磁记录材料PPT课件.ppt

第二讲第二讲磁记录材料磁记录材料  History of magnetism•  　　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是磁的故乡司南模型司南模型 •         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抗磁性顺磁性顺磁性铁磁性铁磁性反反铁铁磁磁性性亚铁磁性亚铁磁性生物磁现象生物磁现象生物磁现象生物磁现象 核磁共振层析成像核磁共振层析成像 心磁图和脑磁图心磁图和脑磁图 鸽子回家和海龟回游鸽子回家和海龟回游 磁性细菌的磁导航磁性细菌的磁导航地球磁现象地球磁现象地球磁场的变化和应用地球磁场的变化和应用 地球磁场的反向地球磁场的反向 地磁与大陆漂移及海底扩张地磁与大陆漂移及海底扩张 地球磁场与极光地球磁场与极光 地球磁场的起源地球磁场的起源 宇宙磁现象宇宙磁现象太阳磁场与太阳黑子太阳磁场与太阳黑子 阿尔法阿尔法( (αα) )磁谱仪空间探测磁谱仪空间探测 “阿波罗阿波罗”飞船测月磁飞船测月磁 磁场与空间气象学磁场与空间气象学 脉冲星与超强磁场脉冲星与超强磁场 原子核与基本粒子磁现象原子核与基本粒子磁现象电子磁距和中子磁距电子磁距和中子磁距 核磁共振与物质结构研究核磁共振与物质结构研究 穆斯堡尔效应与磁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磁致冷创造最低温度记录 核铁磁性和核反铁磁性核铁磁性和核反铁磁性 磁磁性性无无处处不不在在  History of magnetic recordingOberlin Smith diagram, 1888Valdemar Poulsen,  1898Fritz Pfleumer, 1928•BASF magnetic tapefrom Ritter, 1988AEG Magnetophon, 1935 The categories and structures of hard diskDisc Drives Today Cover the Widest Range of Users and Systems EverHandheldGamingDVRNotebookDesktopEnterprise12 GB12 GB750 GB750 GB160 GB160 GB73 GB73 GB 300 GB300 GB750 GB750 GB750 GB750 GBLow-cost, high-capacity, disk drives are enabling new devices, resulting in rapid growth of the storage industry and the emergence of new industries. e.g. Apple iPod, PVR’s, X-Box, automobile navigation systems, digital video cameras, etc.Read/write headsApplications in Data Storage•Writing HeadsHeads used for writing bits of information onto a spinning magnetic disk depend on phenomena A and B to produce and control strong magnetic fields. •Reading HeadsReading heads depend on phenomena A, B, and C, and are sensitive to the residual magnetic fields of magnetized storage media (D). •Storage Media (e.g., computer disks)Magnetic storage media are permanently magnetized in a direction (North or South) determined by the writing field. Storage media exploit phenomenon D. Writing Heads and Reading HeadsFIGURE 1: A WRITING HEADFIGURE 2:WRITING DATA ON ASTORAGE MEDIUM. FIGURE 3:READING DATA FROM ASTORAGE MEDIUMFIGURE 4:INTEGRATED WRITE-READ HEADTGMR/GMR Reader MaterialsTop ShieldMagnetMagnetFLAFM/SAF/RLBottom ShieldInsulatorCurrentFlowElectronFlowFLRLTunnelingBarrierFlux from the media rotates reader free layer magnetization thus changing spin polarized electron tunneling conduction.MediaFieldOutputVoltageFL-RLFL-RLFLLinearRangeOperate in the linear range of transfer function.Sensitivity (slope)is determined by TMRØAlternate Barrier TGMR (MgO)ØImproved amplitude, and lower RA ØPotential to extend TGMR reader to area density ØCurrent problem – Maintaining soft magnetic property of free layer, while keeping high DR/R and low RA.ØCCP Design (current confined path)ØA discontinuous oxide buried in metalØHigher DR/R and RA as compared to CPP Spin ValueØPotential to use for area density of 400~ 600Gb/In2.ØCurrent problem – Reducing variation of RA, and DR/R, and increasing DR/R.ØCPP Spin Valve With Metal or Half Metal SpacerØCould offer better reliability, and SNR at very high KTPIØ Potential to use for area density of 600Gb/In2 and behindØCurrent problem – Concept not proven, and processing half metals at temperature magnetic head can tolerate difficultAFMPinned LayerRuRef. LayerFree LayerAFMPinned LayerRuRef. LayerCuFree LayerAFMPinned LayerRuRef. LayerMgOFree LayerReader Development ApproachesStorage Media The first PC hard disks typically held 16 sectors per track, 20 concentric tracks Today's hard disks can have thousands of sectors in a single trackThis illustration gives you some idea of just how small the flying height of a modern hard disk is Overview of magnetic recording media  Before 1985: γFe2O3 medium, Ferrite ring head (～10Mbin-2)1980: 1st thin film read head, continuous magnetic thin film with high Hc, small α(25% CGR);1990: 1st MR read head, decreasing thickness and, in turn, the transition distance (80% CGR);1997: 1st GMR read head (100% CGR);2000: 1st AFM medium, increasing the effective volume.2006: 1st TMR head for 80-100 Gbit in-2 perpendicular recording The develop of the magnetic recordingOutlinetRecording Overview§Longitudinal Recording§Perpendicular Recording§Heat Assisted Magnetic Recording§Bit Patterned Media.  Magnetic Recording (1) Traditional longitudinal recording is approaching to(2) its limit (100 Gbit in-2 is achieved ).(3)(2) perpendicular recording offers about 610Gbit/in2 ,2008(4) (5)(3) the next big challenge is 1 Tbit in-2 for recording (6) industry. (7) The possible models : pattern media; high Ku media (8) (HAMR); STT (Spin torque transfer) – RAM.(9) (10) Areal Density GrowthSingle particle superparamagnetic limit (estimated)Charap’s limit (broken)–Late 1990s – super paramagnetic limit demonstrated through modeling–Longitudinal recording reaching areal density limits –Longitudinal anti-ferromagnetic recording (AFC)–Perpendicular expected to extend to 0.5-1 Tb/in2–Additional innovations required at that point•heat-assisted recording (HAMR)•bit patterned media (BPM) recording•Areal Density CAGR 40%•Transfer Rate CAGR 20%PerpendicularHAMRHAMR+BPMPhysical grain size below 10 nmMagnetic Media EvolutionMagnetic Media Evolution1955-1985: -Fe2O3 particles were dispersed in a polymer blinder and spin-coated on substrates of Al-Mg with an anodized aluminum oxide layer. Thin film disk technology started after 1985.To preserve SNR, number of grains in a bit must be constant. SNR~log10(N) Therefore higher densities require smaller grainsThe smaller bits have a higher probability of flipping and the data is unstableHigh areal density means small volumeSuper paramagnetic limitSuper paramagnetic limitHigh recording density Hd 4 M Need high Hc to overcome Hd High recording density Hd 0 High Hc is NOT necessary Reasons to use PMRReasons to use PMR Advantages of PA recording: a. high orientation ratiob. lower media noise (α smaller)c. increase of signal and thermal stabilityd. writing field large Application of the perpendicular media•2004年，东芝成为世界首个将垂直磁记录技术应用于商业硬盘的厂商。

垂直磁记录自1977年其原理提出之后，直到约30年后的2004年采用垂直磁记录方式的硬盘才首次亮相 •日立公司表示，他们2005年4月实现230 Gbit/in2，2006年9月实现345 Gbit/in2， 2008年08月04日 他们创造了垂直磁记录密度的新纪录，达到了610Gbit/in2但是由于目前垂直磁记录技术中使用的连续薄膜介质终将会达到一个密度极限，因此以后还会发展其他技术继续提高容量密度，例如离散磁道、热辅助记录等等Limits on conventional perpendicular recordingWrite-abilityThermal StabilitySNR (grain size)Large field or low anisotropyLarge grains or high anisotropySmall bits requires small grainsSmCo510 nmHAMAHAMA (Heat Assisted Magnetic Recording) (Heat Assisted Magnetic Recording)TemperatureCoercivity, HcHw limitRTMagnetic domains oriented in the direction of travel of the head.Longitudinal RecordingPerpendicular RecordingSoft underlayer “mirrors” write head and makes it possible to write domains much closer together.TemperatureCoercivity, HcHw limitRTJ. P. Wang, Nat. Mater. 4, 191 (2005)New routine ——New routine ——Tilted mediaTilted mediaNew routine —— Bit Patterned Media Lithography vs. Self OrganizationLithographically Defined•Major obstacle is finding low cost means of making mediaDirect E-Beam Write or Di-Block Co-PolymerIdea:Use Pattern Assisted Assembly to establish circumferential tracks on discsFePt Self-Organizing Media130 nm6 nm FePt particles“9 Tb/in2“ ~mmES, ECC and graded mediaAdvantages of ECC media:• Lower switching field : enhance Writability• Dynamical tilting reversal : eliminates Noise• Higher Ku hard layer: enhance Thermal stabilityHapplHard layer (high Hk) provides the thermal stabilitySoft layer (low Hk)help switch the hard layerInterfacesharpgradedDomain wall nucleation, compression and de-pinning process at the hard/soft composite interface significantly reduces switching field.Domain wallHigh HkLow HkHexcR.H. Victora, IEEE Trans. Magn. 41, 537 (2005);D. Suess, Appl. Phys. Lett. 87, 012504 (2005);D. Suess, Appl. Phys. Lett. 89, 113105 (2006). 软磁/硬磁复合介质降低矫顽力，保持降低矫顽力，保持/提高热稳定性，提高热稳定性，解决了超高密度垂直磁记录介质的三难问解决了超高密度垂直磁记录介质的三难问题。

题习题•1、谈谈对磁记录薄膜材料的认识谈谈对磁记录薄膜材料的认识•2、提高硬盘盘片的记录密度有哪些途径？、提高硬盘盘片的记录密度有哪些途径？•3. 为什么要用软磁硬磁交换耦合薄膜？为什么要用软磁硬磁交换耦合薄膜？。