phase evolution of layered cobalt oxides versus varying corrugation of the cobalt-oxygen ba

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1、EPJmanuscriptNo.(willbeinsertedbytheeditor)Phaseevolutionoflayeredcobaltoxidesversusvaryingcorrugationofthecobalt-oxygenbasalplaneHuaWuaMax-Planck-Institutf¨urPhysikkomplexerSysteme,N¨othnitzerStr.38,D-01187Dresden,Germanythedateofreceiptandacceptanceshouldbeinsertedlater

2、Abstract.Ageneralspin-statemodelandaqualitativephysicalpicturehavebeenproposedforaclassoflatelysynthesizedlayeredcobaltoxides(LCOs)bymeansofdensityfunctionalcalculations.Astheplanecorrugationofthecobalt-oxygenlayerdecreases,theLCOsevolvefromahigh-spin(HS)superexchange-cou

3、pledantiferromagnetic(AFM)insulatortoanalmost-HSAFM/ferromagnetic(FM)competingsystemwheretheFMcouplingismediatedviathep-dexchangebyanincreasingamountofdelocalizedpdσholeshavingmainlytheplanarO2pcharacter.Itistentativelysuggestedthatthedelocalizedholesmorethan0.3perCoO2bas

4、alsquarearelikelynecessaryfortheinsulator-metaland/orAFM-FMtransitionsinthecorrugation-weakenedLCOs.AphasecontrolmayberealizedinLCOsbyvaryingtheplanecorrugation(thusmodifyingtheholeconcentration)throughanionic-sizechangeoftheneighboringlayersonbothsidesofthecobalt-oxygenl

5、ayer.Inaddition,afewexperimentsaresuggestedforacheckofthepresentmodelandpicture.PACS.71.27.+aStronglycorrelatedelectronsystems–71.20.-bElectrondensityofstates–75.10.-bGeneraltheoryandmodelsofmagneticorderingarXiv:cond-mat/0210369v1[cond-mat.mtrl-sci]17Oct20021Introduction

6、pastdecades,especiallyafterthediscoveriesofthehigh-temperaturesuperconductingcupratesandthecolossalThephasediagramsoftransition-metaloxides(TMOs)magnetoresistance(CMR)manganites.Agreatnumberofconcerningtheircrystalstructures,electronic/magneticexperimentalandtheoreticalst

7、udieshaveexploitedrichandtransportpropertiesdrewveryextensiveattentioninaphysics[1],whichnotonlyleadsonetounderstandingPresentaddress:Fritz-Haber-InstitutderMax-Planck-(althoughimcompletesofar)ofthenatureandoriginofGesellschaft,Faradayweg4-6,D-14195Berlin,Germany2HuaWu:Ph

8、aseevolutionoflayeredcobaltoxidesversusvaryingcorrugationofthecobalt-oxygenbasalplanetheirfascin