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/in 2 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/in 2 would be a mono- dispersion of highly anisotropic, non-interacting, single domain particles with T B < T C.

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

Longitudinal mono-disperse particulate media produced by Rapid Thermal Processing (RTP) of Co-Sputtered pre- curser material2003 In response to direction that industry is moving the process has been modified to produce particulate perpendicular media Our Solution A combination of reactive sputtering and Rapid Thermal 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

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.

Faraday Rotation / Arb.units Applied Field / kOe 200 o C 650 o C

Probe Storage

Conductivity (1/(ohm.m))

Conclusions 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. Jollie 1, C.D. Wright 2, M Aziz 2, J. Miles 3, D.Choo 4 1 Coventry University 2 University of Exeter 3 Dept Computer Science University of Manchester. 4 Nanomagnetics Ltd Bristol. Acknowledgements: