High Anisotropic Media for Perpendicular and Heat Assisted

Magnetic Recording 

Lesley Wears, Dave Newman

The magnetic recording industry is aiming to attain areal densities of around 1Tb/in2 before 2010

To attain densities beyond this and retain data integrity has dictated the adoption of very high anisotropy media necessitating in turn some form of “heat assist” for the recording process

The ideal medium for supporting magnetic recording at and beyond areal densities of 1Tb/in2 would be a mono-dispersion of highly anisotropic, non-interacting, single domain particles with TB < TC.

Patterned media produced using lithographic and/or etching processes

Self assembling arrays produced via complex chemical or biological routes

Dots silicon dioxide pillars and cobalt palladium layers

Sputtering onto a seed layer to orientate c axis

Post annealing and orientation of c axis by layering

20022002 Longitudinal mono-disperse particulate media produced by

Rapid Thermal Processing (RTP) of Co-Sputtered pre-curser material

20032003 In response to direction that industry is moving the process

has been modified to produce particulate perpendicular media

Our SolutionOur Solution

A combination of reactive sputtering and Rapid A combination of reactive sputtering and Rapid Thermal Processing TechnologiesThermal Processing Technologies

2. Power to Cobalt and Platinum targets switched off and thin Silicon Nitride protective overlayer deposited.

1. Cobalt Nitride reactively co-sputtered with unreactive Platinum on to glass substrate to produce precursor layer.

3. Precursor medium undergoes Rapid Thermal Processing in 8kWatt vacuum optical oven when

(a) Cobalt nitride disassociates with the release of Nitrogen which escapes by diffusion through overlayer

(b) Released Cobalt alloys with the Platinum

(c) The correct peak processing temperature develops the L10 phase with an orientated tetragonal structure

(c) PtCo condenses on substrate as a near monolayer of monodisperse particles

-6 0 6

-0.2

0

0.2

5000C

70W

Applied Field / kOe

-500

0

500

-6 0 6

5000C

70W

Applied Field / kOe

-0.2

0

0.2

5000C

40W

-500

0

500

5000C

40W

-500

0

500

5000C

30W

-0.2

0

0.2

5000C

30W

-500

0

500

5000C

20W

Ms

-0.2

0

0.2

5000C

20W

k

-0.2

0

0.2

5000C

50W

-500

0

500

5000C

50W

-500

0

500

5000C

60W

-0.2

0

0.2

5000C

60W

-0.2

0

0.2

5000C

40W

-500

0

500

5000C

40W

Optimum sputtering powers to the Co and Pt targets is determined by comparing the in and out of plane hysteresis loops as a function of composition. The following sequence shows the results of maintaining 50W to the Co target whilst varying that to the Pt target between 20W and 70W.

It is found that although Pt sputters much faster than Co the reactive nature of the CoN deposition process determines that the ratio of Co to Pt in the precursor films is optimised at 1:1 when the sputtering powers are near matched.

500

2500

20 40 60

40W

Cou

nts

500

2500

20 40 60 80

CoPtCoPt3

70W

500

2500

20 40 60

30W

2

0

1

2

3

4

30 45 60 75

In PlaneOut of Plane

Pt percentage in processed film

Hc

/ kO

e

Far

aday

Ro

tati

on

/ A

rb.u

nit

sF

arad

ay R

ota

tio

n /

Arb

.un

its

Applied Field / kOeApplied Field / kOe

200oC

-40 -20 0 20 40

300C

-40 -20 0 20 40

500C

450C

-40 -20 0 20 40

650oC

-3000

0

3000

-6 -3 0 3 6

Applied Field / kOe

Ms

-3000

0

3000

-6 -3 0 3 6

Applied Field / kOe

Ms

-3000

0

3000

-6 -3 0 3 6

500o

650o

300o

Applied Field / kOe

Ms

0

2500

5000

20 40 60 80 100

650C

Counts

0

2500

5000

20 40 60 80 100

500C

40 60 80 100

500C

650C

0

0.002

0.004

0.006

0.008

0.010

0 100 200 300 400

Linear Density / kfci

Normalised Noise Power

-2.0

-1.5

-1.0

-0.5

0

0.5

0 100 200 300 400 500

Linear Density /kfci

Normalised TAA

0

1

2

3

15.0 17.5 20.0 22.5

T1/2

/K1/2

Hc

/ kO

e

k

KVTB 25

0

0.015

0.030

0.045

0 100 200 300 400

Linear Density / kfci

Normalised Noise Power

-0.5

0

0.5

0 2 4 6

Field / kOe

M

-1.0

-0.6

-0.2

0 100 200 300 400

Linear Density / kfci

Normalised TAA

Probe Storage

0

300

600

900

1200

1500

0 2 4 6 8 10

100(m)-1

50m)-1

Voltage (V)

Max

imu

m T

emp

erat

ure

(K

)

300 400 500 600 700 8000

0.5

1

1.5

2

2.5

3x 10

5

Temperature (K)

Conductivity (1/(ohm.m))

ConclusionsConclusions

This media may be developed in a number of ways

(i) As a perpendicular media

(ii) As a Heat assisted recording media (HARM)

(iii) Substitute Fe for Co – Increase Anisotropic field and decrease particle size.

(iv) Magnetic patterned media

M. Jollie1, C.D. Wright2, M Aziz2, J. Miles 3 , D.Choo 4

1Coventry University2University of Exeter3Dept Computer Science University of Manchester. 4Nanomagnetics Ltd Bristol.

Acknowledgements:Acknowledgements: