Pittsburgh Section

The Evolution and Revolutions in Disk Drive Recording

IEEE Magnetics Society

Distinguished Lecturer (I) for 2009: Dr Michael Mallary

IEEE Fellow, Seagate Technology

Abstract: Since 1956 the areal density of hard disk drives, HDDs, has increased by eight orders of

magnitude through a process of evolution punctuated by a number of important revolutions. The disk

evolved for three decades through many generations of painted gamma ferric oxide particulate media

with in plain orientation. During this time areal density was increased from 2 kilo-bits/inch2 (2kbpsi)

for IBM’s RAMAC to ~20Mbpsi .

The technology has seen a number of revolutions. In the mid 1980s the first (non-magnetic!)

revolution was a diamond like carbon over coat for media that is key to its durability. The next

revolution was the introduction of read sensors based on Giant Magneto-Resistive films with

improved sensitivity. HDD proceeded to evolve up to ~100 Gbpsi on this technology base.

By the mid 1990’s Prof. Stanley Charap of Carnegie Mellon University calculated that longitudinal

recording would start to experience thermal decay of the data at densities of ~40 Gbpsi. In response to

this impeding crisis, the Ultra-High Density Recording project was initiated by Prof. Mark Kryder

(CMU) under the National Storage Industry Consortium umbrella. The UHDR team established the

reality of the problem and proposed strategies to delay the crisis to ~100 Gbpsi. Key amongst these

was to increase tracks per inch faster than bits per inch.

The UHDR theory team also determined that magnetizing the media perpendicular to the disk could

extend magnetic recording by almost an order of magnitude beyond the thermal decay limit of

longitudinal recording. Perpendicular HDDs are now being shipped at ~300Gbpsi. Key head

innovations in achieving this density are the use of the the Shielded Pole writer invented by the author,

and the Tunneling Magneto-Resistive reader with an MR effect approaching 100%.

The 30-40% per year growth in areal density will soon drive perpendicular recording to its thermal

decay limit near 1 Tbpsi in demonstrations and less in products. Two revolutionary technologies are

being developed to deal with this. Heat Assisted Magnetic Recording will

allow high anisotropy media to be written at elevated temperatures thus

allowing for finer thermally stable grains to be written. Bit Patterned Media

will allow the recording of a bit on a single grain as compared to scores of

grains with unpatterned media. The promise and problems of these

technologies will be discussed in detail.

Bio: Michael Mallary is an IEEE Fellow and Distinguished Lecturer for 2009.

He received his S.B. degree in physics from the Massachusetts Institute of

Technology in 1966, and Ph.D. degree in Experimental High Energy Physic

from the California Institute of Technology, in 1972. He was a post doctoral

fellow at the Rutherford Laboratory for from 1972-1974 and an Assistant Professor of physics at

Northeastern University from 1974-1978. There he participated in an experiment at Fermi Laboratory

that produced early evidence for the fifth quark using a 300 ton solid iron magnet. From 1978 to 1980

he worked at the Magnetic Corporation of America designing large superconducting magnets for

MHD, MRI, energy storage and magnetic separation. In 1980 he joined the Digital Equipment

Corporations effort to produce thin film heads for disk drive recording as a head modeler and designer.

Here he invented the Shielded Pole perpendicular recording head which has demonstrated superior

performance over the conventional monopole head and is now in very disk drive shipped today. He

also invented the Diamond inductive head which doubles the effective number of turns. In addition he

has contributed to the theory of: flux conduction in thin film heads at high frequency; low bit aspect

ratios for high density in the thermal decay limit; and tilted write fields for improved switching. His

publications and patents have significantly advanced the field of magnetic recording. He is presently

working on Heat Assisted Magnetic Recording, Shingle Recording and 2 Photon Recording at the

Seagate Technology Research Center in Pittsburgh. He has authored and co-authored 67 issued patents

and 52 publications including “Our Improbable Universe” (ISBN 1-56858-301-X).

Place: Seagate Research Center Auditorium

Date: Monday, Jan. 12th, 2009

Time: Social (w/ Lunch served): 11:45AM, Technical Program: 12:15 PM

This meeting will be of particular interest to the members who belong to IEEE Magnetics Society, and

others are also very welcome. Please RSVP to Ganping.Ju@Seagate.com to help us prepare the lunch.

Directions to Seagate Research Center:

Seagate Research Center is located at 1251 Waterfront Place, Pittsburgh, in the Strip District, across

from the Heinz History Center and next to the Convention Center.