材料物理材料磁性性质精选文档.ppt

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1、材料物理课件材料磁性性质本讲稿第一页，共三十六页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 本讲稿第二页，共三十六页II,Magnetic momentTheconceptofmagneticmomentisthesta

2、rtingpointwhendiscussingthebehaviourofmagneticmaterialswithinafield.Ifyouplaceabarmagnetinafieldthenitwillexperienceatorqueormomenttendingtoalignitsaxisinthedirectionofthefield.Acompassneedlebehavesthesame.Thistorqueincreaseswiththestrengthofthepolesandtheirdistanceapart.Sothevalueofmagneticmomentte

3、llsyou,ineffect,howbigamagnetyouhave.Itisalsowellknownthatacurrentcarryingloopinafieldalsoexperiencesatorque(electricmotorsrelyonthiseffect).Herethetorque,increaseswiththecurrent,i,andtheareaoftheloop,A.istheanglemadebetweentheaxisoftheloopnormaltoitsplaneandthefielddirection.=BiAsin=Bmsin本讲稿第三页，共三十

4、六页Diamagnetic materials arethosewhoseatomshaveonlypaired electrons.III,Diamagnetic and paramagnetic materialsParamagnetic materials are those whose atioms have unpaired electrons and has permanentmagneticmoments.Althoughparamagneticsubstanceslikeoxygen,tin,aluminiumandcoppersulphateareattractedtoama

5、gnettheeffectisalmostasfeebleasdiamagnetism.Thereasonisthatthepermanentmomentsarecontinuallyknockedoutofalignmentwiththefieldbythermalvibration,atroomtemperaturesanyway(liquidoxygenat-183Ccanbepulledaboutbyastrongmagnet).本讲稿第四页，共三十六页IV,Ferromagnetic materialsThemostimportantclassofmagneticmaterialsi

6、stheferromagnets:iron,nickel,cobaltandmanganese,ortheircompounds(andafewmoreexoticonesaswell).Themagnetizationcurvelooksverydifferenttothatofadiamagneticorparamagneticmaterial.本讲稿第五页，共三十六页V,Hysteresis loop本讲稿第六页，共三十六页Memory devices本讲稿第七页，共三十六页OutlineBackgroundSemiconductorConventionalmemorytechnolog

7、iesEmergingmemorytechnologies本讲稿第八页，共三十六页1 Magnetic MemoryMechanism:MainapplicationsTapeDisketteMagneticdrumMagneticMemorymaterials:-Fe2O3,CrO2,Fe-CoetalRead/writeheads本讲稿第九页，共三十六页2 Optical MemoryDVD-RWDVDCDApplications:Opticalstoragematerials:PC、PMMA、Epoxyetal.Mechanism:Advantage：lowprice,highstora

8、gedensity;disadvantagelowaccess,largebox本讲稿第十页，共三十六页Mainapplication:3 Semiconductor memoryBasedonsemiconductordevices；Advantage:fastaccess,highdatastorage,lowpower；CachememoryStackedmemoryFlashmemory本讲稿第十一页，共三十六页Comparison of memory technologiesOptical MemoriesMagnetic DisksMagnetic TapesMagnetic Bu

9、bble 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本讲稿第十二页，共三十六页Semiconductor memories CellarrayPeripheralcircuitI/Ounitcircuit2m+n+k-1本讲稿第十三页，共三十六页Categories of Semiconductor memories 本讲

10、稿第十四页，共三十六页Memory technologies Primarycategoriesofelectricalmemory:RAM,ROMandFlashNonvolatile:aftertransitionfromOFFstatetoONstate,deviceremainedinthisstateevenafterturningoffthepower.Randomaccessmemory(RAM):Thechargecanberefreshedfrequently.informationislostwhenthepowerremovedfromthedevice.(DRAM,SR

11、AM)Readonlymemory(ROM):Informationisnotlostwhenthepowerisswitchedoff,butthechargestoredinchipcantberefreshed.Flash:Thechargecanberefreshedfrequently,andinformationisnotlostwhenthepowerisswitchedoff.本讲稿第十五页，共三十六页DRAMThepresenceofachargerepresentsthelogicalvalue“1”anditsabsencethelogicalvalue“0”Parasi

12、ticcapacitance本讲稿第十六页，共三十六页DRAM write and read operationwriteread本讲稿第十七页，共三十六页ROM MaskROMPROMEPROMEEPROM(Flash)本讲稿第十八页，共三十六页Flash DielectricTunnel oxideMOSFET+FloatingGateThresholdshiftduetotheelectriccharge本讲稿第十九页，共三十六页MOSFET GDSDSGMetal-oxide-semiconductor field effect transistor本讲稿第二十页，共三十六页Flash

13、 write/erase/read operation Applyvoltagetocontrolgate(CG)e-tunnelingoccursfromchanneltoFGApplyvoltagetosourcee-transferoccursfromFGtosourceApplyvoltagetoCG.Ife-presentinFG,noconductionbetweenSandD.Ife-isabsent,conductionhappens.本讲稿第二十一页，共三十六页NAND&NOR FlashNANDFlash:erasedandprogrammedblock-wise.NORF

14、lash:erasedandprogrammedbyte-wise.本讲稿第二十二页，共三十六页Performance and requirements Fast accessNon-volatilityUnlimited R/W cyclesLow powerWide temperature rangeLow cost本讲稿第二十三页，共三十六页Emerging memoryFeRAMOrganicMemoryNano-CrystalFloating-GateFlashMemoryPhaseChangeMemoryNRAM本讲稿第二十四页，共三十六页FerroelectricunitHyst

15、eresiscurveTwo states of polarization under applied field can correspond to a stored“0”or“1”RemnantpolarizationCoercivefieldFerroelectric memory(FeRAM)本讲稿第二十五页，共三十六页FeRAM(capacitor)Plateline(PL)has a variable voltage level to enable the switching of the polarization of the ferroelectric capacitor.1T

16、-1C本讲稿第二十六页，共三十六页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,

17、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.本讲稿第二十七页，共三十六页FeFET(polarization)FeFET is in principle a MOSFET transistor whose gate dielectric is ferroelectric.Advantage:re

18、adingoperationisnondestructive.Disadvantage:retentiontimeisveryshorttononvolatilememory.本讲稿第二十八页，共三十六页Electrical bistability:Organic electric bistable devices Aphenomenonexhibittwokindsofdifferentstableconductivestatebyapplyingappropriatevoltage.TypicalI-VcharacteristicsSilicon memory:encode“0”and“1

19、”as the amount of charge stored in device cell Organic memory:store date based on high&low conductivity response to applied voltage本讲稿第二十九页，共三十六页Device structuresCross-BarsShadow mask本讲稿第三十页，共三十六页Device configurationsPolyanilinenanofiberGoldnanoparticlesOrganic/nanoparticlessystemMetal complex Donor

20、AcceptorDonor-Acceptorsystem本讲稿第三十一页，共三十六页Performance and Characterization ON/OFFcurrentratioWrite-read-erasecyclesSwitchingtimeRetentionability本讲稿第三十二页，共三十六页Nano-crystal floating-gate memoryOxidegatetoothinLeakagepathCauseelectronstoredtoleakoutHow to alleviate the scaling limitation?usethinnertunn

21、eloxideswithoutsacrificingnonvolatilityoxidethicknessoperatingvoltageoperatingspeedsDielectricTunnel oxide本讲稿第三十三页，共三十六页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本讲稿第三十四页，共三十六页Carbon nanotube memory本讲稿第三十五页，共三十六页Thanksforyourattention!本讲稿第三十六页，共三十六页