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1、LakeOntarioFePtNanomaterialsforFePtNanomaterialsforFutureMagneticDataFutureMagneticDataStorageStorageHaoZengHaoZengLakeErieDepartmentofPhysics,DepartmentofPhysics,UniversityatBuffaloUniversityatBuffalo--SUNYSUNYSummerSchoolofAdvancedFunctionalMaterials20
2、06Shenyang,China,July6,2006What’sEnablingGoogleEarth?200TBofHardDiskDrives92%ofnewinformationstoredonmagneticmedia!“Moore'sLaw”forDataStorage?HardDiskDriveTechnologyNSSNNSSNNSSNNSSNR∝10log(N)CoherentRotation-StonerWohlfarthModelH2.52.01.5HM1.0ϕθsEB0.5E0.
3、0Easyaxis-0.5-1.0-1.52sincos()ϕ=180°E=KVϑ−MVHϕ−ϑ-2.0s-2.5050100150200SettingE=0,θBOnegetH=2K/McsB.D.Cullity,IntroductiontoMagnetismandMagneticMaterialsSuperparamagnetismFMMrMsKV>>kTMagneticreversalisthermallyactivated,Hctheprobabilityofcrossingovertheene
4、rgybarrier-∆E/kT1/τ=f0e∆E=kTln(f0τ)Msf–attemptingfrequency~109Hz,τ–measurement0time~100s∆E=25kTMsKV<25kT2Ku25kBT1/2H=[1−()]cSPMKVsu25kTBV=,100sMsBKu'60kBTVB=10yearKuFightingSPLimit-AdvancedRecordingSchemesAFCmediaRuSNR∝Mtr∝(d-d)12V∝(d+d)eff12Perpendicula
5、rrecording∑Packmoredata-samevolumewithsmallerbitsize∑StabilizesstoredbitsHighKMediaMaterialsuD.Welleretal.,IEEETrans.Magn.vol36,No1,January2000,p.10-15FePt–TheHardestMagnet5nm,4.5KT.Shimaetal.,Appl.Phys.Lett.85,2571(2004)ThermallyAssistedRecordingLowerth
6、eenergybarrierforreversalbylaserheatingPRB72,172410,2005OriginofMagnetocrystallineAnisotropyofFePt¾Originofanisotropyisspin-orbitcoupling¾Fehasrelativelymoderatespin-orbitinteractions.MAEisverysmallinthebulkFe.¾Pthasverylargespin-orbitcouplingconstant,bu
7、thasnomagneticmomentinpureform.¾FePtgetsthebestoftwoworlds:Fehaslargemagneticmoment,andinducessizablemagneticmomentonPt(0.4µ).Ptprovidesspin-orbitBinteractions.BecauseofthesetheanisotropyisnotsingleioninoriginanddependsontheinteractionbetweenFeandPt.Anis
8、otropyCalculationshardeasy∆E=E−EaniseecEF1−1=ImdETr[1+∆tT]∫0aπ−∞=∑Eijij∆tIsSOperturbationandT0isascatteringT-matrixdescribinginteractionsL1FePtThinFilmsfor0MagneticRecordingMediaR.F.C.Farrow,D.Weller,R.F.Marks,andM.F.Toney
