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

CO 80305-5602 August 21-22, 2007

A-ME technology for linear application

Seiichi OnoderaMetal Evaporated Product Development Dept. Tape Media Div.

Chemical Device Business Group, Sony Corporation3-4-1 Sakuragi,Tagajo-shi,Miyagi-ken.985-0842 Japan

Phone:+81-22-367-2460 FAX: +81-22-367-2589E-mail: Seiichi.Onodera@jp.sony.com

Outline

Background of tape storage media

Advanced ME tape media Potential-Process of A-ME tape media-Microstructure of A-ME media-Properties and feature of A-ME media

A-ME media for Linear System-Single Layer-Herringbone Structure-Perpendicular

Summary

A-ME Tape Media PotentialTo demonstrate the capability of Co-CoO ME media for higher areal recording density more than 20Gbit/in2

Advantages of ME tape– Industry elaborated technology : DVC, MMV, AIT– Using GMR head, potential of the recording density of

11.5Gbit/in2 was already demonstrated in 2002 [1][1] T. Ozue et al., “11.5-Gb/in2 recording using spin-valve heads in tape systems,” IEEE Trans. Magn., vol. 38, pp. 136-140, 2002.

Recording density of tape system is essential more, according to drastic improvement of HDD drives!

0.01

0.1

1

10

100

1000

1990 1995 2000 2005 2010 2015Year

Are

al d

ensi

ty (G

b/in

ch2 )

HDD in R&D

HDD products

Helical system in R&DHelical system products

Helical INSIC Roadmap

Linear system in R&D

Linear system LTOLinear INSIC Roadmap

DVC

AIT-1

AIT-5AIT-4MMV

AIT-3AIT-2

LTO-1

6.67Gb/in2

(IBM/Fujifilm)

11.5Gb/in2

(Sony)

LTO-4LTO-3

LTO-2

23Gb/in2

Advanced Metal Evaporated Tape Structure

Base Film

Back　Coating

LubricantLayer

EvaporatedLayer

DLCProtective

Layer

Magnetic Layer Structureof Metal Evaporated Media with DLC Layer

Tape structure of A-ME

Evaporation Process on A-ME tape• Evaporated by web-coating in vacuum• Pure cobalt is evaporated from crucible.• Oxygen is introduced during deposition.• Tilt angle of columnar structure is defined by mask.

An example of a cross sectional TEM image of Co-CoO recording layer (Top). Processed image by inverse FFT using Co and CoO reflections (Bottom). Detail techniques are described in reference by T. Ito et al [2].

[2] T. Ito, Y. Iwasaki, H. Tachikawa, Y. Murakami and D. Shindo,“Microstructure of a Co–CoO obliquely evaporated magnetic tape,” J. Appl. Phys., vol. 91, pp. 4468-4473, 2002.

Co Crystallites

CoO Crystallites

Microstructure of A-ME tape

Cross-sectional HREM image (JEOL JEM-3000F at 300kV) Processed image

１０ｎｍ

Ｃｏ

ＣｏＯＣｏＯ １１１

Ｃｏ １０１ ００２

Filtering spots

FFT

Inverse FFT

HREM image

T.Ito, Y.Iwasaki, H.Tachikawa, Y.Murakami, Z.Liu and D.Shindo,J.Appl.Phys.91(2002)4468

Sample SpecificationsImproved points comparing with previous reports are;

Smoother base filmNarrowed incident angle region– The final incident angle was narrowed from 45˚ to 50˚.

Thicker Co-CoO recording layer– Optimized Mrt for tested GMR head, and an oxidation

condition for maximize CNR of the media. Mrt of media was designed to be 10mA with 35nm-thick recording layer.

Base FilmBase Film

Protective Carbon (8nm) and Lubricant coatingProtective Carbon (8nm) and Lubricant coating

CoCo--CoO Recording Layer (35nm)CoO Recording Layer (35nm)

Properties of Experimental Samples

ME tape-A (11.5Gb/in2 demo) Ra = 2.7nm

ME tape-B (Newly developed) Ra = 1.8nm

AFM images

ME tape-A ME tape-B

11.5Gb/in2 demo

Newly developed

Thickness of Co-CoO layer (nm) 28 35

Saturation Magnetization Ms (kA/m) a 276 398

Coercivity (kA/m)a 125 133

Mrt (mA) a 4.8 9.9

Squareness a 0.62 0.71

Uniaxial Anisotropy Constant Ku (J/m3) 1.6×105 2.5×105

Magnetic Activation Volume Vac (m3) a 3.0×10-24 2.7×10-24

Thermal Stability KuV/kBT 116 160

Roughness Average Ra (nm) 2.7 1.8

Maximum Roughness Depth Rz (nm) 35.0 27.8

Pulse Width at Half-maximum PW50 (nm) 139 129 a Measured along the longitudinal direction

Angular Dispersion of Magnetic Properties

• ME tape-B has higher squareness around magnetic easy axis, implying better orientation.

• The easy axis is tilted to in-plane direction due to the evaporation angle.

Hexθ

VSM measurement

(a) (b)0 20 40 60 80 100 120 140 160 180

0

20

40

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100

120

140

160

180

200

External Field Angle to Samples Plane (degree)

Coe

rciv

ity H

c(kA/

m)

ME tape-A ME tape-B

0 20 40 60 80 100 120 140 160 1800.0

0.2

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1.0

Squ

aren

ess

(a) (b)0 20 40 60 80 100 120 140 160 180

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200

External Field Angle to Samples Plane (degree)

Coe

rciv

ity H

c(kA/

m)

ME tape-A ME tape-B

0 20 40 60 80 100 120 140 160 1800.0

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1.0

Squ

aren

ess

0 100 200 300 400 5000.0

0.5

1.0

1.5

2.0

2.5

Saturation Magnetization Ms(kA/m)

Ani

sotro

py C

onst

ant K

u (10

5 J/m

3 )

0

20

40

60

80

100

120

140

160

Coe

rciv

ity H

c (kA

/m)

Tunable Uniaxial Anisotropy of Co-CoO Layer

• The improvement on Ku from 1.6×105 to 2.5×105J/m3 is due to increase of Ms.

• The contents of cobalt increase with decreasing oxygen contents.

• In this region of Ms, uniaxial anisotropy of a cobalt grain itself does not change so much, and Kuvaries simply with total contents of cobalt particles in the recording layer [3]. Co

CoOThis figure is combined plot from the results of Fig. 1(a) and Fig. 3(a) in reference 3.[3] K. Motohashi and S. Onodera, “Thickness and oxidation dependence of magnetic properties of ultrathin obliquely evaporated Co-CoO media,” IEEE Trans. Magn., vol. 39, pp. 2350-2352, 2003.

Read/Write characteristics• Measurement Equipment : Drum tester• Relative R/W velocity : 3.5m/sec.

• Despite thicker Co-CoO recording layer, PW50 of ME tape-B was sharpened from 0.139µm to 0.129µm.

0 100 200 300 400 500 600

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0.30

Time (nsec.)

Out

put V

olta

ge (V

)

ME tape-A ME tape-B

Specifications of R/W headsWrite head structure Thin-film inductive

Write width (µm) 2.0

Write gap length (µm) 0.16

Read head structure Shielded spin-valve

Effective read width (µm) 0.5

Read shield-to-shield gap length (µm) 0.1

Signal and Noise spectrum• Lager Mrt made higher signal output and noise level of ME tape-B.

However, the noise level was saved relatively smaller, gained 1.8dB CNR totally.

0 10 20 30 40-80

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0

Frequency (MHz)

Out

put (

dBm

)

ME tape-A ME tape-B System Noise

A wavelength at 20MHz is 0.175µm.

SNR calculation

•Partial response class IV (PR4) Equalization•SNR was obtained from eye patterns•21.5dB was obtained for ME tape-B at 374kFCI

–3.5dB margin to 18dBTw: Narrowed from 0.5µm to 0.23µm

–8/10 coding299kBPI (374kFCI)

–Read/Write width ratio : 0.70.23µm / 0.7 = 0.33µm (77kTPI)

250 300 350 400 450 50015

16

17

18

19

20

21

22

Linear Density (kFCI)

SN

R (d

B)

ME tape-A ME tape-B

299 299 kBPIkBPI ××77 77 kTPIkTPI = = 23.0 Gbit/in23.0 Gbit/in22

Supplement Results• The latest measurement with 0.14µm-track width read head

verified a capability of 23.0Gb/in2, directly. • A square-root rule on SNR will holds until Tw of 0.14µm with

Co-CoO ME tape and GMR heads.

250 300 350 400 450 50014

15

16

17

18

19

20

21

22

Linear Density (kFCI)

SNR

(dB)

ME tape-A with 0.5µm-width GMR ME tape-B with 0.5µm-width GMR ME tape-B with 0.14µm-width GMR

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.714

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23

Read Track Width (µm)

SNR

(dB)

ME tape-B with 0.5µm-width GMR ME tape-B with 0.14µm-width GMR Calculated curve

Write head structure Thin-film inductive

Write width (µm) 0.40

Write gap length (µm) 0.11

Read head structure Shielded spin-valve

Effective read width (µm) 0.14

Read shield-to-shield gap length (µm) 0.066

Dibit response

•Echo of the dibit response indicate nonlinear distortion is still small at 374kFCI.

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Bit Cell (bit)

Ampl

itude

Measured on ME tape-B

Roughness effect on SNR

• To evaluate ONLY roughness effect on SNR, two base films were prepared and evaporated under the same condition.

• Factors in 2.1dB difference are– Irregular magnetization reversal (See MFM images)– Increased head-to-media spacing– Fluctuation of head-to-media spacing

ME tape-C ME tape-D

Rougness average Ra (nm) 3.0 2.0

SNR at 374kFCI (dB) 19.4 21.5

MFM imagesRa=3.0nm Ra=2.0nm

Helical Scan Recordinｇ SystemLinear Recording System

BOT EOT BOT EOT

A-ME media for Linear System

Single Layer

Herringbone

Perpendicular

EQ1EQ2

A-ME candidate for linear system

Head Write : MIG Read : AMRTrack width 12 µm 9 µmGap length 0.21 µm 0.23 µm

Tape ME tapeThickness Magnetic Layer : Co-O 45 nm

Protective Layer : DLC 8 nmMr・t 17.2 mA (1.72 memu/cm2 )Coercivity : Hc 105 kA/m (1320 Oe)

Rotating Drum Tester Head/Tape relative speed: 6.8 m/s

The basic properties of write head, read head and tape

Single layer for linear systemEQ1EQ2

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0 10 20 30 40 50 60

Iw (mApp)

Reverse directionMin. PW50: 0.32μmIwr: 25mApp

Forward directionMin.PW50: 0.25μmIwf: 30mApp

Wavelength : 6.8μm

(a)

0.26

0.28

0.30

0.32

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0.36

0 10 20 30 40 50 60

Iw (mApp)

Reverse directionIS-TAA: 0.341Vppat Iwr

Forward directionIS-TAA: 0.317Vppat Iwf

(b)

Wavelength : 6.8μm

The write current (Iw) dependence of PW50 (a) and IS-TAA(b)for isolated pulses in forward and reverse direction

100 200 300 400 500

-0.2

-0.1

0.1

0.2

(a)

Amplitude (V)

Time (x 2ns)

Forward directionIw: 30mAppIS-TAA: 0.318VppPW50: 0.25μm

100 200 300 400 500

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-0.1

0.1

0.2

(b)

Amplitude (V)

Time (x 2ns)

Reverse directionIw: 25mAppIS-TAA: 0.341VppPW50: 0.32μm

The shape of isolated pulses in forward (a) and reverse (b) direction

(a) Forward direction

Rec. Dens. :207kfci

SDNR:22.1dB

(b) Reverse direction

Rec. Dens. :170kfci

SDNR:22.9dB

Eye patterns in forward (a) and reverse (b) direction

after PR4 equalization

The digital-recording performance of obliquely oriented Metal Evaporated tape in the reverse direction

Forward direction Reverse directionLinear recording density (kfci) 170 207 311 170 207Nyquist frequency (MHz) 22.7 27.8 41.7 22.7 27.8Wave length λ (µm) 0.30 0.25 0.16 0.30 0.25Channel NLD 1.67 2.04 3.18 2.14 2.61PW50 (µm) 0.25 0.25 0.26 0.32 0.32SNRhn (dB) 26.5 23.4 25.6 21.9SNRin (dB) 27.5 24.1 26.8 24.7Write current : Iw (mApp) 38 36 35 28 28SDNR after PR4 equalization (dB) 25.6 22.1 18.4 22.9 20.2

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25

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150 200 250 300 350

Linear recording density (kfci)

Low cut filter:50kHz

Forward direction

Reverse direction

-13％

-14％

t=55nm

The digital-recording performance of obliquely oriented Metal Evaporated tapein the reverse direction

Takashi Kawashima, Youichi Kanemaki, Takanori Sato,Wataru Okawa, and Yutaka Okazakia).

Herringbone structure for linear system

ME-1 ME-2

Coercivity (KA/m) 120 110

Mrt total (mA) 57 32

Squareness 0.8 0.8

Magnetic Layer Thickness (nm) 160 30+60

Back Coat Thickness (um) 0.5 0.5

Substrate(PET) Thickness (um) 6.5 6.5

Total Thickness (um) 7.0 7.0

Samples

Herring Bone

Frequency dependence of signal amplitude

-50-45-40-35-30-25-20-15-10

0 5 10 15 20Frequency [MHz]

signa

l am

plitu

de [d

Bm

ME001

ME001 (reverse)

ME002

ME002 (reverse)

Frequency Response

PR(1,1) equalized spectrum of 2T single tone carrier

-100

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0

20

0 5 10 15 20Frequency [MHz]

ampl

itude

[dB

]

ME001 carrier spectrumME001-rev. carrier spectrumME001 signal amplitudeME001-rev. signal amplitudePR (1,1) equalizer

tape speed v = 6.66m/srecording density λmin = 0.33um (20MHzWrite head HMR ? Tw = 13um gap = 0.18umRead head amorphous Tw = 8um gap = 0.15umSpectrum analyzer RBW 30kHz VBW 1kHz sweep time 3.2sec

ME001 : 21.5dBME001-r : 18.3dB

ME1 Analog PR1 Forward/Reverse SNR @152kfci

PR(1,1) equalized spectrum of 2T single tone carrier

-100

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-60

-40

-20

0

20

0 5 10 15 20Frequency [MHz]

ampl

itude

[dB

]

ME002 carrier spectrumME002-rev. carrier spectrumME002 signal amplitudeME002-rev. signal amplitudePR (1,1) equalizer

tape speed v = 6.66m/srecording density λmin = 0.33um (20MHzWrite head HMR ? Tw = 13um gap = 0.18umRead head amorphous Tw = 8um gap = 0.15umSpectrum analyzer RBW 30kHz VBW 1kHz sweep time 3.2sec

ME002 : 20.5dBME002-r : 20.8dB

ME2 Analog PR1 Forward/Reverse SNR @152kfci

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0

0.05

0.1

0.15

0.2

1600 1800 2000 2200 2400

Time Point

ME001 (Forward Direction)

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0

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0.1

0.15

0.2

1600 1800 2000 2200 2400

Time Point

ME001 (Reverse Direction)

Regular Double Layer For Helical Scan80nm

80nm

Conventional Double Layer A-ME Characteristics

Forward Direction Reverse Direction

Herringbone Double Layer For Linear 30nm

60nm

Herringbone Layer A-ME Characteristics

Forward Direction Reverse Direction

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0

0.05

0.1

0.15

0.2

1600 1800 2000 2200 2400

Time Point

ME002 (Forward Direction)

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0

0.05

0.1

0.15

0.2

1600 1800 2000 2200 2400

Time Point

ME002 (Reverse Direction)

0 deg（Longitudinal）

90 deg（Perpendicular）

Oxygen atmosphere

Cooling can

Mask

Base film

Crucible(magnetic material)

Process

Perpendicular for linear system

Perpendicular

0

20

40

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120

0 30 60 90 120 150 180

Fieid Angle Relative to Tape Plane [deg]

0

1

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3

4

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6

Hysteresis Loop

Magnetic properties

Angular dependence of Hc⊥ and Mr・t⊥

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-5

0

5

10

15

-1000 -500 0 500 1000External Field Hex [kA/m]

M・

t [m

A]

0deg90deg

Hc⊥[kA/m]

Mr・t ⊥[mA]

Hc⊥Mr・t⊥

Isolated Pulse(New P-ME)

-0.1

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-0.06

-0.04

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0

0.02

0.04

0.06

0.08

0.1

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Time（nsec）

Output（V）

New P-ME Forward

New P-ME Reverse

Isolated Pulse

Areal Density [ Gbits/inch2]

CY1988 1990 1992 1994 1996 1998 2000 2002

1

0.1

10

100

2004

DVC AIT-3

AIT-4

AIT-2Linear tape

2006 2008

1,000

R&D

AIT-1

MMV

2010 2012 2014 2016

Magnetic tape

HDD R&D

Tape R&D

2007

Hard Disk

R&D

SAIT-１

Helical Scan

S-DLT, LTO

SRCRead Rite

11.5Gb/in2

4.5Gb/in2

Fujitsu

Recording Density Trend

IBM

Seagate

Toshiba

HGSTSeagate

Year of Commercialization

IBM

LTO-1LTO-2

LTO-3

10,000

AIT-5

LTO-4

ATP

INSIC

INSIC

INSIC

Summary• To demonstrate the highest areal recording density of tape

media, we have developed a metal evaporated (ME) tape with higher magnetic anisotropy of 2.5×105J/m3 and finer magnetic activation volume of 2.7×10-24m3 of a Co-CoO recording layer deposited on a smoother base film.

• A capability of an areal recording density of 23.0Gbit/in2 was confirmed using a GMR head as a read head.

• By using a single layer structure with two equalizer or herringbone structure, ME tapes can be used with linear recording system.

• Perpendicular structure shows the equivalent bidirectional recording properties and possible application for linear system.