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1、Density-functionalstudiesoftheelectronicstructureoftheperovskiteoxides:La12xCaxMnO3S.SatpathyDepartmentofPhysicsandAstronomy,UniversityofMissouri,Columbia,Missouri65211ZoranS.Popovic´andFilipR.Vukajlovic´LaboratoryforTheoreticalPhysics,InstituteofNuclearScien
2、ces-``VincÏa'',11001Belgrade,YugoslaviaUsingdensity-functionalmethods,westudytheelectronicstructuresofthelanthanum-based``double-exchange''perovskitemagnets.Antiferromagneticinsulatingsolutionsareobtainedforboththeendmembers,LaMnO3andCaMnO3,withinthelocaldens
3、ityapproximation~LDA!,withtheJahn-Teller~JT!distortionoftheoxygenoctrahedrontakenintoaccount.TheJTdistortionsplitsofftheMn~3d)egbandsproducinganenergygapwithintheLDA,withthebandsderivedfromthe222~z21!orbital,pointedalongthelongbasal-planeMnÐObond,occupiedandt
4、he~x2y)bandsempty.Theon-siteCoulombrepulsionandtheintra-siteexchangetermsarefoundtobe,respectively,U.8±10eVandJ.0.9eV,fromthe``constrained''density-functionaltheory.ThelargevalueofUascomparedtothebandwidthindicatesthatthemanganeseperovskiteoxidesarestronglyco
5、rrelatedsystems.©1996AmericanInstituteofPhysics.@S0021-8979~96!49208-8#Thehole-dopedmanganeseperovskiteoxides,suchaswithinclusionoftheJTdistortions.Thus,themagneticunitLa12xCaxMnO3,areprimeexamplesofsolidswithaferro-cellinourcalculationhasfourformulaunitsforL
6、aMnO3magneticconductingstatecausedbythe``doubleexchange''andtwoforCaMnO3.mechanism,wherethemagneticcouplingbetweenlocalizedTheantiferromagneticbandstructuresofLaMnO3andspinsonneighboringatomsismediatedviaconductionCaMnO3areshowninFig.1.TheobservedAForder,type
7、A11electrons.1±4Boththeend-members,LaMnOandCaMnO,fortheformerandtypeGforthelatercompound,isrepro-33ducedfromthelocal-densitycalculations.Thekeyfeaturesareantiferromagnetic~AF!insulatorswith,respectively,31314130oftheAFbandstructuresagreewiththeindependentLAPW
8、Mn~t2geg)andMn~t2geg)con®gurationsoftheMn12calculationsofPickettandSingh.AsseenfromFig.1,theions.Thelocalizedspinsofthet2gelectronsarecoupledkeyorbitalsnearEfaretheO~2p!andMn~3d)orbitalsw
