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1、第二讲磁记录材料Historyofmagnetism司南是我国春秋战国时代发明的一种最早的指示南北方向的指南器。中华民族很早就认识到了磁现象，古代中国在磁的发现、发明和应用上等许多方面都居于世界首位，可以说中国是磁的故乡。司南模型物质的磁性来自构成物质的原子，原子的磁性又主要来自原子中的电子。原子中电子的磁性有两个来源：一个来源是电子本身具有自旋磁矩；另一个来源是电子绕原子核作轨道运动时产生轨道磁矩。抗磁性顺磁性铁磁性反铁磁性亚铁磁性生物磁现象生物磁现象核磁共振层析成像心磁图和脑磁图鸽子回家和海龟回游磁性细菌的磁导航地球磁现象地球磁场的变化和应用地球磁场的反向地磁与大陆漂
2、移及海底扩张地球磁场与极光地球磁场的起源宇宙磁现象太阳磁场与太阳黑子阿尔法(α)磁谱仪空间探测“阿波罗”飞船测月磁磁场与空间气象学脉冲星与超强磁场原子核与基本粒子磁现象电子磁距和中子磁距核磁共振与物质结构研究穆斯堡尔效应与磁结构研究核磁致冷创造最低温度记录核铁磁性和核反铁磁性磁性无处不在HistoryofmagneticrecordingOberlinSmithdiagram,1888ValdemarPoulsen,1898FritzPfleumer,1928BASFmagnetictape fromRitter,1988AEGMagnetophon,1935Thecat
3、egoriesandstructuresofharddiskDiscDrivesTodayCovertheWidestRangeofUsersandSystemsEverHandheldGamingDVRNotebookDesktopEnterprise12GB750GB160GB73GB300GB750GB750GBLow-cost,high-capacity,diskdrivesareenablingnewdevices,resultinginrapidgrowthofthestorageindustryandtheemergenceofnewindustries.e
4、.g.AppleiPod,PVR’s,X-Box,automobilenavigationsystems,digitalvideocameras,etc.Read/writeheadsApplicationsinDataStorageWritingHeadsHeadsusedforwritingbitsofinformationontoaspinningmagneticdiskdependonphenomenaAandBtoproduceandcontrolstrongmagneticfields.ReadingHeadsReadingheadsdependonpheno
5、menaA,B,andC,andaresensitivetotheresidualmagneticfieldsofmagnetizedstoragemedia(D).StorageMedia(e.g.,computerdisks)Magneticstoragemediaarepermanentlymagnetizedinadirection(NorthorSouth)determinedbythewritingfield.StoragemediaexploitphenomenonD.WritingHeadsandReadingHeadsFIGURE1:AWRITINGHE
6、ADFIGURE2:WRITINGDATAONA STORAGEMEDIUM.FIGURE3:READINGDATAFROMA STORAGEMEDIUMFIGURE4:INTEGRATEDWRITE-READHEADTGMR/GMRReader MaterialsTopShieldMagnetMagnetFLAFM/SAF/RLBottomShieldInsulatorCurrentFlowElectronFlowFLRLTunnelingBarrierFluxfromthemediarotatesreaderfreelayermagnetizationthuschan
7、gingspinpolarizedelectrontunnelingconduction.MediaFieldOutputVoltageFL-RLFL-RLFLLinearRangeOperateinthelinearrangeoftransferfunction.Sensitivity(slope)isdeterminedbyTMRAlternateBarrierTGMR(MgO)Improvedamplitude,andlowerRAPotentialtoextendTGMRreadertoareadensityCurre
