Mn(Sb/Bi)2nTe3n+1的单晶制备及磁性研究

本征磁性二维材料MnSb_2nTe_3n+1体系因其磁性和拓扑表面态结合的特点吸引了广泛的研究。目前该体系的研究集中在以非磁性层插入构建异质结为主的磁性调控上，但对Mn晶格占位的磁性调控还没有进行深入的探究。本文选取MnSb_2nTe_3n+1体系中的MnSb₂Te₄和MnSb₄Te₇为研究对象，通过自助熔剂法控制单晶生长热力学参数和设计化学元素组分，改变单晶内Mn占位（原Mn位置Mn含量、Mn-Sb及Mn-Bi反位缺陷浓度）来实现单晶磁性的精准调控，最终确立了单晶生长工艺-结构-磁性的构效关系。

首先，改变退火温度和冷速可以显著调控MnSb₂Te₄的磁性。升高退火温度可以获得具有更高居里温度的亚铁磁性单晶。在高退火温度635℃下减缓单晶生长冷速，获得的单晶居里温度高达37.5K，为目前该工艺获得的最高值。进一步磁性研究表明，MnSb₂Te₄层内反铁磁相互作用得到增强。基于分子场理论构建的MnSb₂Te₄模型，发现磁性的增强主要来源于较慢的单晶生长冷速增加原Mn位置Mn含量。

此外，我们克服了MnSb₄Te₇的生长困难，摸索出了易生长、高产率的单晶制备路线。和MnSb₂Te₄相比，MnSb₄Te₇因存在非磁性层且生长温度低，使得Mn晶格位点多且含量低，导致热力学参数调控Mn无序分布难以实现类似效果。实验表明，Bi掺杂可以增大MnSb₄Te₇中Mn的无序度，从而诱导单晶从反铁磁至亚铁磁构型转变。结合交流磁化率结果，MnSb₂Te₄和MnSb₄Te₇中Mn无序分布都将引入与磁畴有关的磁弛豫现象。本文研究结果丰富了二维磁性材料的磁性调控方法和磁态研究，为二维磁性材料的发展和高温量子反常霍尔效应的观测提供了重要信息。

[1] MOORE G E. Cramming more components onto integrated circuits [Z]. McGraw-Hill New York. 1965

[2] DOKMANIĆ I, KOLUNDŽIJA M, VETTERLI M. Beyond Moore-Penrose: Sparse pseudoinverse; proceedings of the 2013 IEEE International Conference on Acoustics, Speech and Signal Processing, F, 2013 [C]. IEEE. International Conference on Robotics and Automation (ICRA), 2013: 6526-6530.

[3] ARDEN W, BRILLOUëT M, COGEZ P, et al. More-than-Moore white paper [J]. Version, 2010, 2: 14.

[4] WANG Z, TANG C, SACHS R, et al. Proximity-Induced ferromagnetism in graphene revealed by the anomalous Hall effect [J]. Physical Review Letters, 2015, 114(1): 016603.

[5] YAZYEV O V, HELM L. Defect-Induced magnetism in graphene [J]. Physical Review B, 2007, 75(12): 125408.

[6] CAO T, LI Z, LOUIE S G. Tunable magnetism and half-metallicity in hole-doped monolayer GaSe [J]. Physical Review Letters, 2015, 114(23): 236602.

[7] CASTRO E V, PERES N M R, STAUBER T, et al. Low-Density ferromagnetism in biased bilayer graphene [J]. Physical Review Letters, 2008, 100(18): 186803.

[8] HUANG B, CLARK G, KLEIN D R, et al. Electrical control of 2D magnetism in bilayer CrI3 [J]. Nature Nanotechnology, 2018, 13(7): 544-548.

[9] GONG C, LI L, LI Z, et al. Discovery of intrinsic ferromagnetism in two-dimensional van der Waals crystals [J]. Nature, 2017, 546(7657): 265-269.

[10] WANG H, XU R, LIU C, et al. Pressure-Dependent intermediate magnetic phase in thin Fe3GeTe2 flakes [J]. The Journal of Physical Chemistry Letters, 2020, 11(17): 7313-7319.

[11] BONILLA M, KOLEKAR S, MA Y, et al. Strong room-temperature ferromagnetism in VSe2 monolayers on van der Waals substrates [J]. Nature Nanotechnology, 2018, 13(4): 289-293.

[12] OHARA D J, ZHU T, TROUT A H, et al. Room temperature intrinsic ferromagnetism in epitaxial manganese selenide films in the monolayer limit [J]. Nano Letters, 2018, 18(5): 3125-3131.

[13] OTROKOV M M, KLIMOVSKIKH I I, BENTMANN H, et al. Prediction and observation of an antiferromagnetic topological insulator [J]. Nature, 2019, 576(7787): 416-422.

[14] ZHANG X, ZHANG S, JIANG Z, et al. Tunable intrinsic ferromagnetic topological phases in bulk van der Waals crystal MnSb6Te10 [J]. arXiv preprint arXiv:211104973, 2021.

[15] LIU Y, WANG L-L, ZHENG Q, et al. Site mixing for engineering magnetic topological insulators [J]. Physical Review X, 2021, 11(2): 021033.

[16] ZHANG S, XU R, LUO N, et al. Two-Dimensional magnetic materials: structures, properties and external controls [J]. Nanoscale, 2021, 13(3): 1398-1424.

[17] XIAO H, MI M-J, WANG Y-L. Recent development in two-dimensional magnetic materials and multi-field control of magnetism [J]. ACTA PHYSICA SINICA, 2021, 70(12).

[18] MCGUIRE M A. Crystal and magnetic structures in layered, transition metal dihalides and trihalides [J]. Crystals, 2017, 7(5): 121.

[19] KIM H H, YANG B, LI S, et al. Evolution of interlayer and intralayer magnetism in three atomically thin chromium trihalides [J]. Proceedings of the National Academy of Sciences, 2019, 116(23): 11131-11136.

[20] ZHONG D, SEYLER K L, LINPENG X, et al. Layer-Resolved magnetic proximity effect in van der Waals heterostructures [J]. Nature Nanotechnology, 2020, 15(3): 187-191.

[21] MCGUIRE M A, DIXIT H, COOPER V R, et al. Coupling of crystal structure and magnetism in the layered, ferromagnetic insulator CrI3 [J]. Chemistry of Materials, 2015, 27(2): 612-620.

[22] BEDOYA-PINTO A, JI J-R, PANDEYA A K, et al. Intrinsic 2D-XY ferromagnetism in a van der Waals monolayer [J]. Science, 2021, 374(6567): 616-620.

[23] KANG L, YE C, ZHAO X, et al. Phase-Controllable growth of ultrathin 2D magnetic FeTe crystals [J]. Nature Communications, 2020, 11(1): 3729.

[24] COAK M J, JARVIS D M, HAMIDOV H, et al. Tuning dimensionality in van der Waals antiferromagnetic Mott insulators TMPS3 [J]. Journal of Physics: Condensed Matter, 2019, 32(12): 124003.

[25] LEE J-U, LEE S, RYOO J H, et al. Ising-Type Magnetic Ordering in atomically thin FePS3 [J]. Nano Letters, 2016, 16(12): 7433-7438.

[26] LANçON D, WALKER H C, RESSOUCHE E, et al. Magnetic structure and magnon dynamics of the quasi two-dimensional antiferromagnet FePS3 [J]. Physical Review B, 2016, 94(21): 214407.

[27] KIM K, LIM S Y, LEE J-U, et al. Suppression of magnetic ordering in XXZ-type antiferromagnetic monolayer NiPS3 [J]. Nature Communications, 2019, 10(1): 345.

[28] KANG S, KIM K, KIM B H, et al. Coherent many-body exciton in van der Waals antiferromagnet NiPS3 [J]. Nature, 2020, 583(7818): 785-789.

[29] LI Y F, WANG W, GUO W, et al. Electronic structure of ferromagnetic semiconductor CrGeTe3 by angle-resolved photoemission spectroscopy [J]. Physical Review B, 2018, 98(12): 125127.

[30] ITO N, KIKKAWA T, BARKER J. Spin Seebeck effect in the layered ferromagnetic insulators CrSiTe3 and CrGeTe3 [J]. Physical Review B, 2019, 100(6): 060402.

[31] DENG Y, YU Y, SONG Y, et al. Gate-Tunable room-temperature ferromagnetism in two-dimensional Fe3GeTe2 [J]. Nature, 2018, 563(7729): 94-99.

[32] MAY A F, OVCHINNIKOV D, ZHENG Q, et al. Ferromagnetism near room temperature in the cleavable van der Waals crystal Fe5GeTe2 [J]. ACS Nano, 2019, 13(4): 4436-4442.

[33] WANG Z, ZHANG T, DING M, et al. Electric-Field control of magnetism in a few-layered van der Waals ferromagnetic semiconductor [J]. Nature Nanotechnology, 2018, 13(7): 554-559.

[34] JIANG S, LI L, WANG Z, et al. Controlling magnetism in 2D CrI3 by electrostatic doping [J]. Nature Nanotechnology, 2018, 13(7): 549-553.

[35] LI T, JIANG S, SIVADAS N, et al. Pressure-Controlled interlayer magnetism in atomically thin CrI3 [J]. Nature Materials, 2019, 18(12): 1303-1308.

[36] SONG T, FEI Z, YANKOWITZ M, et al. Switching 2D magnetic states via pressure tuning of layer stacking [J]. Nature Materials, 2019, 18(12): 1298-1302.

[37] LIN Z, LOHMANN M, ALI Z A, et al. Pressure-Induced spin reorientation transition in layered ferromagnetic insulator Cr2Ge2Te6 [J]. Physical Review Materials, 2018, 2(5): 051004.

[38] FEI Z, HUANG B, MALINOWSKI P, et al. Two-Dimensional itinerant ferromagnetism in atomically thin Fe3GeTe2 [J]. Nature Materials, 2018, 17(9): 778-782.

[39] HUANG C, FENG J, WU F, et al. Toward intrinsic room-temperature ferromagnetism in two-dimensional semiconductors [J]. Journal of the American Chemical Society, 2018, 140(36): 11519-11525.

[40] ABRAMCHUK M, JASZEWSKI S, METZ K R, et al. Controlling magnetic and optical properties of the van der Waals crystal CrCl3−xBrx via mixed halide chemistry [J]. Advanced Materials, 2018, 30(25): 1801325.

[41] FENG Q, TANG N, LIU F, et al. Obtaining high localized spin magnetic moments by fluorination of reduced graphene oxide [J]. ACS Nano, 2013, 7(8): 6729-6734.

[42] W, WANG Z, ZHAO X, et al. Domain engineering in ReS2 by coupling strain during electrochemical exfoliation [J]. Advanced Functional Materials, 2020, 30(31): 2003057.

[43] CHUA R, YANG J, HE X, et al. Can reconstructed Se-deficient line defects in monolayer VSe2 induce magnetism? [J]. Advanced Materials, 2020, 32(24): 2000693.

[44] ZHAO X, FU D, DING Z, et al. Mo-Terminated edge reconstructions in nanoporous molybdenum disulfide film [J]. Nano letters, 2018, 18(1): 482-490.

[45] 何珂. 从磁性掺杂拓扑绝缘体到内禀磁性拓扑绝缘体——通往高温量子反常霍尔效应之路 [J]. 物理, 2020, 49(12): 828-836.

[46] ZHAO Y, LIN L, ZHOU Q, et al. Surface vacancy-induced switchable electric polarization and enhanced ferromagnetism in monolayer metal trihalides [J]. Nano Letters, 2018, 18(5): 2943-2949.

[47] CHANG C-Z, ZHANG J, FENG X, et al. Experimental observation of the quantum anomalous Hall effect in a magnetic topological insulator [J]. Science, 2013, 340(6129): 167-170.

[48] DENG Y, YU Y, SHI M Z, et al. Quantum anomalous Hall effect in intrinsic magnetic topological insulator MnBi2Te4 [J]. Science, 2020, 367(6480): 895-900.

[49] GE J, LIU Y, LI J, et al. High-Chern-Number and high-temperature quantum Hall effect without Landau levels [J]. National Science Review, 2020, 7(8): 1280-1287.

[50] OTROKOV M, MENSHCHIKOVA T Y V, RUSINOV I P, et al. Magnetic extension as an efficient method for realizing the quantum anomalous hall state in topological insulators [J]. JETP Letters, 2017, 105(5): 297-302.

[51] HUAN S, ZHANG S, JIANG Z, et al. Multiple magnetic topological phases in bulk van der Waals crystal MnSb4Te7 [J]. Physical Review Letters, 2021, 126(24): 246601.

[52] ZEUGNER A, NIETSCHKE F, WOLTER A U, et al. Chemical aspects of the candidate antiferromagnetic topological insulator MnBi2Te4 [J]. Chemistry of Materials, 2019, 31(8): 2795-2806.

[53] YAN J-Q, HUANG Z, WU W, et al. Vapor transport growth of MnBi2Te4 and related compounds [J]. arXiv preprint arXiv:211006034, 2021.

[54] LAI Y, KE L, YAN J, et al. Defect-Driven ferrimagnetism and hidden magnetization in MnBi2Te4 [J]. Physical Review B, 2021, 103(18): 184429.

[55] LI H, LIU S, LIU C, et al. Antiferromagnetic topological insulator MnBi2Te4: Synthesis and magnetic properties [J]. Physical Chemistry Chemical Physics, 2020, 22(2): 556-563.

[56] YUAN Y, WANG X, LI H, et al. Electronic states and mgnetic response of MnBi2Te4 by scanning tunneling microscopy and spectroscopy [J]. Nano Letters, 2020, 20(5): 3271-3277.

[57] HU C, DING L, GORDON K N, et al. Realization of an intrinsic ferromagnetic topological state in MnBi8Te13 [J]. Science Advances, 2020, 6(30): eaba4275.

[58] WU J, LIU F, SASASE M, et al. Natural van der Waals heterostructural single crystals with both magnetic and topological properties [J]. Science Advances, 2019, 5(11): eaax9989.

[59] TIAN S, GAO S, NIE S, et al. Magnetic topological insulator MnBi6Te10 with a zero-field ferromagnetic state and gapped Dirac surface states [J]. Physical Review B, 2020, 102(3): 035144.

[60] HU C, GORDON K N, LIU P, et al. A van der Waals antiferromagnetic topological insulator with weak interlayer magnetic coupling [J]. Nature Communications, 2020, 11(1): 1-8.

[61] YAN J Q, LIU Y H, PARKER D S, et al. A-Type antiferromagnetic order in MnBi4Te7 and MnBi6Te10 single crystals [J]. Physical Review Materials, 2020, 4(5): 054202.

[62] WU J, LIU F, LIU C, et al. Toward 2D magnets in the (MnBi2Te4)(Bi2Te3)n bulk crystal [J]. Advanced Materials, 2020, 32(23): 2001815.

[63] ALIEV Z S, AMIRASLANOV I R, NASONOVA D I, et al. Novel ternary layered manganese bismuth tellurides of the MnTe-Bi2Te3 system: Synthesis and crystal structure [J]. Journal of Alloys and Compounds, 2019, 789: 443-450.

[64] YAN J-Q, ZHANG Q, HEITMANN T, et al. Crystal growth and magnetic structure of MnBi2Te4 [J]. Physical Review Materials, 2019, 3(6): 064202.

[65] YAN J Q, OKAMOTO S, MCGUIRE M A, et al. Evolution of structural, magnetic, and transport properties in MnBi2-xSbxTe4 [J]. Physical Review B, 2019, 100(10): 104409.

[66] ZHOU L, TAN Z, YAN D, et al. Topological phase transition in the layered magnetic compound MnSb2Te4: Spin-orbit coupling and interlayer coupling dependence [J]. Physical Review B, 2020, 102(8): 085114.

[67] MURAKAMI T, NAMBU Y, KORETSUNE T. Realization of interlayer ferromagnetic interaction in MnSb2Te4 toward the magnetic Weyl semimetal state [J]. Physical Review B, 2019, 100(19): 195103

[68] YAN D Y, YANG M, SONG P B, et al. Site mixing induced ferrimagnetism and anomalous transport properties of the Weyl semimetal candidate MnSb2Te4 [J]. Physical Review B, 2021, 103(22): 224412.

[69] LI H, LI Y, LIAN Y, et al. Glassy magnetic ground state in layered compound MnSb2Te4 [J]. Science China Materials, 2022, 65(2): 477-485

[70] WIMMER S, SáNCHEZ-BARRIGA J, KüPPERS P, et al. Mn-Rich MnSb2Te4: A topological insulator with magnetic gap closing at high Curie temperatures of 45–50 K [J]. Advanced Materials, 2021, 33(42): 2102935.

[71] ORUJLU E, ALIEV Z, AMIRASLANOV I, et al. Phase equilibria of the MnTe-Sb2Te3 system and synthesis of novel ternary layered compound–MnSb4Te7 [J]. Physics and Chemistry of Solid State, 2021, 22(1): 39-44.

[72] TOPPING C, BLUNDELL S. AC susceptibility as a probe of low-frequency magnetic dynamics [J]. Journal of Physics: Condensed Matter, 2018, 31(1): 013001.

[73] CASIMIR H, DU PRé F. Note on the thermodynamic interpretation of paramagnetic relaxation phenomena [J]. Physica, 1938, 5(6): 507-511.

[74] BALANDA M. AC susceptibility studies of phase transitions and magnetic relaxation: Conventional, molecular and low-dimensional magnets [J]. Acta Phys Pol A, 2013, 124(6): 964-976.

[75] COLE K S, COLE R H. Dispersion and absorption in dielectrics I. Alternating current characteristics [J]. The Journal of Chemical Physics, 1941, 9(4): 341-351.

[76] ZANG Z, ZHU Y, XI M, et al. Layer-Number-Dependent antiferromagnetic and ferromagnetic behavior in MnSb2Te4 [J]. Physical Review Letters, 2022, 128(1): 017201.

[77] HU C, TANATAR M A, PROZOROV R, et al. Unusual dynamic susceptibility arising from soft ferromagnetic domains in MnBi8Te13 and Sb-doped MnBi2nTe3n+1 (n= 2, 3) [J]. Journal of Physics D: Applied Physics, 2021, 55(5): 054003.

[78] WU W, KIRYUKHIN V, NOH H J, et al. Formation of pancakelike Ising domains and giant magnetic coercivity in ferrimagnetic LuFe2O4 [J]. Physical Review Letters, 2008, 101(13): 137203.

[79] BAŁANDA M, SZYTUŁA A, GUILLOT M. Magnetic properties of RPdIn (R= Gd-Er) compounds [J]. Journal of Magnetism and Magnetic Materials, 2002, 247(3): 345-354.

[80] SMART J S. The Néel theory of ferrimagnetism [J]. American Journal of Physics, 1955, 23(6): 356-370.

[81] HU C, LIEN S-W, FENG E, et al. Tuning magnetism and band topology through antisite defects in Sb-doped MnBi4Te7 [J]. Physical Review B, 2021, 104(5): 054422.

[82] SCHMIDT F, HUBERT A. Domain observations on CoCr-layers with a digitally enhanced Kerr-microscope [J]. Journal of Magnetism and Magnetic Materials, 1986, 61(3): 307-320.

[83] HUBERT A, SCHäFER R. Domain theory [M]. Magnetic domains: the analysis of magnetic microstructures. Berlin, Heidelberg; Springer Berlin Heidelberg. 1998: 99-335.

[84] 林高庭. 尖晶石结构MnCr2O4单晶物性研究 [D]; 中国科学技术大学, 2019.

[85] CHOI J, CHOI S, CHOI J, et al. Magnetic properties of Mn‐doped Bi2Te3 and Sb2Te3 [J]. Physica Status Solidi (b), 2004, 241(7): 1541-1544.

[86] MYDOSH J A. Spin glasses: an experimental introduction [M]. CRC Press, 1993.

[87] MAJUMDAR A, OESTREICH V, WESCHENFELDER D. Deviations from Curie-Weiss law in AuMn and AgMn spin-glasses [J]. Solid State Communications, 1983, 45(10): 907-909.

[88] BAG P, BARAL P R, NATH R. Cluster spin-glass behavior and memory effect in Cr0.5Fe0.5Ga [J]. Physical Review B, 2018, 98(14): 144436.

[89] LI H, LI Y, LIAN Y-K, et al. Spin glass state in layered compound MnSb2Te4 [J]. arXiv preprint arXiv:210400898, 2021.

[90] GE W, SASS P, YAN J, et al. Direct evidence of ferromagnetism in MnSb2Te4 [J]. Physical Review B, 2021, 103: 134403.

[91] YOO J-W, PRIGODIN V, SHUM W, et al. Magnetic bistability and nucleation of magnetic bubbles in a layered 2D organic-based magnet [Fe(TCNE·-)(NCMe)2[FeCl4] [J]. Physical Review Letters, 2008, 101(19): 197206.

[92] KO W, KOLMER M, YAN J, et al. Realizing gapped surface states in the magnetic topological insulator MnBi2-xSbxTe4 [J]. Physical Review B, 2020, 102(11): 115402.

[93] KOEHLER W C. Magnetic properties of rare-earth metals and alloys [J]. Journal of Applied Physics, 1965, 36(3): 1078-1087.