Ferro- and Antiferroelectricity: Order/Disorder versus Displacive PDF
Preview Ferro- and Antiferroelectricity: Order/Disorder versus Displacive
124 Structure and Bonding SeriesEditor:D.M.P.Mingos EditorialBoard: P.Day·X.Duan·T.J.Meyer G.Parkin·H.W.Roesky·J.-P.Sauvage StructureandBonding SeriesEditor:D.M.P.Mingos RecentlyPublishedandForthcoming Volumes Ferro-andAntiferroelectricity IntermolecularForcesandClustersI VolumeEditors:Dalal,N.S., VolumeEditor:Wales,D.J. Bussmann-Holder,A. Vol.115,2005 Vol.124,2007 SuperconductivityinComplexSystems PhotofunctionalTransitionMetalComplexes VolumeEditors:Müller,K.A., VolumeEditor:V.W.W.Yam Bussmann-Holder,A. Vol.123,2007 Vol.114,2005 Single-MoleculeMagnets PrinciplesandApplications andRelatedPhenomena ofDensityFunctionalTheory VolumeEditor:Winpenny,R. inInorganicChemistryII Vol.122,2006 VolumeEditors: Kaltsoyannis,N.,McGrady,J.E. Non-CovalentMulti-PorphyrinAssemblies Vol.113,2004 SynthesisandProperties VolumeEditor:Alessio,E. PrinciplesandApplications Vol.121,2006 ofDensityFunctionalTheory inInorganicChemistryI RecentDevelopmentsinMercurySience VolumeEditors: VolumeEditor:Atwood,DavidA. 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Dalal· Annette Bussmann-Holder Withcontributionsby R.Blinc·A.Bussmann-Holder·N.S.Dalal·T.Egami O.Gunaydin-Sen·M.Itoh·R.Kind·D.Merunka·B.Rakvin J.F.Scott·H.Taniguchi 123 The series Structure and Bonding publishes critical reviews on topicsof research concerned with chemicalstructureandbonding.ThescopeoftheseriesspanstheentirePeriodicTable.Itfocuses attentiononnewanddevelopingareasofmodernstructuralandtheoreticalchemistrysuchasna- nostructures,molecularelectronics,designed molecularsolids,surfaces,metalclustersandsupra- molecularstructures.Physicalandspectroscopictechniquesusedtodetermine,examineandmodel structuresfallwithin thepurviewofStructureandBondingtotheextent thatthefocusisonthe scientificresultsobtainedandnotonspecialistinformationconcerningthetechniquesthemselves. Issuesassociatedwiththedevelopmentofbondingmodelsandgeneralizationsthatilluminatethe reactivitypathwaysandratesofchemicalprocessesarealsorelevant. Asarule,contributionsarespeciallycommissioned.Theeditorsandpublisherswill,however,always bepleasedtoreceivesuggestionsandsupplementaryinformation.PapersareacceptedforStructure andBondinginEnglish. InreferencesStructureandBondingisabbeviatedStructBondandiscitedasajournal. SpringerWWWhomepage:springer.com VisittheStructBondcontentatspringerlink.com ISSN0081-5993 ISBN978-3-540-49602-1SpringerBerlinHeidelbergNewYork DOI10.1007/978-3-540-49604-5 Thisworkissubjecttocopyright.Allrightsarereserved,whetherthewholeorpartofthematerial isconcerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation,broad- casting,reproductiononmicrofilmorinanyotherway,andstorageindatabanks.Duplicationof thispublicationorpartsthereofispermittedonlyundertheprovisionsoftheGermanCopyrightLaw ofSeptember9,1965,initscurrentversion,andpermissionforusemustalwaysbeobtainedfrom Springer.ViolationsareliableforprosecutionundertheGermanCopyrightLaw. 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Coverdesign:Design&ProductionGmbH,Heidelberg TypesettingandProduction:LE-TEXJelonek,Schmidt&VöcklerGbR,Leipzig Printedonacid-freepaper 02/3100YL–543210 SeriesEditor Prof.D.MichaelP.Mingos Principal St.EdmundHall OxfordOX14AR,UK [email protected] VolumeEditors NareshS.Dalal AnnetteBussmann-Holder DepartmentofChemistryandBiochemistry MPIfürFestkörperphysik andNHMFL Heisenbergstr.1 FloridaStateUniversity 70569Stuttgart,Germany Tallahassee,FL32306,USA [email protected] [email protected] EditorialBoard Prof.PeterDay Prof.GerardParkin DirectorandFullerianProfessor DepartmentofChemistry(Box3115) ofChemistry ColumbiaUniversity TheRoyalInstitutionofGreatBritain 3000Broadway 21AlbermarleStreet NewYork,NewYork10027,USA LondonW1X4BS,UK [email protected] [email protected] Prof.HerbertW.Roesky Prof.XueDuan InstitutforAnorganicChemistry Director UniversityofGöttingen StateKeyLaboratory Tammannstr.4 ofChemicalResourceEngineering 37077Göttingen,Germany BeijingUniversityofChemicalTechnology [email protected] 15BeiSanHuanDongLu Beijing100029,P.R.China Prof.Jean-PierreSauvage [email protected] FacultédeChimie Prof.ThomasJ.Meyer LaboratoiresdeChimie Organo-Minérale DepartmentofChemistry UniversitéLouisPasteur CampusBox3290 4,rueBlaisePascal VenableandKenanLaboratories 67070StrasbourgCedex,France TheUniversityofNorthCarolina [email protected] andChapelHill ChapelHill,NC27599-3290,USA [email protected] StructureandBonding AlsoAvailableElectronically For all customers who have a standing order to Structure and Bonding, we offer the electronic version via SpringerLink free of charge. Please contact yourlibrarianwhocanreceiveapasswordorfreeaccesstothefullarticlesby registeringat: springerlink.com Ifyoudonothaveasubscription,youcanstillviewthetablesofcontentsofthe volumesandtheabstractofeacharticlebygoingtotheSpringerLinkHome- page,clickingon“BrowsebyOnlineLibraries”,then“ChemicalSciences”,and finallychooseStructureandBonding. Youwillfindinformationaboutthe – EditorialBoard – AimsandScope – InstructionsforAuthors – SampleContribution atspringer.comusingthesearchfunction. Preface Solid-statesystemsarefrequentlyclassifiedaccordingtotheirphysical,struc- turalorchemicalproperties.Suchschemesareextremelyhelpfulsinceprop- ertiesrelatedtoanysuchclassificationaretypicallyknownandfacilitateiden- tifyingsolidswithspecialmaterialclasses.Thebest-knownexamplesofthese schemesareconductivityorresistivitymeasurementsbymeansofwhichmet- als are easily distinguishable from insulators. However, frequently clear-cut decisionsbetweenmaterialclassesarenotpossible,sinceanisotropy,chemical composition,bindingforcesandlocaleffectswashoutdistinctpropertiesand leadtocompetitionorcoexistence. Suchunresolvedsituationsareespeciallytypicalfortransitionmetaloxides that exhibit a variety of ground-state properties in a fascinating way. Here chemicalsubstitution,doping,pressureortemperatureeffectseasilyinfluence thephysicalpropertiesandmay,forinstance,inducemetal/insulator,antifer- romagnet/ferromagnet, insulator/superconductor transitions. This situation isanalogoustoperovskiteferroelectricsandhydrogen-bondedferroelectrics, whereferroelectric/antiferroelectrictransitionsoccurwithchemicalsubstitu- tionsofoneoftheconstituentsublattices.Inaddition,glass-likestates(dipolar glasses)areobservedandrelaxorferroelectricitywithalargepotentialforap- plicationfrequentlyoccurs. Ferroelectrics and antiferroelectrics have a long history, and their phase transitionmechanismhasearlyonbeenclassifiedaccordingtoexperimental observations. In1960 softmodedynamics wereseen inperovskiteoxidesby inelastic neutron scattering, following theoretical predictions by Anderson and Cochran in 1959. A long wavelength optic mode frequency slows down withdecreasingtemperatureandfreezesoutatT .Thedisplacement pattern c oftheionsinvolvedinthesedynamicsdeterminesthelowtemperaturepolar structure. These features have been attributed to displacive dynamics and opposed to order/disorder ones where above T a specific ion many occupy c various equivalent lattice sites and hop between those. At T the ion orders c into either of these sites thus giving rise to the polar state. Both transition mechanismsarebasedonadouble-wellpotential,however,withthedistinction thatthebarrierheightforadisplacivetransitionismuchsmallerthantheone fortheorder/disordertransition. X Preface In1979ithadalreadybeen suggestedbyBruce,MüllerandBerlingerthat aclear-cutdistinctionbetweenorder/disorderanddisplacivedynamicsisnot possible. It has been pointed out that different timescales may be associated with the different dynamics and that specifically EPRexperiments would be an excellent probe to test these ideas. EPR is a local probe and can as such test dynamics associated with cluster formation whereas X-ray and neutron scattering experiments only probe the long wavelength average properties. EventhoughtheirsubsequentEPRexperimentsindeedprovidedevidencefor order/disorder dynamics in BaTiO and SrTiO , these observations induced 3 3 acontroversysinceotherexperimentswereinsupportofthedisplacivepicture. This controversial situation could be resolved theoretically by showing that bothdynamicscancoexistondifferenttimescales.Whilethelongwavelength propertiesaredominatedbymodesoftening,thefinitemomentumexcitations exhibitorder/disorderdynamics. Eventhoughthisapproachhasbeenacceptedrapidlyforperovskiteferro- electrics,itremainedunclearinhowfaralsohydrogen-bondedferroelectrics needed a novel classification scheme. Since ferroelectricity was first exclu- sively discovered in hydrogen-bonded systems, the obvious conclusion was thatthehydrogenbondsareactivelyinvolvedinthephasetransitionmecha- nism. The observationthat the protonsoccupya double-wellpositionabove T hassupported theassumption thatthedynamicsareorder/disordertype, c where a spontaneous cooperative freezing of the protons into either of the twositestakesplaceatT .Theincompletenessofthisapproachbecameclear c through high-resolution X-ray diffraction experiments which revealed that T correlates with the oxygen–hydrogen–oxygen bond length. This finding c has initiated theoretical work where a new approach was made in order to understand the dynamical details of hydrogen-bonded ferroelectrics. Here aspects that are important in perovskite ferroelectrics, i.e., nonlinear polar- izabilityeffects,havebeencombinedwiththedetailsofthehydrogenbonds. As aconsequence acoupleddouble-wellproblemwasintroduced where dis- placive features related to the heavy ion sublattice are combined with the order/disorderdynamicsofthehydrogenbonds.Thepredictionsofthemodel weresoontestedbyultra-highresolutionNMRexperimentsandaverification of the coexistence achieved. In contrast to perovskites, here the combined dynamicsobeythesametimescales. Sincetheissueoforder/disorderversus(orwith)displaciveaspectshasre- mainedanactivefieldofresearch,mostofthechapterspresentedinthisbook are devoted to it. In addition, new fields of applications are reviewed, since material optimization has considerably enlarged this area. A new aspect of ferroelectricityhasbeendiscoveredrecentlybythefindingofisotope-induced ferroelectricity in the quantum paraelectric SrTiO . Here conclusive ideas 3 aboutitsmicroscopicoriginarestillmissingandalsotheexperimentalsitua- tionremainscontroversial,sincethesymmetryofthelow-temperaturephase is unclear. But, there seems to be stringent evidence that polar clusters are Preface XI formedfaraboveT .SimultaneouslyRamanscatteringexperimentsreportthe c observation ofa softmode. Bothofthese findings again support the picture ofacoexistenceoforder/disorderanddisplacivedynamics. Themicroscopic originofrelaxorferroelectricityisanotheropenprobleminthismaterialclass. Eventhoughvariousphenomenologicalapproacheswereabletoreproduce some aspects of these interesting materials, microscopically no understand- ing is achieved. Novel neutron spectroscopic methods are presented in one ofthechaptersinthisbook,wherehintsforthemicroscopicmechanismcan be obtained. It seems clear that far above the smeared-out transition point, fluctuating polar domains are formed that increase in size with decreasing temperature. Even though mostly a polar instability is absent, very high di- electricconstantsareobservedwhichextendoverbroadtemperatureregimes. These specifics make the material extremely interesting for applications and haveconsiderablyenlargedtheinterestinthem.ThepropertiesofSlater–Takagi groupsandtheirmovementswithinhydrogen-bondedferroelectricsarealso reviewedinthisbook.Here,thefocusisespeciallyontheregimewhereapolar glassisrealizedashasbeenobservedinmixedcrystalsofRDPandADP.The competitionbetweenferroelectricityandantiferroelectricityinducesthisstate andleadstofrustrationatcertainmixinglevels. Althoughferroelectricsandantiferroelectricshavealonghistory,thepresent book shows that in spite of considerable experimental and theoretical work thefieldremainsfullofsurprisesandnewchallenges. TallahasseandStuttgart, NareshS.Dalal November2006 AnnetteBussmann-Holder Contents Order/DisorderVersusorwithDisplaciveDynamicsinFerroelectricSystems A.Bussmann-Holder·N.S.Dalal . . . . . . . . . . . . . . . . . . . . . 1 ExperimentalEvidencefortheCoexistenceofOrder/DisorderandDisplacive BehaviorofHydrogen-BondedFerroelectricsandAntiferroelectrics N.S.Dalal·O.Gunaydin-Sen·A.Bussmann-Holder . . . . . . . . . . . 23 OrderandDisorderinPerovskitesandRelaxorFerroelectrics R.Blinc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 LocalStructureandDynamicsofFerroelectricSolids T.Egami . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 FerroelectricityofSrTiO InducedbyOxygenIsotopeExchange 3 M.Itoh·H.Taniguchi . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 EvidenceforFerroelectricNucleationCentresinthePseudo-spinGlassSystem Rb (ND ) D PO :A87RbNMRStudy 1-x 4 x 2 4 R.Kind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 AnharmonicandQuantumEffectsinKDP-TypeFerroelectrics: ModifiedStrongDipole–ProtonCouplingModel D.Merunka·B.Rakvin . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 AComparisonofMagneticRandomAccessMemories(MRAMs) andFerroelectricRandomAccessMemories(FRAMs) J.F.Scott . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 AuthorIndexVolumes101–124 . . . . . . . . . . . . . . . . . . . . . . 209 SubjectIndex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
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