Transcript Slide 1
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 monodispersion 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 Our Solution A combination of reactive sputtering and Rapid Thermal Processing Technologies 2002 Longitudinal mono-disperse particulate media produced by Rapid Thermal Processing (RTP) of Co-Sputtered precurser material 2003 In response to direction that industry is moving the process has been modified to produce particulate perpendicular media 1. 3. 2. (a) Cobalt Nitride reactively co-sputtered with unreactive Platinum on to glass substrate to produce precursor layer. Precursor medium undergoes Rapid Thermal Processing in 8kWatt vacuum optical whenoff Power to Cobalt and Platinum targetsoven switched and thin Silicon Nitride protective overlayer Cobalt nitride disassociates with the release of deposited. 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 Ms 20W 40W 30W 500 500 500 0 0 0 50W 500 500 0 0 0 40W -500 0 500 C -500 0 500 C 500 -500 -500 0 500 C 30W 0.2 0 0 -0.2 -500 0.2 0 0 500 C -0.2 0 500 C 0 6 Applied Field / kOe 0 40W 500 C 50W 0.2 70W 60W 0 0 40W 500 C 0 500 C -6 -500 0.2 -500 0 500 C 0 k 20W 70W 60W 500 0.2 0.2 0 0 0.2 0 500 C 0 -0.2 500 C -0.2 0 500 C 0 500 C -0.2 0 -6 0 500 C -0.2 0 6 Applied Field / kOe Optimum sputtering powers to the Comuch and Pt targets determined by nature comparing theCoN in and out of plane It is found that although Pt sputters faster thanisCo the reactive of the deposition hysteresis loops as a that function of composition. The sequence shows theatresults of maintaining process determines the ratio of Co to Pt in thefollowing precursor films is optimised 1:1 when the 50W to the Co target whilst varying that to the Pt target between 20W and 70W. sputtering powers are near matched. -0.2 2500 70W CoPt CoPt3 40 60 80 40W Counts 500 20 2500 500 20 2500 40 500 20 40 60 30W 60 2 4 Hc / kOe 3 In Plane Out of Plane 2 1 0 30 45 60 Pt percentage in processed film 75 Faraday Rotation / Arb.units 450C 200oC 650oC 500C 300C -40 -40 -20 -20 0 20 0 40 20 -40 -20 40 0 Applied Field / kOe 20 40 M Mss 3000 3000 00 o 500 o 650 o 300 -3000 -3000 -6 -6 -3 -3 00 Applied Applied Field Field // kOe kOe 33 66 Counts 5000 650C 2500 0 20 40 60 80 100 5000 500C 2500 0 20 40 60 80 100 650C 500C 40 60 80 100 Normalised TAA 0.5 Normalised Noise Power 0.010 0 0.008 -0.5 0.006 -1.0 0.004 -1.5 0.002 -2.0 0 100 200 300 400 Linear Density /kfci 500 0 0 100 200 300 Linear Density / kfci 400 Hc / kOe 3 KV TB 25k 2 1 0 15.0 17.5 20.0 1/2 T /K 1/2 22.5 Normalised TAA M -0.2 0.5 -0.6 -1.0 0 100 200 300 400 0 Linear Density / kfci Normalised Noise Power 0.045 -0.5 0.030 0.015 0 0 2 4 Field / kOe 0 100 200 Linear Density / kfci 300 400 6 Probe Storage 5 Conductivity (1/(ohm.m)) 3 x 10 2.5 2 1.5 1 0.5 0 300 400 500 600 700 800 8 10 Temperature (K) Maximum Temperature (K) 1500 -1 100(Wm) -1 50(Wm) 1200 900 600 300 0 0 2 4 6 Voltage (V) 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 Acknowledgements: M. Jollie1, C.D. Wright2, M Aziz2, J. Miles 3 , D.Choo 4 1Coventry University 2University of Exeter 3Dept Computer Science University of Manchester. 4Nanomagnetics Ltd Bristol.