Applications: Information Storage Laurent Ranno Laboratoire Louis - PowerPoint PPT Presentation

Up-to-date TAPE Example (EMTEC 2003) Tape 1/2 inch (12.5 mm) 1GB 417 m long thickness : polyester (11.6 microns, total 13.7 microns) particles : CrO 2 coercive field : 52 mTesla (+/- 5%) 20 GB 300 m long Iron particles coercitif field : 160 mTesla +/- 5% Bit aspect 270 nm 100 GB 600 m (thickness 9 microns) fine particles (iron ?) 27.5 µ m coercive field : 185 mT track/inch : 923 (27.5 micron) bit/inch : 93000 (270 nm) Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Up-to-date TAPE Example (EMTEC 2003) Tape 1/2 inch (12.5 mm) (update : EMTEC bankrupt) 1GB 417 m long thickness : polyester (11.6 microns, total 13.7 microns) particles : CrO 2 coercive field : 52 mTesla (+/- 5%) 20 GB 300 m long Iron particles coercitif field : 160 mTesla +/- 5% Bit aspect 270 nm 100 GB 600 m (thickness 9 microns) fine particles (iron ?) 27.5 µ m coercive field : 185 mT track/inch : 923 (27.5 micron) bit/inch : 93000 (270 nm) Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Media : Continuous Media Beyond particle media smaller particle --> continuous granular media better materials --> cobalt based Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

� Magnetic Recording Media : Transition Width M x x Longitudinal Media x 2a Let us suppose that M does not depend on thickness M 2 x = M x s The transition width is 2a ( ) arctan x a π dM x M ( ) 2 1 The density of « magnetic » charges is : ρ = − = − = − div M s π ⋅ dx a x 2 + 1 a 2 - - ------ - - - - ------ - - - - ------ - - x x Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Media : Transition Width ρ ⋅ - - ------ - - r dV t � - - ------ - - 1 - - ------ - - = H d � - - ------ - - - - ------ - - ��� - - ------ - - π r - - ------ - - 3 4 x 0 x M t a 2 = − H Bit width infinite � s d π ⋅ x a 2 + 2D charge + 1 a 2 M t 2 1 ≤ ≤ H s H Maximum Demag field d c π ⋅ a 2 M t M t M t , ( in fact) As small as possible ≥ π a s s r ⋅ H H As large as possible c c Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Media : Transition Width Thin film media M r t As small as possible Small magnetisation Signal amplitude will also decrease !!!! H As large as possible Hard magnetic materials c The write field should be larger than H c !!! Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Media : Continuous Media Need to reduce M r t Lubricant to increase H C Carbon overcoat CoCrM / Cr (M=Ta, Pt) Magnetic layer 30-50 nm Cr underlayer Substrate Thin film media Exchange coupling → transition noise Has been limited by : • Physical grain segregation (process / underlayer effects) • Compositional segregation Cr-rich Co-rich Max. storage density ≈ 30 Gbits/in 2 Min. bit area ≈ 2 x10 -2 µ m 2 Applications : disk drives Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Media : A physical limit : Superparamagnetism Superparamagnetism Remanent state is bistable lower limit to the size of a stable ferromagnetic particle if anisotropy energy < thermal energy i.e. K V < kT for data storage want τ τ > 10 years τ τ K V / kT > 60 i.e. must have K υ υ υ υ at 300 K φ min K 1 π 0 (MJ/m 3 ) (nm) Uniaxial system Fe 0.05 20 thermal relaxation time, τ τ τ τ Co 0.5 8 τ 0 exp(K V / kT ) τ τ = τ τ τ τ τ Nd 2 Fe 14 B 5 4 SmCo 5 17 2 1/ τ τ τ 0 is the attempt frequency ( τ τ τ 0 ≈ 10 -9 s) τ τ Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Media : Enhanced Continuous Media CoCrPt - - - AFC coupled media - - - + + Ru (0.6nm) M r .t becomes M r .t 1 -M r .t 2 RKKY AF coupled bilayer Co/Ru/Co Fullerton et al. APL 2001 Total M r .t decreases : less sensitive to demagnetising fields but less signal also Total M r .t decreases : but V does not, so K.V can be maintained Max. storage density ≈ 45 Gbits/in 2 106 Gbit/in 2 in 2001 (Fujitsu) Min. bit area ≈ 10 -2 µ m 2 130 Gbit/in 2 in 2002 (Read-Rite) Applications : Ultra High Density Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

State-of-the-art longitudinal media 26.5 Gb/in 2 demonstrator M.A. Schultz et al. (Read-Rite), IEEE Trans Mag. 36 (2000)2143 CoCrPtTaB/Cr 5 nm Intermag 2002 (Seagate and Fujitsu) 100 Gbit/in 2 µ 0 Hc : 0.25 T µ 0 Hc : 0.48 T M r t : 0.4 x10 -3 emu/cm 2 M r t : 0.35 x10 -3 emu/cm 2 Film thickness : 19 nm AFC Film Average grain size : 11 nm Average grain size : 9 nm Transition parameter : 20 nm Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Media : Beyond Present Continuous Media Perpendicular recording Different aspect ratio : Decrease of demagnetising field Thicker films allowed SUL : Soft Underlayer to double the thickness The write head should now provide perpendicular fields new head design Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Media : Beyond Present Continuous Media Perpendicular recording MMM 2002 (Seagate and ReadRite) 130 and 146 Gbit/in 2 µ 0 Hc : 0.6 T M r t : 0.4 x10 -3 emu/cm 2 Fuji film ? Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

PATTERNED MEDIA GRANULAR MEDIA 10 3 -10 4 GRAINS = 1 BIT 1 GRAIN = 1 BIT granular media give also rise to media noise (not well defined transition) Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Media : Beyond Continuous Media Patterned media : How to make them ? e-beam lithography Nano-imprint self assembly + self organisation moiré arrays Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Grain Dispersion Narrowing SOMA : Self Organised Magnetic Array 45 Gbit/in 2 demo media (Seagate) Nanoparticle arrays • 8.5 nm grains • 6 nm FePt particles ≅ 0.5 σ σ σ σ area ≅ ≅ ≅ ≅ 0.1 � σ σ σ σ area ≅ ≅ ≅ S. Sun, Ch.Murray, D. Weller, L. Folks, A. Moser, Science, 287, 1989 (2000) (slide courtesy of D. Weller - Seagate) Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Co-Pt multilayers irradiated by a He + beam Change of magnetic properties Same idea with FePt L 10 phase Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Nano-imprint + RIE + Lift-off Ni + Si RIE + Co-Pt mutilayers 60 nm dot array Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic dimensions are smaller than ! semiconductor industry lithography tools 400 350 International Technology Roadmap for semiconductors 300 Node number 250 200 Magnetic Bit length 150 100 50 0 1995 2000 2005 2010 2015 Year Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

III-Heads Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Heads Stray field measurement only magnetic transition contribute M-O signal laser wavelength limit (diffraction) Solid state (resistance) electrical connection memory matrix Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Heads : inductive heads Write head = Read head ϕ ⋅ d S dB = − = − e dt dt velocity : moving media and/or moving head surface : signal proportional to coil area now floppy, VHS ... Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Heads : inductive heads Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Ferrite Head (hard disk Seagate ST251 50 MB 1990, present floppy head) MIG (Metal-in-gap) head : deposition of an iron rich alloy onto the poles to increase their magnetisation (and thus, their saturation). Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Heads : inductive heads Space Resolution = Gap Length Difficult to reduce the write gap down to submicron size From Wound coils to Thin film heads Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Heads : inductive heads Thin film head Bottom Pole (NiFe) Copper windings Top Pole (NiFe) (Read-Rite) Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Higher Magnetisation Materials to create larger magnetic fields NiFe ---> FeCo based (and soft) Presently demonstration with 2.4 Tesla materials Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Heads : MR heads Larger signal : electrical response to stray fields AMR (Anisotropic Magnetoresistance) : Ni 80 Fe 20 (permalloy) film GMR (Giant Magnetoresistance) : Fe / Cu / NiFe TMR (Tunnel Magnetoresistance ) : Fe / Al 2 O 3 /NiFe Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Heads : MR heads Dépendance Angulaire de la MR 1.5 AMR GMR 1 Work-points 0.5 0 -0.5 -1 -1.5 -150 -100 -50 0 50 100 150 Angle (°) Signal processing people want linear response Consequence for linear sensing : Angle at 45° or 90° Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

How to work 45° from current direction ? AMR sensor : Barber pole configuration Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

How to work 45° from current direction ? AMR sensor : Biasing using a second layer + current in the sensing layer Bias layer Sensor layer Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

+ - + - + - + - + - + - B � - - - Sensing current Rotation bias layer Rotation sensing layer Magnetic field Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Complete MR Head Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Heads : optical heads Read (or heat assistance) example M-O disk Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Heads : optical heads 640 MB on 3,5 in (Floppy format instead of CD-ROM) 23 ktpi (1.1 micron) 53 kbpi (480 nm) film (TbGd)(FeCo) with perpendicular anisotropy on polycarbonate substrate or glass Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

IV-Drive Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Disk Rotation : 15 000 rpm Magnetic Recording Drive : A hard disk Head-disk height : 50-15 nm Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Hard disks (2003) Hitachi (ex IBM) Seagate 147 GB (5 disks 10 heads) 180 GB (12 disks 24 heads) 30 Gb/in 2 7400 rpm 10000 rpm 586 kbpi 51 ktpi 38 GB (4 disks 8 heads) 15000 rpm 180 GB (3 disks 6 heads) 45 Gb/in 2 7600 rpm 632 kbpi 72 ktpi New generation is 80 GB/platter 250 GB HDD are in the shops Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Drive : Data transfer, coding Coding system Codage floppy disk Frequency Modulation : 1 is flux reversal + flux reversal 0 is no reversal + reversal (simple density recording) Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Drive : Data transfer, coding Better Coding system Modified Frequency Modulation 2 clock transitions /bit 1 : N R but 0 after a 1 : N N never RR 0 after a 0 : R N (present double density Recording ) Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Magnetic Recording Drive : Data transfer, coding Hard Disk Coding MF : 1.5 flux reversal /bit MFM : 0.75 flux reversal /bit RLL (Run Length Limited) 0.46 flux reversal /bit PRML (Partial Response Maximum Likelihood) increase 30% EPRML increase 20% Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

V - Future Developments Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

AMR (anisotropic magnetoresistance) heads, 1-3Gb/in 2 , 1997. Regular GMR (giant magnetoresistance) heads, 5Gb/in 2 , 1998. Synthetic anti-ferromagnetic (SAF) biased GMR heads, 6Gb/in 2 and beyond, since 1998. Anti-ferromagnetic coupled (AFC) media, since 2000 (45 Gbit/in 2 ). Seagate (2001) and Fujitsu(2002) demonstrated 100Gb/in 2 using AFC media and SAF GMR head Perpendicular recording, may achieve areal density of 500Gb/in 2 – 1000Gb/in 2 . Seagate demonstrated >100 Gb/in 2 last year. Thermal assisting magnetic recording, proposed by Seagate Research. * D. Thompson, J. Best, “The future of magnetic data storage technology”, IBM J. Res. Develop., Vol.44, No.3, 2000. Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Thermally assisted writing •Use of high anisotropy media with high coercivities limited by write head fields •Limitations may be eased by reducing the coercivity of the media during writing by local heating with a laser beam "Hybrid recording" BUT : Transition width increases if M r and H c change at different rates Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

VI - MRAM Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Smart cards : MEMORY central processing unit (CPU)+ random access memory (RAM)+ BYTES read only memory (ROM)+ mass storage (EEPROM)+ I/O hardware and an operating system. COMPUTING CAPACITY Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Why MRAM ? Remanent Magnetisation is Non Volatile Density could compete with other RAMs Physical limit to speed is < nanosecond Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Switching Field of the free layer current current Stoner-Wohlfarth astroid (coherent rotation of magnetisation) (uniaxial anisotropy) Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Motorola 1 Mbit (june 2002) 50 ns read/write cycle NEC 1 Mbit (may 2003) Cypress 256kb = 32 kB see www.cypress.com for specs Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Comparison Solid State Memories (RAM) THE COMPETITION HAS STARTED Storage DRAM SRAM Flash MRAM FeRAM PC- Mechanism RAM Date 2002 2002 2002 2004 2004 2004 Initial Size 130 nm 130 nm 150 nm 350 nm 130 nm 100nm Structure/ 1T-1C 6T 1T 1T-1C 1T-1C 1T-1C cell 20 F 2 Surface/Cell 8F 2 10F 2 10F 2 10-20F 2 6F 2 0.68 µ 2 ? 0.14 µ 2 0.16 µ 2 0.19 µ 2 0.06 µ 2 R-W time <20ns <10ns ~80ns (R) <25ns <10ns <100ns 1ms (W) Cycling Unlimited Unlimited >10 5 >10 15 >10 13 >10 13 Permanent Volatile Volatile >10 y >10 y >10 y > 10 y Flash : 12 Volt Write Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

FLASH memory Principle <5000 electrons > 30000 electrons Leakage < 1 e /day Large voltage pulse to move the charge Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Ferroelectric RAM (FeRAM) Pb(Zr x Ti 1-x )O 3 or SbBi 2 Ta 2 O 9 Condensator with a ferroelectric dielectric Bit-line Word-line P Drive-line Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Reading destroys the information Non square loop : remanence is not well defined, the access transistor is necessary Commercial FeRAM : RAMTRON : 256 kb Hynix : 4 and 8 Mb (90 ns) Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Phase Change Memory (PC-RAM) Ge 2 Sb 2 Te 5 : amorphous (resistive) crystallised 40X more conducting Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

PC-RAM : Writing - Erasing Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Millipede : mechanical storage Still a laboratory toy but very impressive prototypes Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Denser, Smaller ... (Micro-drive Hitachi 1GB) Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

The largest Guinea Pig in the World Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

68 Degrees, 40% RH Magnetic Tape Optical Disk Paper Microfilm High Quality (low lignin) Archival Quality (Silver) "Permanent" (buffered) Newspaper (high lignin) Data 8mm / Data VHS Medium-Term Film Length of Length of QIC / QIC-wide Storage: Storage: based on DDS / 4mm based on 3490/3490e CD-ROM Data D-2 Data D-3 products products WORM CD-R available in available in DLT M-O I-D1 3480 1995 1995 1 week 1 week 2 weeks 2 weeks 1 month 1 month 3 months 3 months 6 months 6 months 1 year 1 year 2 years 2 years 5 years 5 years 10 years 10 years 15 years 15 years 20 years 20 years 30 years 30 years 50 years 50 years 100 years 100 years 200 years 200 years 500 years 500 years Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

VHS-storage (helicoidal storage) �������� ����� ����� ���� ����� ������� ��� �������� �������������� ���� ������������ ���� ����������� ����������������������������������� ���������� ���������������������������������� ��������� Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Intel 1998 Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Parallel storage ������������������� ���������� ������������������������� ������������������� ����������� ��������������� ������������� Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)

Structure électronique d ’un métal ferromagnétique Métal normal Métal ferromagnétique Recording Course Brasov sept. 2003 Laurent Ranno (Lab. Louis Néel)