新型強關聯(lián)電子材料電子態(tài)和磁性研究.pdf

1、中國科學院合肥物質科學研究院博士學位論文新型強關聯(lián)電子材料電子態(tài)和磁性研究姓名：王維華申請學位級別：博士專業(yè)：凝聚態(tài)物理指導教師：鄒良劍20070501英文摘要AbstractElectronicstatesandmagneticinteractionsbetweenlocalspinsintwotypesofnewstronglycorrelatedelectronsystems，Mndopeddilutedmagneticsemic

2、onductors(DMS)andNa2C002，areinvestigatedtheoreticallyinthepresentdissertationThefocusistoclarifythephysicalmechanismoftheferromagnetic(FM)longrangeorder(LRo)inDMSandthereasonoftheantiferromagnetic(AFM)insulatinggroundsta

3、teinNao5C002Themaincontentsarepresentedasfollows：Atfirst，thecurrentresearchstatusofDMSandNaxC002，theopenphysicalproblemsandtheimportanceofthecontentsinthedissertationarebrieflyintroducedThen，theelectronicstatesofsingleMn

4、impurityandmagneticcouplingsbetweenMnspinsinDMShavebeenstudiedsystematicallyStartingfromtherealisticinteractionparametersinDMSs，weclearlyshowedthatinthegroundstate(GS)，theMnspinantiferromagnetically(AFM)couplestosurround

5、ingAs(N)atomsaspdhybridizationvpdislargerthanacriticalvalue億andboththePelectronlevel玩andtheimpuritylevelEdareclosetothemiddleofthegap；orveryweakFMwhen‰issmallandboth戰(zhàn)andEdaredeepinthevalencebandThisAFMpolarizationisinagr

6、eementwithwidelyobservednegativemagneticcirculardichroismsignalofAssitesMoreover，weclarifythattheanisotropicspatialchargedistributionofaMnacceptorinIIIVDMSsisowingtothatMnT293dorbitsarelessthanhalffilling，whichisinagreem

7、entwiththeimageofthescanningtunnelingmicroscopy(STM)Forhalforfullfilledporbits，themagneticcouplingenergyisproportionaltoCOS9wherepistheazimuthanglebetweenthetwoMnspinswhichistheHeisenbergAFMcoupling；onthecontrarythemagne

8、ticcouplingenergyisproportionaltocos(0／2)1whenelectronoccupationinporbitsisawayfromhalforfullfilling，whichistheessentialcharacterofthedoubleexchangelikeFMcouplingTheMnimpuritiesconcentrationisverylowintherealisticDMSAtth

9、esametime，theantisiteAscompensation，theinterstitialMnatoms，ortheholecarriersphaseseparationmakePorbitsdeviatefromhalffilling，stabilizingtheFMgroundstateinIIIVDMSDuetothestronghybridizationoftheAs(N)Porbitswiththe3delectr

10、ons，thesystemformstwohybridizednarrowbands；thehybridizedbandwithdominantdorbitalcharactercouplestotheMnlocalspinsviastrongHund’Scoupling，thusthehoppingofthemobileholesbetweenlocalizedspinsgivesrisetothedoubleexchangelike

11、FMcouplingandleadstotheFMorderinDMSsimilartothatindopedmanganitesWealsoarguethattheseresultsaboutthemicroscopicmechanismofFMLROstillholdqualitativelyforthelatticesystemsInaddition，theelectronicstatesofhomogenousandparama

12、gnetic(PM)phaseabouttheextendedsingl爭bandHubbardmodelinatwodimensionaltriangularlatticeformedbytheCoionsinNa它C002areinvestigatedbytheKotliarRuckensteinslavebosonapproachForthelowdopingconcentrationz，thehomogenousphaseism