Status and Prospect on Heat Assisted Magnetic Recording (HAMR)

Transcription

1 Mark Re, Ganping Ju, Ed Gage, M. A. Seigler, W. A. Challener, K. Pelhos, N. Gokemeijer, D. Karns, B. Lu, Y. Peng, C. Peng, R. E. Rottmayer, X.M. Yang, H. Zhou, T. Rausch, X. Zhu, T. J Klemmer, X.W. Wu, J. Hohlfeld, L. Li, Y.T. Hsia, R.D. Hempstead Seagate Research Status and Prospect on Heat Assisted Magnetic Recording (HAMR) 12/06/2007 IDEMA

2 Outline for Heat Assisted Magnetic Recording Introduction HAMR systems Integrated head Challenge #1: Delivering the Light Challenge #2: Delivering the Field HAMR media and HDI HAMR recording results Future prospects Conclusion Page 2

3 Introduction Page 3

4 Insatiable demand for Digital Storage Storage has become personal Home Media Server Digital Video Recorder Digital Imaging Game Consoles Personal Computer HDTV w/ built-in DVR Handheld / Portable Automobile Page 4

5 Areal Density Growth Areal density growth calls for media with higher anisotropy and smaller grains (arb units) AD ~ 1/D p Co/Pt 10 nm MnAl CoPt Fe 14 Nd 2 B FePt FePd 200 Co 3 Pt CoPt 3 Co/Pd CoCrPt K u (10 7 erg/cm 3 ) YCo 5 Dieter Weller SmCo 5 2 Areal Denisty (bits/in ) Transistor Denisty (Number/Devic 1T 10G 100M 1M 10k Writability limitation due to limited B S from write pole materials CD Year DVD Blu Ray HD DVD HDD Areal Density Transistor Per Device Device Density Page 5

6 Heat Assisted Magnetic Recording Lower K u by temporarily raising Temperature Coercivity Drive Temperature Store Here Cool Media Heat Media Μ Μ Μ Μ Media Direction Available Head Field Write Here Temperature Page 6

7 HDD Recording Subsystem Components PFPE 5-15A a-ch x A Magnetic Layer AlMg 2 m m Slider Seagate Barracuda ATA II Disk Recording Head A 1m m Actuator Head Head Major Elements of HAMR HDD Recording Head Optical Delivery Magnetic Field Source Magneto-Resistive Reader Media Lubricant Overcoat Recording Layer Heatsink/Soft Underlayer Disk Substrate Mechanical Integration Servo Preamp Data Channel Page 7

8 HAMR System Grating Light Delivery Laser Module on E-blockE + Grating Coupler Wave Guide Reversed Slider Return Pole GMR Element Lubricant/Overcoat Write Pole Near Field Transducer Field Coil Heatsink Page 8 Magnetic Media

9 Integrated HAMR head: Challenge#1: Delivering the Light Challenge#2: Delivering the field Page 9

10 Recording Head - Optical Light Delivery Planar Solid Immersion Mirror Front View Coupling Grating Side View Core Cladding Cladding AlTiC 100 µm Media W. Challener et al., Optics Express 2005;13(18): Page 10

11 Optical Components Optical Waveguide Coupling Core I Alumina Spacer Tantala Core Grating Cladding Cladding AlTiC Bottom Cladding Alumina Sidewall Mirror Sidewall Reflectivity Bill Challener Page 11

12 Completed Optical Heads Grating 200 µm Control SIM Near Field Transducer Channel Waveguide Page 12

13 PSIM Near-field Intensity SNOM scans over focal plane at ABS. PSIM with tantala core layer sandwiched between two alumina cladding layers. At blue light (413 nm), FWHM focused spot size = 90 nm. Mode confinement 1 µm by 1 µm SIM Focusing Intensity (a. u.) Cross Track Position (nm) Page 13

14 Integrated HAMR head: Challenge#1: Delivering the Light Challenge#2: Delivering the field Page 14

15 Implementation of Ring head Gratings PSIM ABS Coils WG Core WG Cladding Magnetic Poles Substrate I Cladding Core Cladding I Page 15

16 Built Integrated HAMR Head: ABS View PSIM Top Pole(s) WG Core WG Cladding Return Pole Reader Jerry Baltzer Page 16

17 Optical Image & SNOM of ABS SIM Only Head 5000 ND19843, IY bar: J device, SIM-200 nm 1500 With ND26567, a Top IW bar: Pole L device, & CDSEM: Aperture corrupt nm Photon Counts nm FWHM = 124 nm FWHM = 140 nm Page 17

18 Integrated HAMR Head Crosssection ABS (after lapping) Top Cladding Main Pole Back Via Write Location Return Pole Light intensity and direction FIB by Kathy Trumbull Coils (x5) Core Bottom Cladding Page 18

19 HAMR media + HDI Page 19

20 HAMR Media High anisotropy media Overcoat and lubricant materials Thermal management via heat sink to obtain rapid cooling after writing doable; ps thermal relaxation times observed (J. Hohlfeld, G. Ju- Seagate) Specially designed heat sink and SUL Lubricant/Overcoat Recording Layer Interlayer Heat Sink /SUL Disk Substrate Recording at or near Curie Temperature HDI Issue: >770K interface temperatures Reducing Tc by doping, e.g. with Ni also reduces Ku (e.g. J.Thiele, JAP 91, 6995 (2002)) Page 20

21 Pump HAMR Media with thermal design - High anisotropy -Optimize thermal design - Vertical thermal flow -Lateral thermal diffusion -reduced T c ~ 650K FeNiPt Medium Temperature Heats and cools in ~ 150 ps Time (ps( ps) J. Hohlfeld G. Ju probe t pump-probe J.-U. Thiele et al, JAP Vol. 91, pg 6595, Page 21

22 Measuring Lateral Temperature Profiles Incident angle 405 nm 532 nm Medium Interlayer SUL/Heat sink Substrate Pump induced thermal profile measured as reflectivity changes by the XY scanning probe Signal is convolution of media thermal profile and probe profile Focus servo to ensure repeatable pump focusing and ability to spin disk Probe/Pump spot size ~280/380 nm Pump frequency up to 100 MHz (10 ns) Capable of supporting disks instead of samples Scanning pump-probe spin-stand (D. Karns) Page 22

23 Effects of HS thickness for model media no HS mag. media Interlayer Glass Media motion Velocity ~ 0 m/s With HS Proper thermally designed heat sink prevents preheating effects, very confined T- profiles mag. media Interlayer HS (600 nm) Glass D. Karns, B. Lu, G. Ju Media motion Velocity ~ 11 m/s note the different scale Page 23

24 HAMR HDI Zdol2000 won t work Zdol2000 Lube Desorption remaining weight(%) Zdol 2000 Advanced Lube 1 Advanced Lube 2 Lei Li Temperature (K) Page 24

25 HAMR recording and MFM Page 25

26 Spin Stand with Light Delivery Mirror Detector Steering Mirror Optical Fiber HAMR HGA BS Lens Disk Slider Steering Mirror Mirror Page 26

27 Magnetic Field Optical Spot Registration Blue PSIM Optical Spot with FWHM = 90 nm Rapid Cooling Limits Thermal Spread, FWHM thermal ~ 130 nm Power Chosen for Tmax = 650 K Optical Intensity (a.u.) Clean up plot, black X (nm) Optical Spot Temp (K) Media Temperature (K) Page 27

28 Optical Spot and Media Short-time Coercivity 1.25 Optical Spot Optical Intensity (a.u.) ns (Oe) ns (Oe) Media X (nm) Page 28

29 Optical Intensity (a.u.) Recording Point Media Optical Spot 1ns (Oe) Hsw (Oe) X (nm) Recording Point Pole How to optimize recording point which is a function of Magnetic field (pole position, writer design, write current) Thermal spot (optical spot, power, media thermal properties) Media magnetic properties (Hc, Curie temperature) 0 H (Oe) Pole 75 nm from center of optical spot Write gradient (thermal and magnetic field) is not optimum Recording point is under the pole => Light Blocked? Page 29

30 Wrote and read back data HAMR data was written and read back using an integrated HAMR read write head. The written track width was less than 150 nm. The physical magnetic pole width was ~300 nm. HAMR writing dominated by the thermal spot Cross Track ACSN (db) Pseudorandom Time Domain 10 8 signal PRBS bit# Cross track position (microns) Duane Karns Page 30

31 MFM of Non-HAMR & HAMR Tracks Fully Integrated HAMR Head Νοn ΗΑΜR ΗΑΜR HAMR Unique Media High Anisotropy Proper Heatsinking 120mΑ 70mΑ 70mΑ Tim Rausch, Xiaobin Zhu Page 31

32 MFM images of recorded tracks Fully Integrated HAMR Head HAMR Unique Media High Anisotropy Proper Heatsinking Both single tone and PRBS have been recorded Thermally dominated regime ~ Xiaobin Zhu, Tim Rausch Page 32

33 Future prospects Page 33

34 What is next: Near Field Transducers NFT to reduce the optical spot size. Aperture, bowtie, ridge WG, beaked antenna, 200 nm 100 nm Ridge Waveguide 37 nm 500 nm 500 nm 0 nm nm Optical Field in Media 500 nm 500 nm nm 200 nm 100 nm 0 nm -100 nm -200 nm Nano-Holes L.Yin et al., APL 85 (3), pp (2004). E. Popov, et al., Appl. Opt. 44, pp (2005). Rectangular Aperture Shi, et al, Jap. J. Appl. Phys. 41 (2002). Bowtie R. Grober, et al, APL 70, pp (1997). Hitachi - Beaked Antenna T. Matsumoto, et al, ISOM/ODS 05, (2005). Sharp - Smash Head S. Miyanishi INTERMAG (2005). Sony - SIL + Single Pole Head N. Kojima, et al, INTERMAG (2007). Page 34

35 HAMR + Bit Patterned Media Cross-sectional View Non-Magnetic Filler Magnetic Nano-particle(s) M M Page 35

36 Conclusion - Fabricated a thin film integrated HAMR head containing a reader, a magnetic writer, and an efficient blue light delivery system - Optical FWHM is ~ λ/4 - Created high anisotropy media with rapid cooling design - Built a spin stand with light delivery system -HAMR Recording was achieved signal -For productization, Near Field Transducer needs to be integrated PRBS bit# Page 36

37 Acknowledgements Thank you for the many contributions to this work: Seagate Research Heads Group, Media Group, Mechanical Integration Group, Servo Group, and Characterization Group INSIC HAMR ATP Joint Venture Partners This work was performed as part of the Information Storage Industry Consortium (INSIC) program in Heat Assisted Magnetic Recording (HAMR), with the support of the U. S. Department of Commerce, National Institute of Standards and Technology, Advanced Technology Program, Cooperative Agreement Number 70NANB1H3056 Page 37