Near-infrared absorption of MgF2Fe2

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1、SolidStateCommunications,Vol.14,pp.907—909,1974.PergamonPress.PrintedinGreatBritainNEAR-INFRAREDABSORPTIONOFMgF2:Fe2’U.DUrrandR.WeberPhysikalischesInstitutderUniversitatStuttgart(Teilinstitut2),W-Germany(Received16October1973byM.Cw~Iona)ThemultiphononsidebandofthespinallowedtransitionIT2~:A1—2>-‘

2、IE,:B3—2>withinthe3d6orbitalofFe24inD2hsymmetrywasanalyzedwithrespecttotheonephononabsorptionanddensityofstatesofthecoupledphononmodes.Temperaturedependenceofthezero-phononlineshows,thattheaxialanisotropyoftheS=2spinmultipletintheexcitedB3stateisabout0.9cnf’.THENEARinfrared(NIR)absorptionofFe24is

3、due~Fe25T—~‘Etotransitionswithinthefully-split3d6orbitalquintet.T~6K-polThesitesymmetryoftheFe24impurityinMgF2isD2h.ThisorbitalsplittingofFe2incrystal-fieldsofD2hsymmetrywasinvestigatedbyseveralauthorsindif-ferentcrystalsofrutilestructure.~3SoitisnowestablishedthattheorbitalgroundstatehasA1—symme

4、try.Thespinallowedtransitionfromthisground~02state,IT2,:A—2>totheexcitedEg:Bi—2>stateisaccompaniedbyamultiphononsidebandwhichis/‘structuredatlowtemperature.TheanalysisoftheIIsidebandleadstothedensityofthecoupledphonon73Q~Ø5~910097~statesofMgF2.Thereisverylittleinformationabout—.Wov.rumber(cm-‘)th

5、ephonondensityofstatesinMgF2.‘FromFIRFIG.1.Absorptionspectrumandone-phononportionmeasurementsweknowthezero-fieldsplittingoftheMgF2:Fe24.S=2spinmultipletoftheA1-orbitalgroundstateofFe2’inMgF2.~SoweareabletogetinformationaboutthesplittingofthespinmultipletintheexcitedThestructureonthesidebandhasadi

6、stanceofaboutB3-statebyvaryingthetemperatureinourexperiments.100cm~,315crn~and380cm~fromthezero-phononline(Fig.1).TheseabsorptionsareinducedbyAtroomtemperaturethespectrumconsistsofthemagneticvectoroftheincidentlightperpendiculartwobroad,almostunpolarizedbandscentredat9750tothec-axis.Ina-polarizat

7、ionnoadditionalstructurecm~and10420cm’.asexpectedfromtheTanabe—wasseen.Between6Kand59KthestructureontheSuganodiagramoftheFe2’orbitalsplittingincubicmultiphononsidebandwashesoutandtheintensitycrystalfield,6thecenterofgr