狄拉克半金属候选材料NdSbTe中的巨负磁阻效应.pdf

第34卷第3期2023年9 月【文章编号】2096-2835(2023)03-0459-06狄拉克半金属候选材料NdSbTe中的巨负磁阻效应中国计量大学学报Journal of China University of MetrologyDOI:10.3969/j.issn.2096-2835.2023.03.018Vol.34 No.3Sep.2023戴翔飞，王子，陈煜迪，张子扬，杜建华，焦志伟（中国计量大学理学院，浙江杭州310 0 18）【摘要】目的：探究狄拉克半金属候选材料NdSbTe单晶样品的新奇量子效应。方法：通过化学气相输运法制备NdSbTe单晶样品，利用X射线衍射对样品的结构进行了表征；利用物性测量系统和磁性测量系统分别测量了NdSbTe的电输运性质和磁性。结果：根据磁化率X(T)随温度的变化关系可以断定NdSbTe单晶样品在Tn3.4K 处存在磁相变，通过居里-外斯定律拟合进一步确定NdSbTe单晶在Tv处的磁相变为顺磁态向反铁磁态转变。电输运性质测量表明，在不加磁场时，NdSbTe表现出半导体的行为，随着磁场的增加，电阻随温度升高而降低，呈现出巨负磁阻效应。结论：在T=3.4K，Nd Sb T e 发生了由顺磁态到反铁磁态的相变；在2 10 0 K范围内,NdSbTe具有巨负磁阻效应，当温度 T=2 K、磁场oH=8T时负磁阻最大可以达到一99.7%，该效应可能来源于反铁磁转变与近藤散射。【关键词】反铁磁有序；巨磁阻；负巨磁阻效应；近藤散射【中图分类号】0 46 9【文献标志码】AGiant negative magneto resistance in the diracsemimetallic candidate NdSbTeDAI Xiangfei,WANG Zi,CHEN Yudi,ZHANG Ziyang,DU Jianhua,JIAO Zhiwei(College of Sciences,China Jiliang University,Hangzhou 310018,China)Abstract Aims:This paper aims to probe the novel quantum effects of the Dirac semimetallic candidateNdSbTe.Methods:NdSbTe single crystal samples were prepared by the chemical vapor transport method;andthe structure of the sample was characterized using an X-ray diffractometer.The electrical transport propertiesof NdSbTe and its magnetism were measured.Results:According to magnetic susceptibility x(T),it could beconcluded that NdSbTe single crystal had a magnetic transition at T 3.4 K.It could be further determinedof the magnetic transition of NdSbTe single crystal at Tn from the paramagnetic state to the antiferromagneticstate by fitting with the Curie Weiss law.The measurement of its electrical transport properties showed thatNdSbTe behaved as a semiconductor when no magnetic field was applied.With the increase of the magneticfield,the resistance would decrease with the increase of temperature,showing a giant negativemagnetoresistance effect.Conclusions:At T=3.4 K,NdSbTe undergoes a phase transition from【收稿日期】2023-03-12【基金项目】国家自然科学基金项目（No.51771175，12 0 0 436 1）【通信作者】焦志伟（196 7-），女，教授，博士，主要研究方向为磁电子学。E-mail:中国计量大学学报网址：460paramagnetism to antiferromagnetism.In the range of 2 10o K,NdSbTe exhibits a giant negativemagnetoresistance effect.When the temperature T=2 K and the magnetic field o H=8 T,the maximumnegative magnetic resistance can reach-99.7%,which may be attributed to antiferromagnetic transition andKondo scattering.Key wordsscattering磁阻效应(MR)是指某些材料的电阻随着外加磁场的变化而变化的现象，广泛地存在于各种金属和半导体材料中，可以应用于磁存储、传感器、磁阀等，应用前景十分广阔。但在不同的材料中,其产生的机制不同，寻找具有磁阻效应的材料以及针对其产生机制的研究一直是凝聚态物理学研究的热点1-5。根据磁阻大小可以将磁阻划分为常磁阻、巨磁阻、庞磁阻和极大磁阻等6-9。在一般材料中，磁阻通常小于5%，称为常磁阻；巨磁阻(GMR)最早在铁磁-非磁多层异质结构中被观测到，由磁场(约1/10 T)导致自旋极化层之间的电子传导，因此电阻率急剧下降1.2,10.11，其磁阻是寻常磁性材料的磁阻的10 余倍。近几年来，在拓扑材料中又观测到了庞磁阻和极大磁阻效应12-151。此外，在某些材料中,其电阻随磁场的增加而减小，呈现出负磁阻效应，如在钙钛矿锰氧化物、焦绿石和尖晶石等化合物中，由顺磁绝缘态向铁磁金属态转变过程中，在居里温度附近观察到巨负磁阻效应16-2 0 1。不同材料中负磁阻效应产生的机制不同，在钙钛矿锰氧化物中，主要是由于混合价态Mn离子之间的双交换相互作用导致的负磁阻效应2 1-2 3；拓扑半金属中，由于手性异常，当磁场和电流方向平行时，可以观测到负磁阻效应2 4-2 6 。近年来，物理学家们通过第一性原理计算预言了大量可能的拓扑半金属，并已经有部分被实验证实2 7-317。最近，理论计算预言在四方格子晶体结构的材料 LnSbTe(Ln=镧系元素)中能带结构32 在费米能级（E)附近存在孤立的狄拉克锥，其线性色散的能量范围最大，极有可能是存在时间反转对称破缺的狄拉克半金属3-36 。本文采用化学气相输运法成功合成了NdS-bTe单晶，通过了X射线衍射确定了其晶体结构，并系统研究了其磁性和电输运性质。结果表明，零场的情况下电阻随着温度的降低而升高，样中国计量大学学报antiferromagnetism;giant magnetoresistance;giant negative magnetoresistance effect;kondo品呈现出半导体行为；在外加磁场的作用下，随着磁场的增大，样品半导体行为会被抑制；通过磁阻测量发现该样品具有巨负磁阻效应。这些结果表明NdSbTe在磁学和自旋电子学领域具有丰富的应用潜力，值得进一步的理论和实验研究。1实验细节1.1制备方法采用化学气相输运法，分两步生长了高质量的NdSbTe单晶。首先，将高纯度Nd（99.9%）、Sb(99.9%)和Te(99.9%)粉末按摩尔比1：1：1混合，真空密封在石英管中，在10 7 3K下烧结一周。其次，将多晶样品置于以碘（加入碘的质量浓度为10 mg/cm）为输运剂的真空石英管中，然后将石英管置于温度梯度为12 2 3112 3K的双温区管式炉中烧制7 d。在管的生长端获得了2mmX3mmXlmm的高质量单晶，如图1。2mm图1NdSbTe的单晶样品Figure 1Single crystal sample of NdSbTe1.2性质表征在室温下利用X射线衍射仪XRD（波长为1.54A（1A=0.1n m），日本理学电机公司，FA2104)对NdSbTe单晶样品的结构进行表征。第34卷第3期NdSbTe电输运性质通过物性测量系统PPMS（2 K,9 T,美国量子设计公司,PPMS-9T)进行测量,磁性是通过磁性测量系统 MPMS(1.8 K,7 T,美国量子设计公司，MPMS-7T)进行测量。2结果与讨论2.1晶体结构图2 为NdSbTe样品的XRD精修图谱，插图为晶体结构图。利用GSAS软件和Riet-veld精修的方法确定了样品的结构。精修后主峰位置（红色)和实验结果（蓝色）是相互对应的，精修结果表明NdSbTe样品为四方结构，空间群为P4/nmm,r因子为Rwp=18.79%，样品的晶格常数分别为 a=4.34 A,b=4.34 A,c=9.60 A(=90,=90,=90)。(cne)/20图2 NdSbTe的XRD精修图谱Figure2XRD spectrum of NdSbTe2.2NdSbTe的磁化率随温度变化的关系通过零场冷却（ZFC)和场冷却（FC)测量样品磁化率（X)随温度变化的关系，其中磁场平行于ab面，大小为50 0 mT。如图3(a),ZFC-FC曲线重合，磁化率在3.42 50 K范围内均随温度的降低而增加，在T=3.4K处出现了尖峰，低温下磁化率随温度的降低而降低。尖峰的出现意味着该温度下发生了磁相变。为了进一步确定样品产生的磁相变类型,对TN以上顺磁(PM)相的摩尔磁化率X(T)根据居里-外斯定理进行了拟合：X=C/(T-cw)。(1)式(1)中,X是摩尔磁化率,C为摩尔居里常戴翔飞等：狄拉克半金属候选材料NdSbTe中的巨负磁阻效应数，T为温度，w为居里温度。图3(b)为oH=500mT磁场下的磁化率倒数与温度的关系(x（T)和拟合结果。结果表明，在温度10 K以上（T)数据随温度下降线性下降，在10 K以下，曲线偏离线性。采用图中T=102 50 K 的数据利用式(1)进行拟合。拟合结果为C0.052cmKmol-1,外斯温度 cw一3.6 K，接近T的值，由拟合的C值获得的有效磁矩（er）为3.6 B，与理论预言的Nd3+离子的有效磁矩(er=gJ（J+1)1/2 B=3.62 B;（g J=8/11，J=9/2)）一致。cw为负值表明Nd3+离子之间的是反铁磁相互作用。3.0(_1ou,uo.3.53.02.52.5(-Jou ,uo s-01)/X实验值理论值误差NdSbTeBragg峰位NdSbTe;Bragg峰位406020/()461ZFCT=3.4K-FCMoHlabuoH Il abMoH=50mT12.0MoH=50 mTRup=18.79%2.0R,=13.78%1.5NdSbTe78.88%0008000NdSbTe80100-01/X1.51.0051015202530T/K1.00.50051204MoH II abMoH=50 mT3200(b)磁场沿ab面的Curie-Weiss拟合曲线与实验曲线的对比图3NdSbTe的磁化率与温度的依赖关系Figure 3 Temperature dependence of magnetic sus-ceptibilityof NdSbTe2.3 NdSbTe的 p一T关系在外加磁场分别为0 T、2 T、4T、6 T 和8 T,外加电流为1mA条件下，NdSbTe样品在2 50(a)ZFC和FC的变化曲线(C/T-Ocw)-150100T/K100T/K150150200200250250462250K的电阻率（p）随温度变化曲线如图4（a）、4(b），其中插图为磁场为8 T情况下dp/dr曲线。如图4(a)，磁场为0 T时，在2 2 50 K范围内，随温度的降低而单调增加，在低温区域电阻急剧增大，样品在呈现出半导体行为；当磁场为2 T时，其电阻随温度变化行为与零场下类似，但低温区的电阻峰值下降,约为零场时的1/7,意味着样品存在负磁阻效应。如图4（b），当磁场增加到4T以上，样品电阻率随温度的降低先升高到达最大值后继续降低，在低温下达到最小值；并且最大值的位置随着磁场的增加向高温方向移动，对磁场下的电阻p取一阶导数进行分析，如图4(b）插图所示，发现p的一阶导数存在两个转变温度第一个转变温度T1=5K附近,第二个转变温度T,=38K附近。样品电阻率的这种异常行为可能和样品的磁转变有关。3.22.82.4(-o.U.50D)/d2.01.61.20.80.40-0.400.70.6(-uo.U 01)d0.50.4上0.30.20.100图4磁场下电阻率（pxx）随温度（T)的依赖关系曲线Figure 4Temperature dependence of resistivity inmagnetic field中国计量大学学报在Kondo材料中会出现p随温度的降低而减小，然后出现一个饱和区域，紧接着电阻继续降低的行为2 41,NdSbTe样品电阻率在低温下的出现最小值可能由来自Nd的f层电子存在近藤散射(Kondo)。2.4NdSbTe的巨负磁阻效应MR是一种重要的测量方法，用于推断载流子与磁性材料中磁自由度之间相互作用,定义为MR=(p(H)-p(0)/p(0)JX100%。(2)式(2)中，MR是磁阻，p(H)为磁场下的电阻率，p(0)为零场下的电阻率。NdSbTe的磁阻随磁场的变化关系如图5，当T=2K时，低场时样品的磁阻随磁场的增加而增大并达到最大值（最大可达一99.7%），呈现出正磁阻效应，随后随着磁场的继续增加而急剧减小并很快接近饱和，呈现出明显的负磁阻效应，当磁场为8 T时可达一9 9.7%,在温度T=5K,10K时，其磁阻随磁场变化的行为与2 K的行为类似，uoH II c-axis均观测到了正磁阻效应和巨负磁阻效应，饱和值uoH=O T+2T50100T/K(a)0 T、2 T 下px-T曲线201510p/dp50-5T-10-15-20050100150200250T/KMoH=4 T6T8T50100T/K(b)4 T、6 T、8 T 下px-T曲线第34卷也是接近一99.7%。低场下出现的尖峰行为可能由于反弱局域化所致2 4，而高场下的巨负磁阻效应可能与磁相变有关。当温度高于2 0 K正磁阻效应消失，仅有负磁阻效应；而当温度高于10 0 K时，负磁阻效应也彻底消失，这可能与磁有序消失有关，其产生的机制还有待进一步研究。150200oH=8 TMoHlc-axis150200250250200-20%/AN-40-60-80-100-8-6-4-202468AoH/T图5NdSbTe不同温度下磁阻随磁场的变化曲线Figure-5Variation curve of MR with magnetic fieldfor NdSbTe at different temperatures3结语本文在成功制备了狄拉克半金属候选材料uoH II c-axis2K5K10K20K50K￥10 0 K-99.67%第3期NdSbTe单晶样品的基础上,系统研究了其磁性和电输运性能，结果表明，该样品在低温下表现出反铁磁性并伴随着巨负磁阻效应，当温度T=2K、磁场oH=8T时，负磁阻最大可达到一99.7%；近一步分析确认其负磁电阻可能是由于反铁磁相变和近藤效应引起的，其产生的机制还有待进一步研究。【参考 文献】1DIENY B.Giant magneto resistance in spinvalve multilay-ersJJ.Journal of Magnetism and Magnetic Materials,1994,136(3):335-359.2PARKIN S,S P.Giant magnetoresistance in magneticnanostructures J.Annual Review of Materials Science,1995,25(1):357-388.3ASAMITSU A,TOMIOKA Y,KUWAHARA H,et al.Current switching of resistive states in magnetoresistivemanganitesJJ.Nature,1997,388(6637):50-52.4BIBES M,BARTHELEMY A.Oxide spintronicsEJJ.IEEETransactions on Electron Devices,2007,54(5):1003-1023.5LEE P A,RAMAKRISHNAN T V.Magnetoresistance ofweakly disordered electronsJJ.Physical Review B,1982,26(8):4009-4012.6FREITAS P P,FERREIRA R,CARDOSO S,et al.Mag-netoresistive sensors J.Journal of Physics:CondensedMatter,2007,19(16):165221-165243.7CAMLEY R E,BARNAS J.Theory of giant magnetore-sistance effects in magnetic layered structures with antifer-romagnetic couplingLJ.Physical Review Letters,1989,63(6):664-667.8MILLIS A J,LITTLEWOOD P B,SHRAIMAN B I.Double exchange alone does not explain the resistivity ofLai-Sr,MnOsLJ.Physical Review Letters,1995,74(25):5144-5147.9ABRIKOSOV A A,Quantum magnetoresistanceLJJ.Physi-cal Review B,1998,58(5):2788-2794.10BAIBICH MN,BROTO J M,FERT A,et al.Giantmagnetoresistance of（0 0 1)Fe/(0 0 1)Cr m a g n e t i c s u p e r-latticesJ.Physical Review Letters,1988,61(21):2472-2475.111BINASCH G,GRUNBERG P,SAURENBACH F,et al.Enhanced magnetoresistance in layered magnetic struc-tures with antiferromagnetic interlayer exchangeJ.Phys-icalReviewB,1989,39(7):4828-4830.12ALI M N,XIONG J,FLYNN S,et al.Large non-satura-ting magnetoresistance in WTe2 JJ.Nature,2014,514(7521):205-208.13 LIANG T,GIBSON Q,ALI M N,et al.Ultrahigh mob-ility and giant magnetoresistance in the Dirac semimetal戴翔飞等：狄拉克半金属候选材料NdSbTe中的巨负磁阻效应Nature,1997,386(6621):156-159.21ZENER C.Interaction between the d shells in the transi-tion metalsJJ.Physical Review,1951,81(3):440-444.22ANDERSON P W,HASEGAWA H.Considerations ondouble exchangeJJ.Physical Review,1955,100(2):675-681.23DE GENNES P G.Effects of double exchange in magneticcrystalsLJJ.Physical Review,1960,118(1):141-154.24BUSCHOW K H J,VAN DAAL H J.Evidence for thepresence of the kondo effect in the compound CeAlz J.Physical Review Letters,1969,23(8):408-409.25XIONG J,KUSHWAHA S K,LIANG T,et al.Evi-dence for the chiral anomaly in the Dirac semimetal Na BiJJ.Sc i e n c e,2 0 15,350(2 6 59):413-416.26HUANG X,ZHAO L,LONG Y,et al.Observation ofthe chiral-anomaly-induced negative magnetoresistance in3D Weyl semimetal TaAsJ.Physical Review X,2015,5(3):031023(1-9).27BRADLYN B,ELCORO L,CANO J,et al.Topologicalquantum chemistryLJJ.Nature,2017,547(7663):298-305.28VERGNIORY M G,ELCORO L,FELSER C,et al.Acomplete catalogue of high-quality topological materialsJJ.Nature,2019,566(7745):480-485.29ZHANG T,JIANG Y,SONG Z,et al.Catalogue of to-pological electronic materials J.Na tu r e,2 0 19,56 6(7745):475-479.30VERGNIORY M G,WIEDER B J,ELCORO L,et al.All topological bands of all nonmagnetic stoichiometric463Cd,As2JJ.Nature Materials,2015,14(3):280-284.14SHEKHAR C,NAYAK A K,SUN Y,et al.Extremelylarge magnetoresistance and ultrahigh mobility in the to-pological Weyl semimetal candidate NbPJJ.Nature Phys-ics,2015,11(8):645-649.15SINGHA R,PARIARI A K,SATPATI B,et al.Largenonsaturating magnetoresistance and signature of nonde-generate Dirac nodes in ZrSiSJJ.Proceedings of the Na-tional Academy of Sciences,2017,114(10):2468-2473.16RAMIREZ A P.Colossal magnetoresistanceJJ.Journalof Physics:Condensed Matter,1997,9(39):8171-8201.17TOKURA Y.Critical features of colossal magnetore-sistive manganites J.Reports on Progress in Physics,2006,69(3):797-853.18MCCORMACK M,JIN S,TIEFEL T H,et al.Verylarge magnetoresistance in perovskite-like La-Ca-Mn-Othin filmsJ.Applied Physics Letters,1994,64(22):3045-3047.19SHIMAKAWA Y,KUBO Y,MANAKO T.Giant magnetoresistance in Tiz Mn2O with the pyrochlore structureJJ.Na t u r e,1996,37 9(6 56 0):53-55.20RAMIREZ A P,CAVA R J,KRAJEWSKI J.Colossalmagnetoresistance in Cr-based chalcogenide spinels JJ.464materialsJJ.Science,2022,376(6595):9094-9097.31王胜，郑鑫，陈浩泽，等.拓扑半金属MoTe1.5So.5与MoTe2电子结构和光学性质的比较研究J.中国计量大学学报，2021,32(2):267-273.WANG S,DENG X,CHEN H Z,et al.Comparativestudy on the electronic structure and optical properties oftopological semimetal MoTel.5 So.5 and MoTe2 LJJ.Journalof China University of Metrology,2021,32(2):267-273.32 KLEMENZ S,HAY A K,TEICHER S M L,et al.Therole of delocalized chemical bonding in square-net-based to-pological semimetalsLJ.Journal of the American ChemicalSociety,2020,142(13):6350-6359.33 HOSEN M M,DHAKAL G,DIMITRI K,et al,Discov-中国计量大学学报ery of topological nodal-line fermionic phase in a magneticmaterial GdSbTeLJJ.Scientific Reports,2018,8(1):13283(1-7).34YUE S,QIAN Y,YANG M,et al.Topological electron-ic structure in the antiferromagnet HoSbTeJJ.PhysicalReviewB,2020,102(15):155109-155115.35REGMI S,DHAKAL G,KABEER F C,et al.Observa-tion of multiple nodal lines in SmSbTeJ.Physical ReviewMaterials,2022,6(3):L031201(1-7).36PANDEY K,BASNET R,WEGNER A,et al.Electronicand magnetic properties of the topological semimetal candi-date NdSbTeJJ.Physical Review B,2020,101(23):235161-235169.第34卷（上接第356 页）64 CHEN L,XU S,LI J.Recent advances in molecular im-printing technology:Current status,challenges and high-lighted applicationsJ.Chemical Society Reviews,2011,40(5):2922-2942.65WANG X,WANG Y,YE X,et al.Sensing platform forneuron specific enolase based on molecularly imprintedpolymerized ionic liquids in between gold nanoarraysJ.Biosensors and Bioelectronics,2018,99:34-39.66J RACHKOV A,MINOURA N.Towards molecularly im-printed polymers selective to peptides and proteins.Theepitope approachJJ.Biochimica et Biophysica Acta(BBA)-Protein Structure and Molecular Enzymology,2001,1544(1-2):255-266.67 PIRZADA M,SEHIT E,ALTINTAS Z.Cancer biomar-ker detection in human serum samples using nanoparticledecorated epitope-mediated hybrid MIPJ.Biosensors andBioelectronics,2020,166:112464(1-11).68J XING R,WEN Y,DONG Y,et al.Dual molecularly im-printed polymer-based plasmonic immunosandwich assayfor the specific and sensitive detection of protein biomark-ersJJ.Analytical Chemistry,2019,91(15):9993-10000.692ZHAO J,MA Y,HOU X,et al.A novel ionic liquid syn-thesis,electrochemical polymerization,and sensing per-formance toward bisphenol ALJJ.Journal of Solid State E-lectrochemistry,2015,19(6):1571-1578.70BOSSI A,BONINI F,TURNER A P F,et al.Molecu-larly imprinted polymers for the recognition of proteins:The state of the art J.Biosensors and Bioelectronics,2007,22(6):1131-1137.71 ANDAC M,GALAEVI Y,DENIZLI A.Molecularly im-printed poly（h y d r o x y e t h y l m e t h a c r y la t e)b a s e d c r y o g e lfor albumin depletion from human serumJJ.Colloids andSurfaces B:Biointerfaces,2013,109:259-265.72CHEN A,YANG S.Replacing antibodies with aptamersin lateral flow immunoassayJJ.Biosensors and Bioelec-tronics,2015,71:230-242.73WANG Y,LUO J,LIU J,et al.Label-free microfluidicpaper-based electrochemical aptasensor for ultrasensitiveand simultaneous multiplexed detection of cancer biomark-ersJJ.Biosensors and Bioelectronics,2019,136:84-90.74ZHENG Y,ZHAO Y,DI Y,et al.In vitro selection ofDNA aptamers for the development of chemiluminescenceaptasensor for neuron-specific enolase（NSE）d e t e c t i o nJJ.RSC Advances,2019,9(27):15513-15520.75SUN L,ShEN K,ZHANG J,et al.Aptamer based sur-face plasma resonance assay for direct detection of neuronspecific enolase and progastrin-releasing peptide（31-98)J.RSCAdvances,2021,11(51):32135-32142.76李伊凡，金尚忠，姜丽，等.金纳米粒子增敏的SPRi技术应用于遗传性血栓疾病的检测J.中国计量大学学报，2022,33(3):310-316.LI Y F,JIN S Z,JIANG L,et al.AuNPs assisted detec-tion of genetic thrombotic diseases by theSPRi techniqueJ.Journal of China University of Metrology,2022,33(3):310-316.77ZHI L J,SUN A L,TANG D.In situ amplified photo-thermal immunoassay for neuron-specific enolase with en-hanced sensitivity using Prussian blue nanoparticle-loadedliposomesJJ.Analyst,2020,145(12):4164-4172.