【doc】层状膜磁光克尔效应的研究及其自动测量仪的建立

【doc】层状膜磁光克尔效应的研究及其自动测量仪的建立 层状膜磁光克尔效应的研究及其自动测量 仪的建立 南京大学 第32卷第2期JOURNALOFNAN~NGUNtVERSITYVo1.32,No.2 1996年4月(NATURALSCIENCES)Apr.,1996 STUDlYoNMoEFFECTSlN LAYEREDFILMSANDESTABLISHMENToFoPTI CONST&MoKERRSPEcTRoMETER IChunYuChadJuty?gh?0MoYoagzZhagHoag*'u (physi~I~partmentofNanjingUniversity,210093,Nanjing,PRC) AbstractAnauto— spectrorneterisestablishedformeasuringopticalconstantsandmagneto--optical Kerreffect?Opticalconstants'Kerr1~4atlonandKerrellJpticityarcmeasutodwiththisinstrument asafunctionofmagneticfieldsfrom0to士 10Oerstedsatanywavelengthbetwean320llmand 840nm?InthispaperwedescribetheresultsofapplicationofthisapparatustoaseriesofCo/Pb layered丑 1m3andFe/Phmultilay,:redfilmaampleeexhibitingtheMeeffect.Itismustratedfor theenhancementofmagneto-optical0 ,with1werrvtlcalconstants!theKerrrotationangleis largerattheshorterwavelengthinco/PhundwJc~flhrmwhenthethickn憾 sofCoisthinnor.and atthelongerwavelangthinFe/Phmuirnayectmm目whenthethicknessofPh自thinngr. Keyword~Magneto-opticaleffect'opticalconstants,Kerrr<~ation,KerrelUpticity.1ayeredfilm 0INTRoDUCTIoN Inordertogetthecompleteinformationofthemagneto-opticalmaterial,weshouldoh- tainboththediagonalandoff-diagonalelementsofmateri&lcomplexdielectrictensor.Asthe complexdielectrictensorisrelatedtotheMOmaterialsconstants0 ,opticalandmagneto-optl- cal?constructingartapparatustomeasuretheopticalconstantsandtheKerrparameters(rote- tionangleandellipttcity)isessentle2.weestablkzhedartauto-spectrometerofopticalconstant.s andame~uringsystemo,MOKerrspectra.Steppingmotorswith400stepsperrevolution ateusedtocontroJthemonochromatorandpola~r,analyzerazimuthalangle.Computerin— terraceboard,steppingmotorscontrollercirc4esandmechanicalparts&remadebyourselves. Thetechniquesofauto-feedbackandughtmodulationaleusedinM0constants.measurement. Themea~sorementsaremadeatariP-aTnormalincidentangleoflessthan5degrees.andthe maximummagneticfieldofthemagnetjs10Oersteds.Thereflectedtightisdetectedbyapho- ?Receivedl1995--05--05 :::965".ph螂.呻Ph鲥.Pco--tpft卜 .i92.南京大学(自然科学)第32卷 toelectronmultiplierwithalock-inamplifier.Theresultsofmeasurementarecomparedwith references:itshowsthattheprecisionofthsystemhighenough?Withthissystemweoh- serredtheenhancementofmagneto-opticaleffectinCo/PbsandwichfilmsandFe/Pbmulti_ layeredfilms? lEXPERIMENTALAPPARATUSANDPRINC1PLESOFTHE TECHNIQUE (a)Opticalo0nstan AschematicdiagramshowingtheprincipleofthemethodisgiveninFig?1? Thelightincidenttothesurfaceofthemetalfrommedium(n0)attheangle();bylls. iugthelawofrefraction:[see(1)to(3)] 一n1(I+)(1) 矗lsin蟊一(2) 1c0sl:?l.一缸.00(3) SincetheincidentUnearlypo/arizedtightwi//ingeneralbecomeellipticallypolarizedonrefl ee- ti0natthemetalsurface,let屯andbethephasechanges,andhandrpbetheabsolutevalus- esofthereflectioncoefficients,bytheFresn~lformulae: ;=一sin(瓦oo--Ot):I;Ie(4)— s.m(+),' tg(O00,}e(5】'一+ 1 )'.',, i, P==tg.(6) where tg=f{(7) '一 ,一(8) Asthequantitiesr,,.6I,,and5al'ea/lfunctionsofeD'and0fnandk'measurement ofanytwoofthe~equantRie~foraspecificvatueoftheangleofincidence日?willpermitthee- valuationofnandk.FromEq.(3)and(6){ =::1+tg?e.ms|nOt?tgoo(9) = + if ,:,:+(11) 期L-uChun,StudyOnMOEffectsInLayBredFilm.. I93. wewil1get where ? ? fA一日一6.+g2sinoo 1B=2ab f口=RintgOc~s2O/(1+s.m2o0sd') lb—nosJT}tgOosin2枷in#/(1+sin2排osdj) Fig-1Thedissramofapparatusformeasurin80p|jI.o?fanf3. k/4?一扯 B?, r"h, /ofinaIne' , \ /\ \ / i\ \ i\ F?2Theazimuthofthepo/arizerand analyerwhenthereflectedlight vanishod. (12) (13) (14) (15) Soifweme.~urethe andd.,wewilldeterrrline and. Inordertogetpand. weshoL衄measuretheaz- imuthofthepolarizerand Janalyzerwhenthereflected lightbecomeszero.Theo ordinatejstakenasshownin Fig-2.Itisperpendicu~trto thed~'eetion0,theught -atravellmg. ByusingJonesmatrix,theintensityoftheTeeeived 1ighIj宴: 一 = f峙一1(16)L 1』 ffwechangethevalueoftomake6.一0Or. thereflectedlightwillbecompensatedtobeline~ly polarized. When +号一2o,一0 then : 咖'+】] sin(+)j Adjusta."h1~yzerAtomakereflectedi~ghtdtmin~h (17) 训 nn S 1—2 L墨 . 19{.甫京大学(自然科学)第32卷 then so=180一? If'+罢一2= 二 when=, ^=0 Alsowhentheazimuthofthequarter—WaVeplatePsfastaxisis135.,wecanobtain fd.:270.一2 1=0 (18) (19) ...一(20) 1=180.一 SineewegettheazimuthofPandAwhenthereflectedlightvanished'wecansolutth valueofnand. (bjMagneto--opticalEffect . FormagneticmaterialswithmagnetizationMalongZdirection'thedielectrictensorand conductivitytensorcanbeexpressedas (21) ;=1一i4a/m(22) ThecomptexindexofrefractionofrightandleftcircularlypoMrizedlightisgivenby ;(;士远.)(23) whenallnearlypolarizedlightisL~cidentontoamagneticfilm,thereflectedlightise111ptical ly polarizedbeCaLlSeOfthedifferentreflectlvitiesofrightandleftcircularlypolarizedLight? At nornudincidence.;aregivenby '?_=) ThedeviationofthemajoraxisandtheelJJptlcityofthereflectedlightarecalledpolarmagne- to-optiealKerrrotation0tandpolarmagneto-opticalKerrdlipticity,xrespectively? =(+一一)/2(25) ":r+ =+r-(26) Fromeq.(21)to(26),and"canbeexpressed? . ‰kO . 第2期LJuChun,e2}StudyOnMOEffoctsInLayeredFilms…?195. 以一 一 坼= ' .+Be)一i(A A0+B0 A=(--++3nk.);B一(p+,3) ir:s一",;元:一船); Fig.3Thesc'nematicdiagramotthenulltypcauto-fecdbaekkerrspcc— tromecCT , 弋 f},一\ , 一 弋一-,4一.ELLIPSE \/ F4ArlillustrationoftheeRipticallypolarized【ightinscr~ andpenetratingtheSoleflcompensator (27) (28) Wehaveestabbeda nuLltypeaUtO—feedbackKerr spectrometer.Itisshownin Fig.3. Forthepurposeofira, provingthesensitivity,a lightmodUlalorandalock,in amplifierwereapplied.Fara— dayCellwasusedasthe modulatorwhichoperatedat 79Hzandconsistedofa solenoidsurroudingaquartz modulatedcote.Thelight sourceisXeLamp-Thellght frommonochromatorranges from32Ohmto84Onm.The angleofincidenceiskeptbelow5degreesto asBurecompletedetectionofthepoLarKerr component.Themaxin]ammagneticfieldof themagnetjs1OkGs. ThelinearlypoLarizedIighttobereflect— edfromsurfaceofthesampleinthemagnetic fieldbecomeselJiptio_.~dlypolarized;thelong axisoftheeLliptio,~ypolarizedfight(EPL) hasrotatedananglewiththeazJmu[hof thelinemlypolarizedlight:itca12edKerrto- rationangle.TheEPLhasbeenaddeda modulationangle6F_一sjn~,)twhenitpasses throughtheFaradayCel1.andthenJt'sre— ceivedatthephotoelectronrnoltiplLarbehind ? 198?南京大学(自然科学)第32卷 theal脚yzer? Supposethepolarizerthedirectionofy,analyzerAhasanangMwlthX-&'ds(ais inproportiontothevalueofcompensatedcurrent)一ByMainslaw,theintensityof?ghtr eeivedbyphotoelectronmunipl/er! ,=10COg(导一巩,一.)=1.(1一cosE2(0,+.)+2])(29?) ByusingBesselFunctionandlock—inbasefrequence: IB=,0sin2(+n),1(2p)(29b) when +a=导.,:0.巩:詈一?(30a) Inpracticalmeasurement,toeliminatetheinfluenceofrefxection,廿lisobtainedbyreversing thedirecti0nofthemagneticfield.Thus 巩一(dl+,'一)/2(gOb) here?isthecurrentvalueforpositiveandnegativemagneticfields. TheKerreliipticity"wasmeasuredinthesamewayasKerrrotationifaSoleil-Babinet compensatorwagmountedbetweensampleandFaradayCe/l—Theprincipleofthemeasure-? mentjsasfollows. Fig-4isanillustrationoftheelUpticallypolarizedJightbeforeandafterinsertingtheSolefl compensator-Thelinearlypolarizedlightbecomesane11ipticallypolarizedlightafterreflection fromthesample.IntheX—Ycoordinatesystem,theeLlipsecanbeexpressed?: ,=口cos,c璐一bsinm,sin以{,=?cosms.m+6咖mcos.D where6/?=e_.WhenthefastaxisofthecompensatorisalignedtotheX-axis,Y-axistom— ponentoftheelectricfieldvectorisinvariable,butthephaseoftheX-axiscomponentshiftsa- headbyn/2.ThereforeXcomponentoftheelectricfieldvectorofthenewell/pseisgivenby: 日,=,?sin,oos一6c嘴凸J,sin-(32) SinceBkandareusuallymuchsmallerthan1,theelectricfieldvectorofthenewellipse canbeexpresedapproximatelyas: E,=?cos(?+?/2)(33) ,:口(+)1/2c喁(m+?)(34) where c??:/(以+e).(35) sin?=一/(+:).(36) FromEqs.(33)-(36),therotationofthemajoraxisofthenewellipsecanbeobtained: tg2a=2e/(1一+e)(37) Considerthatand&remuchsmallerthan1,onecangetd=.Angleacanbemeasured 第2期LiuCbun,":StudyOnMOEffectsInLayeredFilms…?197? bythesamemethodasthaiforKerrrotslion- 2EXPERlMENTALRESULTSANDDISCUss10N Withthemeasuringsystem,wehavemeasuredthickCofilmandsinglecrystalFeatthe wavelengthfrom320timto840nm.Wegetthen.koftheCofilmalsoitsspectraofmagne— to—opticalconstants,andtheoptical&MOconstantsspectraoftheFefilm. Bythesespectra,eco~rdingtothetheoryofMO: where and weobtain =+"=堡三=-?辛 A=3n一矿一 B一3一+n iIl一一) e12一(3一一k)+h(3nk一+) e" I2一巩(3nk一+)一(3n^一一) ,一 . ,一 2nk (38) Sowegetthediagonalandoff-diagonalelementsofthesample~complexdielectrictel~or, whereandIaretherealandimag/narypartofthediagonalelementsrespectively;2and gll1 2aretheseofoff-diagonalelements.ThespectrafordielectrictensorsoftheCoandFe丘lJ" aregiveninFig5andFig.6. 10awlt~ngth(^) Fig-5SpectraofdielectrictensorintheCofilm : .}--E~l;l一 ,一II,『 . 一 I{l/.f 345678 . L一,:'二jlnBthfA) Fig-6SpectraofdielectrictensorintheFe(single crysta1) Wealsoobtainthespectraoftheopticalconstantswhichrespectivelyrepresentsamplesof 30Co/1002Ph/30Co,lOOCo/1O00Ph/lOOCoand150Co/lO00Pb/150Co.Thesethreesam ples comparedwithConImsisshowninFig.7. 98?南京大学(自然科学)第32卷 101~llngttlt^) Fig.7Kerrrotatio~spectraofCo,30Co/1002Pb/ 30Co,1OOCo/1000Pb/100Coand150Co/ 1OOOPb/l50Co 03w_ngmt^ Fig.9KerrrotationandellipticityspectraofCoand 100co,l000Pb/l00Co -0…bq(^, Fig.8Diagonalelementss~etraofCoand100co/ 1000Pb/l00Co l0W~v~lerMCth(^ Fig-l0Kerrrotations~etraofFc,(30Fe/30Pb)~0 and(30Fo/1OPb)1' UromFig.7wefind.lofCo/Pbnhns上皇enhanced8ttheshortwavelength;whentheja, erofCoisthnel,.theenhancementisobvious. AccordingtotheMetheory: 一耵)(39) 丽)?) if'issmMi'the~ticalconstantsritetOW?orCIZi.e.MOconstantsislarge,日kand"are enhanced.Fig.8showsthatdiagonaJ.ebementsofCo/Pb(100Co/1000Pb/lOOCo)filmare smallei,thanCofilm's8tshortwavelength,sotheir日land"elarger.It'sshowninF_琅.9. Wealsomakemeasurementfor(30Fe/30Pb)20and(30Fe/10Pb)19samples.Kerrrota- l!?g?id 第2期LiuChun.etat:StudyOnMOEffectsInLayeredFilms….[99. tionsofthesetwosamplesarecomparedwiththeFcfilm's.ItjsgiveninFig.10. Fromthemeasurementresults,wehaveobservedthatofFe/PbfilmsislargerthanFe firm'satlongwavelength.WhenthethicknessofPhlayerjSthinner,theenhancementis larger,nandkoftwoFe/PbsamplesarecomparedwiththatofFefilm'sttheyateshownre— spectivelyinFig.11andFig.12tfromthem,wecouldseetheopticalconstantsofFe/Pbfilms aresmallerthanFefinn'satthelongerwavelengthtitmakestheenhancement. &5 S 2.5 2 05 10wa~agth(^ Fig-11^spectraofF.,(30Fe/3OPb)~and(30Fe/Fig.12tspectraofFe,(30Fe/30Pb)Hand(30Fo/ 10Pb)l'10Pb)1. 0 06 善nV 王n ? 0 E02J m1 00 Fig?13Compar~onbetweenexperimentalandnu.F. 崛.14Comparisonbetw~nexperimentalandnu— meriealealculationre.stiltsofCofilmmeric.~dcalculationrcsuI眙ofFe Finallywemakeacomparisonbetweenthetworesultswhichareexperimentalandnumerical ealculatinnsaccordingtotheMOtheory;theresultsshownatFig.13andFig.14areagreeable andaccllrate. ? 200.南京大学学撤(自然科学)第32卷 Re[ere.ees 】 MaxBorntEmilWolf.PrinciplesofOptics.6fbed.OyA~ord,NewYork,Toronto,sy0ney,Par坶t Frankfurt:PergamonPress,1980.I,7I6 2LandauLD?Li~hizEM.Eleetrodynamiesofcontinuousmedia.London:pergamon.I960.58~60 3KaCayamaT,SuzukiY?A~~aeloH.e2a1.En~neementofeheMagneto-Opt0~iK甜 rRorationinFeu mlayeredFilms.PhysRevLetf'I988.B0:142fi~I429 4ReimW.WellcrD.KerrrotationenhanccmencinmetMliebi~yerthinfilmsformagnet~--opticalrecord— ing.ApplPhysLet~,1988.53,245~2454 5The~aisPS?GdoutosEE.MatrixTh~ryofPho~oelastieity.Berlin:Spinger,I979 6MansuripulMasud,Fcngloi?KevlnErwinJ-Measuringthewavelengthde删 en.cofmagnetoopti- calKerrorFradayrotationandcWpt~tylatechnique.AoplOpti一1990,29(9):1308~I331 7xuyongbin,JinQinyuan?LuMu,".MeasurementofCOmple~MOspectraandstudyofmultih er8.ChineseJofNationMCofff.orlMagnetism.1993.8:53 8Krumm~JP'OorrnannV?klagcsCP.Moasu~-omcntofthemagnetooptiepropertiesofbismuth-substitut- edirongranetnIm3usingpiezo~irefringentmodulation.App】Opti,1984,23(8) 一 6 Il 层状膜磁光克尔效应的研究及其 自动测量谱仪的建立午》. ? 刘淳"俞超"金永红苗永智"瞿宏如.__—?-?_-- 一一 (I)南京大学物理系.219098,南;2)南京大学电子 工程 路基工程安全技术交底工程项目施工成本控制工程量增项单年度零星工程技术标正投影法基本原理 系.210093,南京 3)南京大学现代分析中心,210093,南:) 摘要获取磁光材料较全面的舟电张量对角元和非对角元复量谱为目的.建立了光学常数 谱和磁光常数谱韵自动测量系统阐述了测量系统的理论基础.将测量波长范围拓宽到3299A 至8400A,能够}肄I量磁光材料的光学常数,磁光克尔旋转角和克尔椭偏率.从而得到材料磁光 常数完整的信息运用所建立的系统,对单层厚co膜,单品Fe,Co/Pb系列夹层膜和Fe/Pb系 刑多层膜进行了系统测量和计葬,得到了其升电张量对角元和非对角元复量谱.同时对层状膜 的磁光效赢及增强.进行了尝试性的研究.在Co/Pb夹层膜系列样品中.发现当Co的厚度较小 时.在短波方向有克尔角的增大;在Fe//,b多层膜系列样品巾,发现当Pb的厚度较小时,在长 渡范围也有磁光效应的增强. 关键词磁光效应,光学常数,克尔旋转角.克尔椭倍率.层妆膜 分娄号订一,一