magnetic recording - italian school of magnetism 2012

Magnetic Recording

[email protected] ITALIAN SCHOOL OF MAGNETISM | Pavia | February 5-10, 2012

by

Gaspare Varvaro

Istituto di Struttura della Materia – CNRNanostructured Magnetic Materials Group

Outline

Brief History of Magnetic Recording

Hard Disk Drives− General Aspects (Longitudinal Recording)

Slide [email protected] ITALIAN SCHOOL OF MAGNETISM | Pavia | February 5-10, 2012

− General Aspects (Longitudinal Recording)− Perpendicular Recording− Future Perspectives

Final Remarks

From Telegraphone to Hard Disk Drive

1898 Valdmer Poulsen invented magnetic audio recorder (Telegraphone)

ELECTROMAGNET

FINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES


WOUNDED WIRE

WRITING PROCESS

SOUND

I(t)

H(t) Mr(x)

B(t)

I(t)

SOUND

READING PROCESS

Mr(x)

ANALOG RECORDING

Mr Mr

xH

t

I


1930s AEG and BASH developed magnetic audio-tape recorder (Magnetophone)

From Telegraphone to Hard Disk DriveFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES


Write/Read HeadRing inductive head

Recording MediumAcetate tape coated with a layer of γ-Fe2O3

particles



1956 AMPEX introduced magnetic video recording.

1962 Philips invented compact cassette.

1976 Panasonic invented VHS system.






1956 AMPEX introduced magnetic video recording.

1962 Philips invented compact cassette.

1976 Panasonic invented VHS system.

1956 IBM invented the first Hard Disk DriveRAMAC – Random Access Memory of Accounting and Control


• Digital recording (0s and 1s)

• Multiple read/erase cycle

• Random access capability

• Capacity = 5 MB

• 50 Magnetic Disk (diameter = 24 in)

• Recording density = 2Kb/in2

1956 RAMAC – Random Access Memory of Accounting and Control

Areal Density EvolutionFINAL REMARKS

DISK MEDIUM

SPINDLE

HISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

1

10

100

1000

10000

100000 10 Tb/in2

2006 Perp. Media TMR Read Head

2001 AFC Media

1997 GMR Read Head

1 Tb/in2

100 Gb/in2

1 Gb/in2

Are

al D

ensi

ty

[Gb/

in2 ]

BPM,

High Ku

Materials,HAMR, ESM,

etc.

?

Longitudinal Recording Perpendicular Recording Future Perspectives

Current HDDs • Perpendicular technology

• Recording Density: 600 Gb/in2

• HDD sold in 2010: 700 million• Cost/Gb: 0.02 $

▲▲▲▲2011 DEMO

[Co/Pd]n BPM – 1T/in2

TERAMAGSTOR EU-Project


HEAD

SPINDLE

MOTOR

VOICE COIL

MOTOR

ENCODER

&DECODER

1960 1970 1980 1990 2000 2010 2020 20301E-6

1E-5

1E-4

1E-3

0.01

0.1 1990 MR Read Head

1980 Thin Film WR Head

1 Mb/in2

Are

al D

ensi

ty

Year

1956 IBM RAMAC (first HDD, 2 Kb/in2)

Longitudinal Recording

Perpendicular Recording

Areal Density EvolutionFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES Longitudinal Recording Perpendicular Recording Future Perspectives

Current HDDs • Perpendicular technology

• Recording Density: 600 Gb/in2

• HDD sold in 2010: 700 million• Cost/Gb: 0.02 $

1

10

100

1000

10000

100000 10 Tb/in2


2001 AFC Media

1997 GMR Read Head

1 Tb/in2

100 Gb/in2

1 Gb/in2

Are

al D

ensi

ty

[Gb/

in2 ]

BPM,

High Ku


etc.

?

DISK MEDIUM

SPINDLE

▲▲▲▲2011 DEMO




1960 1970 1980 1990 2000 2010 2020 20301E-6

1E-5

1E-4

1E-3

0.01

0.1 1990 MR Read Head


1 Mb/in2

Are

al D

ensi

ty

Year




HEAD

SPINDLE

MOTOR

VOICE COIL

MOTOR

ENCODER

&DECODER

Recording ProcessLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

Clock window

Writing

current

Magnetic

pattern

Writing

field

WR

ITING

PR

OC

ESS

REA

DIN

GIV


Recording head• Inductive• MR

BitRecordedtransition

Read head

Head fringe field

AREAL DENSITY (Gb/in2) = tpi x bpitpi = track/in

bpi = bit/in

Output

voltage

from head

Data read

PR

OC

ESS

Recording Medium

Write HeadLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

BitHead fringe

Ring-shapedminiature

electromagnet

1970 1980 - 2006BULK FERRITE INDUCTIVE HEAD THIN FILM INDUCTIVE HEAD

PREPARED BY PHOTOLITHOGRAPHIC PROCESSES

AREAL DENSITY (Smaller size - Higher working frequency - Higher magnetic density flux)Recordedtransition

Recording Medium

PER

PEN

DIC

ULA

RR

EC

OR

DIN

GI


fringe field

High Bs → High Hg < Bs→ High Hx > 1.5 Hsw(recording medium)

High µ → High efficiency (low I)Low Hc and Br → Low Hysteresis Losses

transition

d = 20 nm in 2006

y

x

Materialµµµµmax

(103)4ππππMs

(G)Hc

(Oe)

Fe 5 2.15 0.9

Fe49Co49V2 20 2.40 0.5

Ni50Fe50 40 1.60 0.1

Ni80Fe15Mo5 300 0.65 0.01

Read HeadLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

1970BULK FERRITE INDUCTIVE HEAD

1980THIN FILM INDUCTIVE HEAD

1997 - 2006GIANT MAGNETORESISTANCE

HEAD (GMR)

PER

PEN

DIC

ULA

R

REC

OR

DIN

G1990

ANISOTROPIC MAGNETORESISTANCE

HEAD (AMR)

AREAL DENSITY (Smaller size - Higher working frequency – Higher sensitivity)

V


MechanismElectromagnetic induction.

TrackwidthBit

length (B)


electromagnet

Recordedtransition

Recording Medium

V




1990ANISOTROPIC MAGNETORESISTANCE

HEAD (AMR)


HEAD (GMR)

PER

PEN

DIC

ULA

R

REC

OR

DIN

G


V


TrackwidthBit

length (B)


electromagnet

Recordedtransition

Recording Medium

Mechanism Electromagnetic induction.

V

V





HEAD (GMR)

PER

PEN

DIC

ULA

R

REC

OR

DIN

G1990


HEAD (AMR)



V

Angle between and

No

rma

lize

Re

sist

an

ce

ρmax

ρmin

Recording Medium

ARM Head

TrackwidthBit

length (B)Recordedtransition





HEAD (GMR)

PER

PEN

DIC

ULA

R

REC

OR

DIN

G

GMR EffectDiscovered in 1988 by Fert and


HEAD (AMR)


NM(Cu)

FM(Fe)


Discovered in 1988 by Fert andGrünberg (Nobel 2007)

H

Hs = field necessary to overcome

the antiferromagnetic coupling

NM(Cu)

FM(Fe)

High resistive state

NM(Cu)

FM(Fe)

FM(Fe)

Low resistive state





HEAD (GMR)

PER

PEN

DIC

ULA

R

REC

OR

DIN

G

GMR EffectDiscovered in 1988 by Fert and


HEAD (AMR)


Mechanism Spin dependent scattering.


Discovered in 1988 by Fert andGrünberg (Nobel 2007)

Low resistive state High resistive state

Two currents model (Mott’s model)There are two conduction channels(“spin-up” and “spin-down”) that areindependent and have differentresistance.F. Mott, Proc. R. Soc. Lond. 153 699 1936

V





HEAD (GMR)

PER

PEN

DIC

ULA

R

REC

OR

DIN

G1990


HEAD (AMR)


SPIN VALVE STRUCTUREFree layer Metal FM


V

Free layerPinned layer

Metal Spacer

Recording Medium

Trackwidth

Bit length (B)Recorded

transition

SPIN VALVE STRUCTURE

B.Dieny et al., PRB 43 1297 1991

Metal Spacer

AFM

FMPinned layer

V





HEAD (GMR)

PER

PEN

DIC

ULA

R

REC

OR

DIN

G1990


HEAD (AMR)


SPIN VALVE STRUCTUREFree layer Metal FM


V

Material performance and device fabrication

were continuously improved as higher

recording densities were achieved.

Free layerPinned layer

Metal Spacer

Recording Medium

Trackwidth

Bit length (B)Recorded

transition

SPIN VALVE STRUCTURE

B.Dieny et al., PRB 43 1297 1991

Metal Spacer

AFM

FMPinned layer

Recording MediumLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

Substrate

Magnetic Medium SEMI-HARD FERROMAGNET

→ It can be permanentlymagnetized permitting information tobe retained over time.

H

M

Mr

Hc

Ms



Substrate

Seed Layer

Underlayer(s)

Intermediate Layer

Magnetic Layer

OvercoatLubricant

Prepared

by

Sputtering

Prepared by

Dip-coatingDiamond Like Carbon – DLC – (~1 nm)Provides chemical and mechanical protection

PFPE (~1 nm)Reduces friction and wear during the head-disk contact

NiAl, CoTi (1 - 10 nm)Promotes the underlayer texture and morphology

Cr-based – Cr, CrV, CrTi, CrMo – (10 - 100 nm)Controls morphology and texture of the magnetic layer

Al-Alloy, GlassPerforms the role of support (hard, stiff, inert, smooth)

CoCr (1 - 50 nm)Enhances the epitaxy growth of the magentic layer


Performs the role of support (hard, stiff, inert, smooth)

MAGNETIC LAYER

CoCr(Pt,Ta,B) Alloy (10 nm)− Pt → Increases Ku → Hsw ≈ Ku/Ms = 4 – 5 kOe

− Cr → Improves grains isolation;

Reduces Ku

− Ta,B additives → Enhances Cr atoms segregation

Granular (<size> = 8 nm) and polycrystalline

Smooth surface (roughness < 5 nm rms)

Stoner-Wolfarth like system

– Single domain grains

– Weakly exchange coupled grains

– Uniaxial in-plane anisotropy Ku

c-axis ≡ easy axis

Co-alloy (HCP)

5 nmc-axis

Core: Co-rich

(magnetic)

Boundary: Cr-rich

(non-magnetic)

Recording ‘Trilemma’Longitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

Conflicting

SNR

0.1

1

10

100

1000

10000

100000 10 Tb/in2


2001 AFC Media

1997 GMR Read Head

1990 MR Read Head

1 Tb/in2

100 Gb/in2

1 Gb/in2

Are

al D

ensi

ty

[Gb/

in2 ]

BPM, High Ku


etc.

?

▲▲▲▲2011 DEMO




ConflictingRequirements

THERMAL

STABILITY

WRITE-ABILITY1960 1970 1980 1990 2000 2010 2020 2030

1E-6

1E-5

1E-4

1E-3

0.01

0.11980 Thin Film WR Head

1 Mb/in2

Are

al D

ensi

ty

Year




Signal to Noise Ratio (SNR)Longitudinal Recording Perpendicular Recording Future Perspectives

Reliable detection of stored data → SNR < 25 dB

The in plane size of the grains (D) was continuously reduced as higher recording densities were achieved


5 nmc-axis


DD

Signal to Noise Ratio (SNR)Longitudinal Recording Perpendicular Recording Future Perspectives

Reliable detection of stored data → SNR < 25 dB

The in plane size of the grains (D) was continuously reduced as higher recording densities were achieved


SNR can be improved by reducing the randomness in the nature of grains

5 nmc-axis


SNR can be improved by reducing the randomness in the nature of grains → reduction of the dispersion in easy axis orientation

Mechanical texturing

process of the substrate

allows to partially orient

the easy axis along the

track direction.

Cr-based underlayer promotes

the parallel orientation of the

c-axis (easy axis) of the HCP

unit cell.

Track direction

Direction of film

thickness

Longitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

Signal to Noise Ratio (SNR)

Dδ

llll

Real

transition

Intended

transition

Bit length (B)

Width of read head

transition parameter

TRANSITION LENGTH


Q = constant related to the head geometryd = head-medium separation

Magnetic layer parametersMr = remanent momentδ = thicknessD = in-plane grain sizeσ = grain size distribution

Mrδ = magnetic thickness



Dδ

llll

Real

transition

Intended

transition

Bit length (B)

TRANSITION LENGTH

Width of read head






Dδ

Bit length (B)

Dδ

llllBit length (B)

Wider transition



Dδ

llll

Real

transition

Intended

transition

Bit length (B)

TRANSITION LENGTH

Width of read head






Dδ

Bit length (B)

Dδ

llllBit length (B)

Wider transition

Grain volume

Thermal StabilityLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

FIELD ACTIVATED SWITCHING THERMAL ACTIVATED SWITCHING

Longitudinal media can beapproximated to a 2D isotropic Stoner-Wohlfarth system.


H2

H1

H2 > H1

Mean time of reversal

Write-abilityLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

Using materials with higher Ku is limited by the writing field (Hx)

Recording Medium

Material ku (107 erg/cm3)

CoCrPtX0.1 – 0.6

↑ku → ↑Pt,↓Cr

Co/Pt(Pd) ~1

Co3Pt 0.6

L10 CoPt 5

L10 FePt 7

The reduction of V can be

counterbalanced by using

material with higher Ku


Write Head

Materialµµµµmax

(103)4ππππMs

(G)Hc

(Oe)

Fe 5 2.15 0.9

Fe49Co49V2 20 2.40 0.5

Ni50Fe50 40 1.60 0.1

Ni80Fe15Mo5 300 0.65 0.01

Recording Medium

δ

d = 20 nm in 2006

Hx

Antiferromagnetically-coupled (AFC) Media


Top FM Layer

Bottom FM Layer

Ru Layer (< 1 nm)Ru thickness is tuned to coupleantiferromagnetically the FMlayers via RKKY interactions.

2001 – The introduction of AFC media allow increasing the recording density up

to 160 Gb/in2


Bottom FM Layer

Smaller transition length

Improved thermal stability

Improved SNR

can be increased Larger grain volume

10

100

1000

10000

100000 10 Tb/in2


2001 AFC Media

1997 GMR Read Head

1 Tb/in2

100 Gb/in2

1 Gb/in2[Gb/

in2 ]

Hard Disk Drive Roadmap


BPM, High Ku


etc.

?

▲▲▲▲2011 DEMO [Co/Pd]n BPM – 1T/in2


?


1960 1970 1980 1990 2000 2010 2020 20301E-6

1E-5

1E-4

1E-3

0.01

0.1

11997 GMR Read Head

1990 MR Read Head


1 Gb/in2

1 Mb/in2

Are

al D

ensi

ty

[

Year

1956 RAMAC



1975Perpendicular

recording was

introduced

General AspectsLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES



Write/Read Head

Free layer

AFM

FM

FMPinned layer

Insulating spacer (e.g.

MgO)

READ HEAD – TUNNELING MAGNETORESISTANCE (TMR)

Mechanism Spin dependent tunneling.


Single pole Head+SUL Guides the magnetic flux

(Φ) from the collector tothe write pole.

“The recording media is

placed in the gap of the

write head”

It is assumed that

the SUL generate

a mirror image of

the main pole

≡

WRITE HEAD


Prepared by

Sputtering

Prepared by

Dip-coatingDiamond Like Carbon – DLC – (~1 nm)Provides chemical and mechanical protection

PFPE (~1 nm)Reduces friction and wear during the head-disk contact

Al, Ti (10 nm)Improve the adhesion of SUL

CoTaZn amorphous (10 - 100 nm)Helps in conducting the flux form the writing pole of the head and

the connector pole

Al-Alloy, GlassPerforms the role of support (hard, stiff, inert, smooth

Ru (20 nm)• Exchange-decouples the SUL and the magnetic layer

• Favours the epitaxial growth of the magnetic layer

Substrate

Adhesion layer

Soft Underlayer (SUL)

Intermediate Layer

OvercoatLubricant

Recording layer


CoCrPt@SiO2

easy-axis

Core: Co-rich

(magnetic)

Boundary: SiO2

(non-magnetic)

CoCrPt@SiO2 (15nm)SiO2 : enhances grain isolation

(allows reducing Cr content→ ↑Ku)

Granular (<size> = 6 nm)

Smooth surface (roughness < 5 nm rms)

Stoner-Wolfarth like system

– Single domain grains

– Weakly exchange coupled grains

– Uniaxial perpendicular anisotropy Ku

MAGNETIC LAYER

AdvantagesLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

MEDIA ALIGNMENT Perpendicular Media

CoCrPt@SiO2

Random easy-axis orientation

Uniform easy axis orientation

Improved SNR

Longitudinal Media

RECORDING FIELD

Writing is performed bythe fringing fields.

The recording media is placed in the

gap of the write head

Hwrite PRM ≈ 2 Hwrite LRM

→


the fringing fields.

STRAY FIELD AT BIT BOUNDARY

δ

write write

→ Improved write-abiilityMaterial with higher Ku can be used

→ Improved Thermal Stability

Ultra narrow transition

→ Improved SNRHigher Mrδ can be used

→ Improved thermal stability

δ

AdvantagesLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

MEDIA ALIGNMENT Perpendicular Media

CoCrPt@SiO2

Random easy-axis orientation

Uniform easy axis orientation

Improved SNR

Longitudinal Media

RECORDING FIELD

Writing is performed bythe fringing fields.

The recording media is placed in the

gap of the write head

Hwrite PRM ≈ 2 Hwrite LRM

→


the fringing fields.

STRAY FIELD AT BIT BOUNDARY

δ

write write

→ Improved write-abiilityMaterial with higher Ku can be used

→ Improved Thermal Stability

δ

Destabilizing stray fields deep inside the bit→ A smaller amount of intergranular interaction is

desired to reduce the destabilizing effects


1E-4

1E-3

0.01

0.1

1

10

100

1000

10000

100000 10 Tb/in2

2011 DEMO [Co/Pd]n BPM - 1 Tb/in2



2001 AFC Media

1997 GMR Read Head

1990 MR Read Head


1 Tb/in2

100 Gb/in2

1 Gb/in2

1 Mb/in2

Are

al D

ensi

ty [G

b/in

2 ]

?



Alternative Materials and Novel Concepts

Areal density > 600 Gbit/in2 (↓Dgrain →

↓Vgrain), CoCrPt@SiO2 media could facea thermal instability problem.


1960 1970 1980 1990 2000 2010 2020 20301E-6

1E-5

Year


Recording Recording

Materialku

(107 erg/cm3)

Co/Pt(Pd) ~1

L10 CoPt 5

L10 FePt 7

Novel concepts to

combine

thermal stability and write-ability issues

• Heat assisted magnetic recording Tilted media

• Exchange-spring media

• Patterned Media• …

Bit patterned media

One dot - One bit

KuV is not longer governed by

Vgrain but rather by the Vdot

SOLUTIONS

Heat Assisted Magnetic Recording - HAMRLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

WRITING PROCESS

A tightly focused laser beam is used to increase themedium temperature up to a value where theanisotropy of the medium is low and thus only a verysmall field is required to switch the media.

Higher Ku materials can be used→ Higher thermal stability

READ-OUT PROCESS

Is performed with a magnetoresistive head at roomtemperature


• Near field optics are required to make the heatspot small enough to avoid thermal erasure ofthe adjacent tracks.

• Recording medium and head need to haveadequate thermal properties.

• New materials for lubricant layer are necessaryto avoid thermal deterioration.

temperature

MAIN CHALLENGES

M. Kryder, Proc. IEEE 96 1810 2008

0.6

0.7

0.8

0.9

1.0

Nor

mal

ized

Sw

itchi

ng F

ield

H

sw /

HK

Tilted MediaLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

Conventional

perpendicular writing

Tilted perpendicular

writing

STONER-WOHLFARTH SYSTEM

[ ] 2/33/23/2 )(sin)(cos−+= ααksw HH


0 15 30 45 60 75 90

0.5

0.6

Nor

mal

ized

Sw

itchi

ng F

ield

αααα (°)

J. Wang, Nature Mat. 4 192 2005

Higher Ku materials can be used

→ Higher thermal stability

z

EA

αααα

yx

Recording medium plane

ΗΗΗΗ )0(5.0)45( °==°= ααswH

Exchange Spring Media - ESMLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

Hsw of an extremely hard magnetic layer can be reduced by a strongly exchange-coupledsofter magnetic film, without affecting thermal stability.

Hn > HpHn < Hp

Hard

Soft

Soft

Hard

Hsw= max(Hp,Hn)


D. Suess et al., JMMM. 321 545 2009

Reversible reversal

A. H = Hn; a wall nucleates in the soft layer.

B.C. The wall propagates to the soft hardinterface where it becomes pinned.

With increasing H the domain wall

becomes compressed.D.E. H = Hp; the bilayer completely reverses.

( )( )

−

+

−≈

hardhard

softsoft

softshards

softhardp AK

AK

MM

KKH 1

22

,0,0 µµ

A = exchange stiffnessThe expression is valid if both layers arethick enough to fit a full domain wall

Exchange Spring Media - ESMLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

Hsw of an extremely hard magnetic layer can be reduced by a strongly exchange-coupledsofter magnetic film, without affecting thermal stability.

Hn > HpHn < Hp

Hard

Soft

Soft

Hard

Hsw= max(Hp,Hn)


Reversible reversal

A. H = Hn; a wall nucleates in the soft layer.

B.C. The wall propagates to the soft hardinterface where it becomes pinned.

With increasing H the domain wall

becomes compressed.D.E. H = Hp; the bilayer completely reverses.

( )( )

−

+

−≈

hardhard

softsoft

softshards

softhardp AK

AK

MM

KKH 1

22

,0,0 µµ

A = exchange stiffnessThe expression is valid if both layers arethick enough to fit a full domain wall

≈

G

hard

ssw t

AK

MH

0

2

µHard

Graded tGKu

GRADED MEDIA

Allow further reduction of Hsw

D. Suess et al., JMMM. 321 545 2009

Bit Patterned Media - BPMLongitudinal Recording Perpendicular Recording Future PerspectivesFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

One e-beam

MAIN CHALLENGE

Extreme fabrication requirements

(low cost, high resolution, large area order)

Potential way:E-beam lithography + nano-imprinting

Density (Tb/in2) Bit period (nm) BAR=1

1 25.4

5 11

10 8


CONVENTIONAL MEDIA• Continuous granular

recording media• Multiple grains per bit

• Boundaries between bits

determined by grains• Thermal stability unit is one

grain

BIT PATTERNED MEDIA• Highly exchange coupled

granular media• Multiple grains per island, but

each island is a single domain

particle• Bit locations determined by

lithography

• Thermal stability unit is one dot

→ larger thermal stability

One e-beam master

template

10000 nanoimprint

stampers

100000 imprinted

disks

Final RemarksFINAL REMARKSHISTORY OF MAGNETIC RECORDING HARD DISK DRIVES

Current HDDs • Perpendicular Mode• Recording Density: 600 Gb/in2


• Recording Density: 600 Gb/in• HDD sold in 2010: 700 million• Cost/Gbyte: 0.10 $

Emerging technologies for magnetic information storage

Race Track Memory Magnetic Random Access Memory (MRAM)

Recommended readings

REVIEWS

− Piramanayagam S N et al., Recording media research for future hard disk drives, Journal ofMagnetism and Magnetic Materials 321 485 2009

BOOKS

− Plumer M L, van Eck J and Weller D (editors), The physics of ultra-high density magneticrecording, Springer 1999

− Piramanayagam S N and Chong T C (editors), Developments in data storage, John Wiley &Sons 2011

− Khizroev S and Litvinov D (editors), Perpendicular magnetic recording, Kluwer Academic 2009


Magnetism and Magnetic Materials 321 485 2009− Parkin S S P et al., Magnetic domain-wall racetrack memory, Science 320 190 2008− Piramanayagam S N, Perpendicular recording media for hard disk drives, Journal of Applied

Physics 102 011301 2007− Richter H J, The transition from longitudinal to perpendicular recording, Journal of Physics D:

Applied Physics 40 R149 2007− Richter H J et al., Media for magnetic 100 Gbit/in2, MRS Bulletin 31 384 2006− McFadyen et al., State-of-the-Art magnetic hard disk drives, MRS Bulletin 31 379 2006− Comstock R L, Modern magnetic materials in data storage, Journal of Materials Science:

Materials in Electronics 13 509 2002− Moser A et al., Magnetic recording: advancing into the future, Journal of Physics D: Applied

Physics 35 R157 2002− Richter H J, Recent advances in the recording physics of thin-film media Journal of Physics D:

Applied Physics 32 R147 1999

[email protected] ITALIAN SCHOOL OF MAGNETISM | Pavia | February 5-10, 2012

magnetic recording - italian school of magnetism 2012

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