磁记录材料PPT课件

1、1第二讲第二讲磁记录材料磁记录材料 2 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

2、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铁磁性反铁磁性亚铁磁性亚铁磁性5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()()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

3、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 6 history of magnetic recording7oberlin smith diagram, 18888valdemar poulsen, 18989fritz pfleumer, 1928basf magnet

4、ic tapefrom ritter, 198810aeg magnetophon, 1935 11the categories and structures of hard disk12disc drives today cover the widest range of users and systems everhandheldgamingdvrnotebookdesktopenterprise12 gb750 gb160 gb73 gb 300 gb750 gb750 gblow-cost, high-capacity, disk drives are enabling new dev

5、ices, resulting in rapid growth of the storage industry and the emergence of new industries. e.g. apple ipod, pvrs, x-box, automobile navigation systems, digital video cameras, etc.1314read/write heads1516applications in data storage writing headsheads used for writing bits of information onto a spi

6、nning 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

7、 permanently magnetized in a direction (north or south) determined by the writing field. storage media exploit phenomenon d. 17writing heads and reading heads18figure 1: a writing head19figure 2:writing data on astorage medium. 20figure 3:reading data from astorage medium21figure 4:integrated write-

8、read head2223tgmr/gmr reader materialstop shieldmagnetmagnetflafm/saf/rlbottom shieldinsulatorcurrentflowelectronflowflrltunnelingbarrierflux from the media rotates reader free layer magnetization thus changing spin polarized electron tunneling conduction.mediafieldoutputvoltagefl-rlfl-rlfllinearran

9、geoperate in the linear range of transfer function.sensitivity (slope)is determined by tmr alternate barrier tgmr (mgo) improved amplitude, and lower ra potential to extend tgmr reader to area density current problem maintaining soft magnetic property of free layer, while keeping high dr/r and low r

10、a. ccp design (current confined path) a discontinuous oxide buried in metal higher dr/r and ra as compared to cpp spin value potential to use for area density of 400 600gb/in2. current problem reducing variation of ra, and dr/r, and increasing dr/r. cpp spin valve with metal or half metal spacer cou

11、ld offer better reliability, and snr at very high ktpi potential to use for area density of 600gb/in2 and behind current problem concept not proven, and processing half metals at temperature magnetic head can tolerate difficultafmpinned layerruref. layerfree layerafmpinned layerruref. layercufree la

12、yerafmpinned layerruref. layermgofree layerreader development approaches24storage media 25the first pc hard disks typically held 16 sectors per track, 20 concentric tracks todays hard disks can have thousands of sectors in a single track2627this illustration gives you some idea of just how small the

13、 flying height of a modern hard disk is 28overview of magnetic recording media 29 before 1985: fe2o3 medium, ferrite ring head (10mbin-2)1980: 1st thin film read head, continuous magnetic thin film with high hc, small (25% cgr);1990: 1st mr read head, decreasing thickness and, in turn, the transitio

14、n 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 recording30outlinet recording overview longitudinal recording perpendicular recording heat assiste

15、d magnetic recording bit patterned media. 31 magnetic recording traditional longitudinal recording is approaching to its limit (100 gbit in-2 is achieved ). (2) perpendicular recording offers about 610gbit/in2 ,2008 (3) the next big challenge is 1 tbit in-2 for recording industry. the possible model

16、s : pattern media; high ku media (hamr); stt (spin torque transfer) ram. (1) 32areal density growthsingle particle superparamagnetic limit (estimated)charaps limit (broken) late 1990s super paramagnetic limit demonstrated through modeling longitudinal recording reaching areal density limits longitud

17、inal 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+bpm3320nm20nm20nmphysical grain

18、 size below 10 nmmagnetic media evolution341955-1985: -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. snrlog10(

19、n) therefore higher densities require smaller grainsthe smaller bits have a higher probability of flipping and the data is unstabletbkvukef01high areal density means small volumeacceptable considered is 6040tktkvkbbusuper paramagnetic limit35high recording density hd 4 m need high hc to overcome hd

20、high recording density hd 0 high hc is not necessary reasons to use pmr36 advantages of pa recording: a. high orientation ratiob. lower media noise ( smaller)c. increase of signal and thermal stabilityd. writing field large 37application 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

21、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。38limits on conventional perpendicular recording 6040tktkvkbbutbkvukef01write-abil

22、itythermal stabilitysnr (grain size)large field or low anisotropylarge grains or high anisotropysmall bits requires small grains)(log10nsnr392468101214020406080100120140cocrpthamrpmrperpendicular media candidatescopt3fepdco/pdco3ptco/ptmnalfe14nd2bfeptcopt hk (koe)dp (nm)smco510 nmhama (heat assiste

23、d magnetic recording)temperaturecoercivity, hchw limitrt40magnetic 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.41temperaturecoercivity, hchw limit

24、rt42j. p. wang, nat. mater. 4, 191 (2005)new routine tilted media43new routine bit patterned media lithography vs. self organizationlithographically definedmajor 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/