材料物理材料磁性性质精选PPT.ppt
材料物理课件材料磁性性质第1页，此课件共36页哦I,Magnetization CurvesFig.MPAa)isthecurveintheabsenceofanymaterial:avacuum.Thegradientofthecurveis4.10-7whichcorrespondstothefundamentalphysicalconstant0.magneticfluxdensity:(A/m,Gs)B=0(H+M).M=mHB=H=0(1+m)H,r=/0 第2页，此课件共36页哦II,Magnetic momentTheconceptofmagneticmomentisthestartingpointwhendiscussingthebehaviourofmagneticmaterialswithinafield.Ifyouplaceabarmagnetinafieldthenitwillexperienceatorqueormomenttendingtoalignitsaxisinthedirectionofthefield.Acompassneedlebehavesthesame.Thistorqueincreaseswiththestrengthofthepolesandtheirdistanceapart.Sothevalueofmagneticmomenttellsyou,ineffect,howbigamagnetyouhave.Itisalsowellknownthatacurrentcarryingloopinafieldalsoexperiencesatorque(electricmotorsrelyonthiseffect).Herethetorque,increaseswiththecurrent,i,andtheareaoftheloop,A.istheanglemadebetweentheaxisoftheloopnormaltoitsplaneandthefielddirection.=BiAsin=Bmsin第3页，此课件共36页哦Diamagnetic materials arethosewhoseatomshaveonlypaired electrons.III,Diamagnetic and paramagnetic materialsParamagnetic materials are those whose atioms have unpaired electrons and has permanentmagneticmoments.Althoughparamagneticsubstanceslikeoxygen,tin,aluminiumandcoppersulphateareattractedtoamagnettheeffectisalmostasfeebleasdiamagnetism.Thereasonisthatthepermanentmomentsarecontinuallyknockedoutofalignmentwiththefieldbythermalvibration,atroomtemperaturesanyway(liquidoxygenat-183Ccanbepulledaboutbyastrongmagnet).第4页，此课件共36页哦IV,Ferromagnetic materialsThemostimportantclassofmagneticmaterialsistheferromagnets:iron,nickel,cobaltandmanganese,ortheircompounds(andafewmoreexoticonesaswell).Themagnetizationcurvelooksverydifferenttothatofadiamagneticorparamagneticmaterial.第5页，此课件共36页哦V,Hysteresis loop第6页，此课件共36页哦Memory devices第7页，此课件共36页哦OutlineBackgroundSemiconductorConventionalmemorytechnologiesEmergingmemorytechnologies第8页，此课件共36页哦1 Magnetic MemoryMechanism:MainapplicationsTapeDisketteMagneticdrumMagneticMemorymaterials:-Fe2O3,CrO2,Fe-CoetalRead/writeheads第9页，此课件共36页哦2 Optical MemoryDVD-RWDVDCDApplications:Opticalstoragematerials:PC、PMMA、Epoxyetal.Mechanism:Advantage：lowprice,highstoragedensity;disadvantagelowaccess,largebox第10页，此课件共36页哦Mainapplication:3 Semiconductor memoryBasedonsemiconductordevices；Advantage:fastaccess,highdatastorage,lowpower；CachememoryStackedmemoryFlashmemory第11页，此课件共36页哦Comparison of memory technologiesOptical MemoriesMagnetic DisksMagnetic TapesMagnetic Bubble MemoriesSemiconductor RAMsSemiconductor ROMs10010-110-210-310-410-510-610-710-810-910-1010-910-810-710-610-510-410-310-2Access timeCost per bitMain memoryCache第12页，此课件共36页哦Semiconductor memories CellarrayPeripheralcircuitI/Ounitcircuit2m+n+k-1第13页，此课件共36页哦Categories of Semiconductor memories 第14页，此课件共36页哦Memory technologies Primarycategoriesofelectricalmemory:RAM,ROMandFlashNonvolatile:aftertransitionfromOFFstatetoONstate,deviceremainedinthisstateevenafterturningoffthepower.Randomaccessmemory(RAM):Thechargecanberefreshedfrequently.informationislostwhenthepowerremovedfromthedevice.(DRAM,SRAM)Readonlymemory(ROM):Informationisnotlostwhenthepowerisswitchedoff,butthechargestoredinchipcantberefreshed.Flash:Thechargecanberefreshedfrequently,andinformationisnotlostwhenthepowerisswitchedoff.第15页，此课件共36页哦DRAMThepresenceofachargerepresentsthelogicalvalue“1”anditsabsencethelogicalvalue“0”Parasiticcapacitance第16页，此课件共36页哦DRAM write and read operationwriteread第17页，此课件共36页哦ROM MaskROMPROMEPROMEEPROM(Flash)第18页，此课件共36页哦Flash DielectricTunnel oxideMOSFET+FloatingGateThresholdshiftduetotheelectriccharge第19页，此课件共36页哦MOSFET GDSDSGMetal-oxide-semiconductor field effect transistor第20页，此课件共36页哦Flash write/erase/read operation Applyvoltagetocontrolgate(CG)e-tunnelingoccursfromchanneltoFGApplyvoltagetosourcee-transferoccursfromFGtosourceApplyvoltagetoCG.Ife-presentinFG,noconductionbetweenSandD.Ife-isabsent,conductionhappens.第21页，此课件共36页哦NAND&NOR FlashNANDFlash:erasedandprogrammedblock-wise.NORFlash:erasedandprogrammedbyte-wise.第22页，此课件共36页哦Performance and requirements Fast accessNon-volatilityUnlimited R/W cyclesLow powerWide temperature rangeLow cost第23页，此课件共36页哦Emerging memoryFeRAMOrganicMemoryNano-CrystalFloating-GateFlashMemoryPhaseChangeMemoryNRAM第24页，此课件共36页哦FerroelectricunitHysteresiscurveTwo states of polarization under applied field can correspond to a stored“0”or“1”RemnantpolarizationCoercivefieldFerroelectric memory(FeRAM)第25页，此课件共36页哦FeRAM(capacitor)Plateline(PL)has a variable voltage level to enable the switching of the polarization of the ferroelectric capacitor.1T-1C第26页，此课件共36页哦FeRAM operationTo write“1”in the cell,BL is set to VDD and PL is grounded,then a pulse is applied to activate the cell transistor.To write“o”,accomplished in the same manner but PL and BL are exchanged to reverse the polarization of Ferroelectric capacitor.Read:first BL is grounded,then it is made floating.After the cell is selected by WL,the PL voltage is raised from GND to VDD,raised voltage of BL is dependent of the polarization(data)stored in FeCAP.第27页，此课件共36页哦FeFET(polarization)FeFET is in principle a MOSFET transistor whose gate dielectric is ferroelectric.Advantage:readingoperationisnondestructive.Disadvantage:retentiontimeisveryshorttononvolatilememory.第28页，此课件共36页哦Electrical bistability:Organic electric bistable devices Aphenomenonexhibittwokindsofdifferentstableconductivestatebyapplyingappropriatevoltage.TypicalI-VcharacteristicsSilicon memory:encode“0”and“1”as the amount of charge stored in device cell Organic memory:store date based on high&low conductivity response to applied voltage第29页，此课件共36页哦Device structuresCross-BarsShadow mask第30页，此课件共36页哦Device configurationsPolyanilinenanofiberGoldnanoparticlesOrganic/nanoparticlessystemMetal complex DonorAcceptorDonor-Acceptorsystem第31页，此课件共36页哦Performance and Characterization ON/OFFcurrentratioWrite-read-erasecyclesSwitchingtimeRetentionability第32页，此课件共36页哦Nano-crystal floating-gate memoryOxidegatetoothinLeakagepathCauseelectronstoredtoleakoutHow to alleviate the scaling limitation?usethinnertunneloxideswithoutsacrificingnonvolatilityoxidethicknessoperatingvoltageoperatingspeedsDielectricTunnel oxide第33页，此课件共36页哦Phase change memoryChangethephasetocrystalline(setorconductive)andamorphous(resetorresistive)bypassing a programming current of different magnitudes(higher current,pulse current,lower current)throughmemoryelement.Material:Ge2Sb2Te5(GST)Switching:10-30nsCyclingtime:1012第34页，此课件共36页哦Carbon nanotube memory第35页，此课件共36页哦Thanksforyourattention!第36页，此课件共36页哦
