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1、1906Chem.Mater.2004,16,1906-1913MoleculeDerivedSynthesisofNanocrystallineYFeO3andInvestigationsonItsWeakFerromagneticBehaviorSanjayMathur,*,²MichaelVeith,*,³RasaRapalaviciute,³HaoShen,²GerardoF.Goya,§WaldirL.MartinsFilho,§andThelmaS.Berquo§Leibniz-InstituteofNewMateri
2、als,CVDDivision,D-66123Saarbruecken,Germany,InstituteofInorganicChemistry,SaarlandUniversity,D-66123Saarbruecken,Germany,andInstituteofPhysics,UniversityofSaÄoPaulo,CP66318-05389-970SaÄoPaulo,BrazilReceivedNovember21,2003.RevisedManuscriptReceivedFebruary6,2004AnewY-F
3、ealkoxide,[YFe(OPri)6(PriOH)]2,isusedinthesol-gelprocesstoobtaintheorthoferrite,YFeO3.TheY/Festoichiometry(1:1)andY-O(R)-FechemicallinksinthesinglemolecularprecursorkineticallycontroltheformationofmetastableYFeO3whichisotherwisedifficulttoprepareduetotheeasyformationo
4、fthegarnetcomposition,Y3Fe5O12.TG/DTAanalysisshowedthecrystallizationofYFeO3at680°C,whichwasconfirmedbyXRDdata.Thepowdersobtainedwerenanocrystalline(TEM)andtheonlycrystallinecompoundpresentbetween600and1300°CwasmonophasicYFeO3.Theabsenceofgarnetandotheriron-containing
5、residualphasesobservedinpreviousstudieswasconfirmedbytemperature-dependentMoÈssbauerandmagnetizationmeasurements.Themagnetizationdatasupportaweakferromagneticbehaviorandreveallow-andhigh-fieldregimesinM-TandM-Hcurves,correspondingtomagnetocrystallineandantisymmetric-e
6、xchangeanisotropy,respectively.Introductionespeciallyimportantwherethesimultaneousgrowthofdifferentphasesandthepresenceofmetastablecom-Chemicalsynthesisofnanomaterialsisbasedonthepoundsinthephase-diagrammakethephase-selectivetransformationofmolecularcompoundsintomater
7、ialssynthesisadifficulttask.Forinstance,thesynthesisinwhichthestructuralunitspresentintheprecursorofthetitlecompound,YFeO3,isnotstraightforwardmoleculearecarriedforwardtothetargetsolid-statebecauseofthepreferredformationofY3Fe5O12(YIG)structure.1-5Thisstrategyprovides
8、themeanstogrowcompositionintheY2O3-Fe2O3system.11Althoughathesolid-statestructuresfrommolecularªseedsº.Fornumberofreports12-
