磁記錄材料PPT課件

1、1第二講第二講磁記錄材料磁記錄材料 2 history of magnetism 司南是我國春秋戰(zhàn)國時(shí)代發(fā)明的一種最早的指示南北方向司南是我國春秋戰(zhàn)國時(shí)代發(fā)明的一種最早的指示南北方向的指南器。中華民族很早就認(rèn)識到了磁現(xiàn)象，古代中國在磁的的指南器。中華民族很早就認(rèn)識到了磁現(xiàn)象，古代中國在磁的發(fā)現(xiàn)、發(fā)明和應(yīng)用上等許多方面都居于世界首位，可以說中國發(fā)現(xiàn)、發(fā)明和應(yīng)用上等許多方面都居于世界首位，可以說中國是磁的故鄉(xiāng)。是磁的故鄉(xiāng)。司南模型司南模型 物質(zhì)的磁性來自構(gòu)成物質(zhì)的原子，原子的磁性又主要來自原子中的電子。原子中電子的磁性有兩個(gè)來源：一個(gè)來源是電子本身具有自旋磁矩；另一個(gè)來源是電子繞原子核作軌道運(yùn)動(dòng)時(shí)

2、產(chǎn)生軌道磁矩?？勾判钥勾判皂槾判皂槾判澡F磁性鐵磁性反鐵磁性反鐵磁性亞鐵磁性亞鐵磁性5生物磁現(xiàn)象生物磁現(xiàn)象生物磁現(xiàn)象生物磁現(xiàn)象 核磁共振層析成像核磁共振層析成像 心磁圖和腦磁圖心磁圖和腦磁圖 鴿子回家和海龜回游鴿子回家和海龜回游 磁性細(xì)菌的磁導(dǎo)航磁性細(xì)菌的磁導(dǎo)航地球磁現(xiàn)象地球磁現(xiàn)象地球磁場的變化和應(yīng)用地球磁場的變化和應(yīng)用 地球磁場的反向地球磁場的反向 地磁與大陸漂移及海底擴(kuò)張地磁與大陸漂移及海底擴(kuò)張 地球磁場與極光地球磁場與極光 地球磁場的起源地球磁場的起源 宇宙磁現(xiàn)象宇宙磁現(xiàn)象太陽磁場與太陽黑子太陽磁場與太陽黑子 阿爾法阿爾法()()磁譜儀空間探測磁譜儀空間探測 “阿波羅阿波羅”飛船測月磁飛船

3、測月磁 磁場與空間氣象學(xué)磁場與空間氣象學(xué) 脈沖星與超強(qiáng)磁場脈沖星與超強(qiáng)磁場 原子核與基本粒子磁現(xiàn)象原子核與基本粒子磁現(xiàn)象電子磁距和中子磁距電子磁距和中子磁距 核磁共振與物質(zhì)結(jié)構(gòu)研究核磁共振與物質(zhì)結(jié)構(gòu)研究 穆斯堡爾效應(yīng)與磁結(jié)構(gòu)研究穆斯堡爾效應(yīng)與磁結(jié)構(gòu)研究 核磁致冷創(chuàng)造最低溫度記錄核磁致冷創(chuàng)造最低溫度記錄 核鐵磁性和核反鐵磁性核鐵磁性和核反鐵磁性 磁磁性性無無處處不不在在 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，東芝成為世界首個(gè)將垂直磁記錄技術(shù)應(yīng)用于商業(yè)硬盤的廠商。垂直

21、磁記錄自1977年其原理提出之后，直到約30年后的2004年采用垂直磁記錄方式的硬盤才首次亮相。 日立公司表示，他們2005年4月實(shí)現(xiàn)230 gbit/in2，2006年9月實(shí)現(xiàn)345 gbit/in2， 2008年08月04日 他們創(chuàng)造了垂直磁記錄密度的新紀(jì)錄，達(dá)到了610gbit/in2。但是由于目前垂直磁記錄技術(shù)中使用的連續(xù)薄膜介質(zhì)終將會達(dá)到一個(gè)密度極限，因此以后還會發(fā)展其他技術(shù)繼續(xù)提高容量密度，例如離散磁道、熱輔助記錄等等。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/