori S, Horibe Y, Kitô H 2005 Nature 436 1136Google Scholar
[34] Nagano A, Naka M, Nasu J, Ishihara S 2007 Phys. Rev. Lett. 99 217202Google Scholar
[35] Alexe M, Ziese M, Hesse D, Esquinazi P, Yamauchi K, Fukushima T, Picozzi S, Gösel U 2009 Adv. Mater. 21 4452Google Scholar
[36] Efremov D V, van den Brink J, Khomskii D I 2004 Nat. Mater. 3 853Google Scholar
[37] Giovannetti G, Kumar S, van den Brink J, Picozzi S 2009 Phys. Rev. Lett. 103 037601Google Scholar
[38] Portier J, Tressaud A, De Pape R, Hagenmuller P 1970 J. Solid State Chem. 2 269Google Scholar
[39] Lin L F, Xu Q R, Zhang Y, Zhang J J, Liang Y P, Dong S 2017 Phys. Rev. Mater. 1 071401(R)Google Scholar
[40] Wu S W, Cybart S A, Yu P, Rossell M D, Zhang J X, Ramesh R, Dynes R C 2010 Nat. Mater. 9 756Google Scholar
[41] Yu P, Lee J S, Okamoto S, Rossell M D, Huijben M, Yang C H, He Q, Zhang J X, Yang S Y, Lee M J, Ramasse Q M, Erni R, Chu Y H, Arena D A, Kao C C, Martin L, Ramesh R 2010 Phys. Rev. Lett. 105 027201Google Scholar
[42] Weisheit M, Fähler S, Marty A, Souche Y, Poinsignon C, Givord D 2007 Science 315 349Google Scholar
[43] Eerenstein W, Wiora M, Prieto J L, Scott J F, Mathur N D 2007 Nat. Mater. 6 348Google Scholar
[44] Lebeugle D, Mougin A, Viret M, Colson D, Ranno L 2009 Phys. Rev. Lett. 103 257601Google Scholar
[45] Tsymbal E Y, Kohlstedt H 2006 Science 313 181Google Scholar
[46] Garcia V, Bibes M 2014 Nat. Commun. 5 4289Google Scholar
[47] Chen A, Wen Y, Fang B, Zhao Y L, Zhang Q, Chang Y S, Li P S, Wu H, Huang H L, Lu Y L, Zeng Z M, Cai J W, Han X F, Wu T, Zhang X X, Zhao Y G 2019 Nat. Commun. 10 243Google Scholar
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