THIC – 8/22/071

Presented at the THIC Meeting at the National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder CO

80305-5602 August 21-22, 2007

Transition from AMR to GMR Headsin Tape Recording

John P. NibargerSun Microsystems

1450 Infinite Dr., Louisville CO 80027-9440Phone: +1-303-661-2837 FAX: +1-303-661-8992

E-mail: john.nibarger@sun.com

THIC – 8/22/072

• Basics of magnetic recording> AMR (Anisotropic Magneto-Resistance)> GMR (Giant Magneto-Resistance)

• Transition in disk from AMR to GMR• Issues surrounding the transition from

AMR to GMR in tape

Outline

THIC – 8/22/073

*

*Using a peak detect channel

Head writes datato media

Media stores data

Head reads data from media

Channel convertsanalog signal to digital user data

Channel convertsdigital user data to

analog signal

Digital Magnetic Recording

THIC – 8/22/074

• Allow system to resolve changes in the magnetic media which stores the user information

• Two types in magnetic recording> Inductive: Faraday’s Law ( )> Magneto-Resistive (MR): electric resistance of the

sensor changes with applied magnetic field

t∂∂−=×∇ BΕ

Rotation of the magnetization in a MR sensor gives rise to a resistivity change (∆ρ)

( )θρρρ f⋅∆+= 0

tdwIRIV ⋅∆⋅=∆⋅=∆ ρ

Magnetic layer

Magnetic sensor

Magnetic flux

Magneticmoment

wd

t

Magnetic Read Sensors

THIC – 8/22/075

• Inductive> A variable magnetic field from the media will induce a variable

voltage in a coil• Anisotropic magneto-resistance (∆ρ/ρ ~ 2% in Ni80Fe20)

> Bulk effect in ferromagnetic materials• Giant magneto-resistance (∆ρ/ρ ~ 20% in Co/Cu/Co)

> Interface effect in thin multilayers• Tunneling giant magneto-resistance (∆ρ/ρ ~ 250% in Co/MgO/Co)

> Coherent tunneling effect across an insulator

GMR

Tape

Disk

Inductive AMR GMR

Inductive AMR TMR

1985 2010 ??

1992 1997 2006IBM Corsair IBM Deskstar 16GP Seagate Momentus II

IBM 3480

Tape and Disk Sensor Technology

THIC – 8/22/076

• Tape area – width (½”) and length (900 m)> ~ 18,000 in2

• Disk area – area of a platter and number of platters> ~ 8 in2 for 1 single-sided platter

Direction of media travel

Tracks per inch (tpi)

bits per inch (bpi)

Areal density (bits/in2) = tpi· bpi

shieldssensor

Magnetic Recording

THIC – 8/22/077

0.01

0.1

1

10

100

1000

1990 1995 2000 2005 2010 2015 2020

Disk ProductTape ProductTape INSIC Roadmap

GMR

Tape

Disk

Inductive AMR GMR

Inductive AMR TMR1985 2010 ??1992 1997 2006

Year of Introduction

Area

l Den

sity

(Gb/

in2 )

INSIC EHDR demo goal

16 TB

2 TB

THIC – 8/22/078

• Anisotropic Magneto-Resistance (AMR) is a bulk effect in Permalloy (Ni80Fe20) and other ferromagnetic materials> Optimum bias at 45 degrees

( ) ( )20 cosAMRH Hρ ρ ρ θ= + ∆

current

magnetization

θ

AMR:

Goal is to offset the bias field

Vary field with tape

Rectified SensorOutput

R

H

Vary field with tape

SensorOutput

R

H

AMR Response

THIC – 8/22/079

Cap

Sensor

Soft Adjacent Layer(SAL)

Spacer

SubstrateSeed

45 – 80 nm

25-45 nm

7-12 nm

15-25 nm

Cap

Ni80Fe20

Co90Zr5Mo5

Ta

SubstrateSeed

AMR Sensor Stack Materials

THIC – 8/22/0710

• AMR is a good sensor (and still used by tape)

• BUT, it has a problem. Output decreases as sensor thickness decreases

• Why has sensor thickness decreased over time?

Tape head AMR layerthickness and year of Sun/STK product introduction

0

5

10

15

20

0 100 200 300 400 500 600

∆R/R

(%)

Sensing Layer Thickness (Angstroms)

AMR

2006 2003 1999 1993

Why Switch from AMR?

THIC – 8/22/0711

Magnetic sensor

Magnetic flux

Magneticmoment

Tape magnetic layer

Tape substrate

Thick media → low density → lots of fluxThick sensor to match flux

Thin media → high density → less flux Thin sensor to match flux

Sensor for higher densities:1. Thinner sensor (for thinner media)2. Higher sensitivity (to make up for

reduced flux)

Achieving Higher Densities

THIC – 8/22/0712

Thinning the sensor allows higher density BUT the signal goes down!

Want something that can increase output with decreasing sensor thickness

0

5

10

15

20

0 100 200 300 400 500 600

∆R/R

(%)

Sensing Layer Thickness (Angstroms)

AMR

2006 2003 1999 1993

Decreasing Thickness Penalty in AMR

THIC – 8/22/0713

AMR is a bulk effect, interfacial scattering takes over at small thicknesses

GMR is an interface effect

0

5

10

15

20

0 100 200 300 400 500 600

∆R/R

(%)

Sensing Layer Thickness (Angstroms)

GMR

AMR

Advantage of GMR

THIC – 8/22/0714

Pinned Layer

Free Layer

Non-magnetic Spacer

Anti-aligned momentsHigh Resistance

Pinned Layer

Free Layer

Non-magnetic Spacer

Aligned momentsLow Resistance

GMR – Spin Dependent Scattering

THIC – 8/22/0715

( ) ( )0 sinGMRH Hρ ρ ρ θ= + ∆

• GMR is an interface effect> Bias at 0 degrees R

esistanceFree

Pinned

pinned

Cu spacer

Applied Field

Vary field with tape

SensorOutput

Vary field with tape

SmallSensorOutput

GMR:

Goal is to zero the bias field

R

H

R

H

free

GMR Response

THIC – 8/22/0716

• GMR structures act as a spin valve> Resistance depends on direction of applied

magnetic field on the sensor

• 3 important components> Free layer

> Well behaved> Properly oriented and biased

> Non-magnetic spacer > Interface properties are important

> A solid pinned layer> Won’t move with field from tape

Cap

Free Layer

Pinned Layer

Non-magnetic spacer

SubstrateSeed

How Do We Make These Structures?

THIC – 8/22/0717

Cap

Co90Fe10

Seed

Cu

Substrate

Pt50Mn50

Co90Fe10

Ru (10 Ǻ)

Ni80Fe20

Co90Fe10

Cap

Free Layer

Pinned Layer

Spacer

SubstrateSeed

Ru atomic radii ~ 2.6 Ǻ 10 Ǻ

5-15 nm

2-3 nm

10-40 nm

magnetization

Ǻ = 10-10 m

GMR Sensor Stack Materials

THIC – 8/22/0718

-2000

0

2000

4000

6000

8000

10000

12000

-10 -5 0 5 10

Ibias (mA)Pe

ak to

pea

k vo

ltage

(uV)

GMR 5 um reader 1.5 um stripeGMR 2.5 um reader 1.3 um stripeGMR 1 um reader 1 um stripeAMR 5 um reader 1.6 um stripe

100

1000

10000

100000

0 2500 5000 7500 10000 12500 15000density (frmm)

Vpp

(uV)

NGD-B

NGD-C 41 (1 um stripe)GMR prototype sensorAMR sensor

5 µm reader width comparison

( )( )

9% 4.52%

GMR

AMR

RR

RR

∆= =

∆

frmm = flux reversals per mm

GMR at Sun

THIC – 8/22/0719

• Providing leading edge head technologies for Enterprise, Mid-Range, and Low-End tape drive products.> Sun Microsystems T10000 and 9x40 product lines; LTO2-LTO4> The first thin film helical scan read & write heads in production with VXA-3

• Developing the technology building blocks for future generation products now> GMR, increased device density, advanced materials

• Custom designed equipment technology to meet the unique requirements of tape head manufacturing> Dynamic testers, head assembly, critical dimension measurement

• State-of-the-art performance analysis capabilities to ensure product quality and competitive position> Dynamic performance, constructional analysis, magnetics analysis

Recording Head Operations at SunLouisville, CO

THIC – 8/22/0720

GMR

Gallagher and Parkin, IBM J. Res. Dev. 50, 5 (2006)

TMR

GMR to TMR

THIC – 8/22/0721www.hitachigst.com/hdd/technolo/gmr/gmr.htm

AMR to GMR Transition for IBM

THIC – 8/22/0722

AMR to GMR Transition for tape

9940B (2002), 0.2 Gb/in2 (200 GB)

T10000 (2006), 0.4 Gb/in2 (500 GB)

INSIC (2007), 0.8 Gb/in2 (1 TB)

INSIC (2011), 2.7 Gb/in2 (4 TB)

INSIC (2009), 1.5 Gb/in2 (2 TB)

INSIC (2013), 5 Gb/in2 (8 TB)

02 04 06 07 09 11 13 15 ~ 12 year technology offset

INSIC (2015), 10 Gb/in2 (16 TB)

20xx

CGR = 40 %INSIC high bpi scenario

THIC – 8/22/0723

0.01

0.1

1

10

100

0.1 1 10 100

reader width (um)

area

l den

sity

(Gb/

in^2

)

10

100

1000

100 1000 10000 100000

tpi

kbpi

• Disk change to GMR ~ 2 - 5 Gb/in2

• Tape change to GMR ~ 1 - 2 Gb/in2

Disk - AMRDisk - GMRTapeTape (high bpi)Tape (high tpi)

2005 INSIC roadmap

Areal Density

THIC – 8/22/0724

Disk - AMRDisk - GMRTapeTape (high bpi)Tape (high tpi)

10

100

1000

0.1 1 10 100

reader width (um)

kbpi

100

1000

10000

100000

0.1 1 10 100

reader width (um)

tpi

Read width = ½ track width

• Disk change to GMR ~ 1 µm, but only at 200 kbpi• Tape change to GMR ~ 2 - 3 µm, but only at 300 - 400 kbpi

2005 INSIC roadmap

Kbpi and Tpi

THIC – 8/22/0725

1

10

100

1000

0.1 1 10 100

reader width (um)

BA

R

1

10

100

1000

0.01 0.1 1 10 100

areal density (Gb/in^2)

BA

R

BAR = bpi/tpi= W/L

L W

Tape has much higher BAR since bpi is pushed more

Disk - AMRDisk - GMRTapeTape (high bpi)Tape (high tpi)

Bit Aspect Ratio (BAR)

THIC – 8/22/0726

• Similarities> Fundamental physics of recording is identical

• Differences> Interchange is needed for tape> Disk is a “closed” environment compared to tape

> Contamination and corrosion> Tape does read while write> Area (18,000 in2 vs. 8 in2)> Rigid disk vs. flexible tape media (sputtered vs. particulate)> Number of tracks

> 32 data + 4 servo tracks in Sun T10000 drive (crosstalk is a major issue)> But disk can have lots of platters (5 two-sided disks with 10 heads)

> Manufacturing yield: tape, 36/36 with 36 tracks, disk, 1/1> (device yield)36 = head yield> (83% device yield)36 = 0.1% head yield> (99.5% device yield)36 = 83% head yield

Similarities and Differences

THIC – 8/22/0727

• GMR sensors are extremely sensitive to ESD

• Two failure modes– High temperatures melt and

fuse materials together– Moderate temperatures heat

PtMn anti-ferromagnet above it’s blocking temperature

• PtMn can reorient ~ 350º C• NiFe free layer ~ 660 º C• Cu spacer ~ 1000 º C

(Al Wallash – Maxtor Corporation)

Electro-Static Discharge

THIC – 8/22/0728

• Hard drive> Preamp on slider

• Tape > Long flex to preamp

(Al Wallash – Maxtor Corporation)

HBM

Fai

lure

Vol

tage

(V)

0

50

100

150

200

250

1990 1995 2000 2005

AMRGMR

Year

2006 Maxtor hard driveSun T10000 head, flex, and voice coil

ESD Sensitivity

THIC – 8/22/0729

• Fundamental physics will drive the transition from AMR to GMR in tape just as it did in disk> Disk migrated at 2 – 5 Gb/in2, ~ 200 kbpi, and 1 µm reader width> Tape will migrate ~ 1 – 2 Gb/in2, ~ 300 – 400 kbpi, and 2 – 3 µm

reader width• Engineering tradeoffs have pushed disk to high tpi and tape

to (relatively) high bpi due to track following issues in tape• Disk migrated to GMR successfully (and then TMR)• Tape will migrate to GMR but issues exist

> Corrosion> ESD> Media

Conclusion

THIC – 8/22/0730

Questions?