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Recent Developments in Magnetic Recording Media

March 19, 2019 @ 6:30 pm - 8:30 pm PDT

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Location:   Western Digital,
1710 Automation Pkwy (Directions and Map)
San Jose, CA 95131 United States

Kumar Srinivasan

Technologist, Product Design Engineering at Western Digital


Due to capacity & price advantages, magnetic recording based hard-disk drives (HDD’s) remain the dominant auxiliary storage devices. Today, HDD’s with areal densities of ~1 Tbits/in2 are in commercial production. In the mid-2000’s, magnetic recording technology evolved from longitudinal recording media that had in-plane magnetization to perpendicular recording media that had out-of-plane magnetization. This shift meant that higher anisotropy materials were necessary to stabilize the grains against shape-based demagnetizing effects. In this regard, the invention of the CoCrPt-oxide material was a major breakthrough. Another major breakthrough was the introduction of the exchange-spring (ES) media. Originally proposed more than two decades back in permanent magnet design, the ES magnet was composed of both hard magnetic and soft magnetic phases, finely dispersed and in mutual contact with each other. Whereas the ES effect allowed permanent magnets to realize high energy products, the objective in PMR media design is rather different in that it allowed for improved media writability and switching field distributions, without sacrificing thermal stability. It is the ES concept along with other innovations, but not grain size scaling that have helped achieve areal densities of ~ 1Tbit/in2.

While PMR has successfully transformed the areal density perspective, its further advancement faces significant challenges due to the superparamagnetic limit. Heat-Assisted Magnetic Recording (HAMR) technology is one of the leading candidates to replace PMR. The structurally ordered L10 phase of FePt has among the highest known magnetocrystalline anisotropies. Due to the high anisotropy, the smallest thermally stable grain sizes can be of the order of 3 to 4nm. At these grain sizes, the FePt medium is capable of supporting several Tbits/in2 of data. However, the high anisotropy also means that the FePt medium has to be heated with a laser to above its Curie temperature, and the recording bits written during the re-freezing process. Briefly, this is the concept underlying HAMR technology.

This tutorial style talk will review progress made in recent years on current & future magnetic recording media technologies.


Kumar Srinivasan is currently an Engineering Technologist at Western Digital, working to advance magnetic recording media technology. He has extensive experience and expertise in process development, product design, advanced characterization and analysis on materials for data storage. He has authored/co-authored more than 40 peer-reviewed publications, one book chapter, been issued more than 15 patents/trade secrets and delivered invited talks at multiple forums such as MMM, MRS, IDEMA and IEEE. He is a Senior Member of the IEEE and has served on numerous conference organizing committees such as MMM and TMRC. Most recently, he was General Chair of TMRC in 2018. He holds M.S. & Ph.D. degrees in Materials Science & Engineering from Carnegie Mellon University and B.Tech in Metallurgical Engineering from the Indian Institute of Technology, Madras.


March 19, 2019
6:30 pm - 8:30 pm PDT


Western Digital
951 Sandisk Drive
Milpitas, CA 95035 United States
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