The challenges for

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The challenges for
perpendicular
recording technology


Rob Hardeman

Seagate Technology (Ireland)


January 2006


© Seagate Confidential

It’s been around for a while …


1890’s Poulsen



1970’s Iwasaki



But now it’s really here..



2005 HGST, Seagate, Toshiba…..




(that’s in strictly alphabetical order





most would say Toshiba won but….)


January 2006


© Seagate Confidential

Current Reality


HGST

Hitachi lays groundwork for 20
-
GB Microdrive with century
-
old technology


As the resolution of digital images keeps growing, it proves a challenge for storage devices to keep up with the pace. As cur
ren
t
technology for harddisk recording reaches its limits, a revolutionary step is needed. A new technolgy, "
Perpendicular Recording
"
has been waiting in the wings for some time now, but apparently proved difficult to implement. Hitachi has now demonstrated a

data density at 230 gigabits per square inch using this new technology...

Company Demonstrates 230 Gigabit Per Square Inch Data Density on Perpendicular Recording; Industry Luminaries Make History
as Part of Worldwide Field Test Program


TOKYO


April 4, 2005


Hitachi Global Storage Technologies is today announcing new advancements to a 100
-
year
-
old magnetic
recording technology that will set the stage for ultra
-
high capacities such as a 20
-
gigabyte* Microdrive or a one terabyte 3.5
-
i
nch
hard drive.


To achieve this, Hitachi has demonstrated the industry's highest data density at 230 gigabits per square inch (Gb/in2) on
perpendicular recording. Hitachi believes 230 Gb/in2, which represents a doubling of today's highest longitudinal recording
densities, will be implemented in commercial hard drive products in 2007. When fully realized over the next 5
-
7 years,
perpendicular recording could enable a 10
-
fold increase in data densities over longitudinal recording, paving the way for new
heights in capacity such as a 60 GB one
-
inch drive.


"We are at the cusp of the most significant hard drive technology transition of the past decade, and it's one that holds so m
uch

promise for the hard drive and consumer electronics industries," said Jun Naruse, CEO, Hitachi Global Storage Technologies. "
As
the biggest supplier of small
-
form
-
factor hard drives, 2.5
-
inch and below, consumers' demand for storing more data on smaller
devices has provided a strong impetus for us to pursue perpendicular recording with a greater sense of urgency."


While the transition to perpendicular recording will start as early as the next product generation, Hitachi believes the true

po
tential
will be realized in the 200+ Gb/in2 range


the point of technology maturation when meaningful advancements in storage capacity
will ensure full
-
scale adoption of perpendicular recording technology.



"The health of this industry over the next 5
-
10 years is critically tied to the successful implementation and transition to
perpendicular recording technology," said Jim Porter, hard drive industry analyst and historian, owner of DISK/TREND. "Hitach
i i
s
taking a responsible approach in assuring that it proceeds smoothly with extensive testing programs."


January 2006


© Seagate Confidential

HGST website


excellent…


January 2006


© Seagate Confidential

Current Reality
-

Seagate

SEAGATE INTRODUCES WORLD'S
FIRST 2.5
-
INCH PERPENDICULAR
RECORDING HARD DRIVE;

SCOTTS VALLEY, Calif.

08 June 2005




Seagate 160GB 2.5
-
Inch Notebook Drive Sets
New Capacity Benchmark

Breaking new ground in the mobile
computing market, Seagate Technology
(NYSE:STX) today announced the world's
first 2.5
-
inch disc drive built on perpendicular
recording technology
-

a 160GB notebook PC
giant with 25 percent more capacity than the
largest capacity notebook drive currently
available. This expansion of Seagate's family
of Momentus notebook drives further closes
the capacity and performance gap between
desktop and notebook PC hard drives as
more users replace aging desktop systems
with fast, high
-
capacity notebook computers



January 2006


© Seagate Confidential

Current Reality
-

Toshiba

TOSHIBA CROSSES FINISH LINE FIRST, DELIVERING FIRST HARD
DISK DRIVE

BASED ON PERPENDICULAR MAGNETIC RECORDING

New era of HDD technology begins with

Toshiba’s shipment of 40GB 1.8
-
inch
PMR drives

Irvine, Calif, Aug. 16, 2005


Toshiba Storage Device Division (SDD), the
industry pioneer in

small form factor hard disk drives (HDDs), today announced
shipment of the world's first HDD

based on perpendicular magnetic recording
(PMR). The new 1.8
-
inch HDD, used primarily in

consumer electronics (CE)
devices, enables up to 10,000 songs or 25,000 photos on a single

40GB platter.

The MK4007GAL HDD 1.8
-
inch HDD packs 40GB on a single platter


the
largest

single
-
platter capacity1 yet achieved in the 1.8
-
inch form factor. This
breakthrough technology

sets new benchmarks for data density with the highest
areal density currently on the market at

206 megabits per square millimeter2 (133
gigabits per square inch). The 1.8
-
inch PMR

HDD is

now shipping in Toshiba’s
new Gigabeat F41, enabling the MP3 player to store up to 10,000

songs.

"Toshiba has started an exciting new frontier for the HDD industry by leading the
race to

achieve this revolutionary technology, which has been the industry’s aim
for more than 20

years," said Scott Maccabe, vice president, Toshiba Storage
Device Division. "PMR opens the

door to products we haven’t even begun to
imagine, by removing the technical barriers inherent

to packing more data on an
HDD. Providing greater storage capacity on mobile disk drives

allows Toshiba to
give system OEMs the tools they need for next
-
generation digital information

and entertainment devices."



January 2006


© Seagate Confidential

The items I’ll cover


or not..


Included


System and environmental aspects


Read and write processes and mechanisms


Details of the writer in the head



Media will be touched on but deferred to later speakers


Channels and coding will not be addressed


also to later
speakers.



January 2006


© Seagate Confidential

Fundamentals


Figure 1. a) Longitudinal recording with
magnetization in the plane of the
medium; b) perpendicular recording with
magnetization perpendicular to the plane
of the medium (Source: Komag.com);
and c) magnetoresistive sensing of a
storage bit's magnetization state in the
HDD medium (perpendicular recording).





The media has vertical magnetic
alignment not horizontal

The head and media are now
even more linked


half the head
is “in the media” as an image

The recording field is now from a
deep gap
-

not fringing



January 2006


© Seagate Confidential

Not quite so obvious


Signals of higher linear density are more thermally stable
for perpendicular

magnetic recording due to the reduced
demagnetizing field transition.

This is in sharp contrast to
longitudinal recording.



Measurements of overwrite now need to become
“reverse overwrite” i.e. Low frequency ovewriting high


The writing point is now the trailing edge of the write pole,
not the leading gap edge. The shape of the written
transition can be influenced by its geometry


Sensitivity to external magnetic fields


perhaps
surprisingly with higher coercivity “stable” media
-
is a
potential issue.


Small diameter discs are favoured for combination of
capacity, data rate and access time.


January 2006


© Seagate Confidential

Plus
ç
a change..


January 2006


© Seagate Confidential

Plus c’est la m
ê
me chose..


January 2006


© Seagate Confidential

Disc media


It’s not getting easier !


More layers


More control..

Solid State Technology

September, 2005


January 2006


© Seagate Confidential

Soft Underlayer (SUL)


Underlayer charactersistics of importance


Dynamics


Anisotropy


Interaction with recording layer


Thickness, cost, manufacturability…


January 2006


© Seagate Confidential

Head


reader


The existing GMR / TMR designs have adequate
sensitivity.


Reader fabrication methods are largely unchanged from
advanced longitudinal products.


January 2006


© Seagate Confidential

Erasure phenomena 1


same track

Q. Why doesn’t the
return pole write as
well ?



Return pole

Write pole

A.
It does


unless

It’s big enough

It’s shaped properly

(or it’s not there at all !!)

And

the write pole can
continue to write when
you don’t want it to


if it
has remanence..


January 2006


© Seagate Confidential

Erasure phenomena 2


side tracks

But making
trapezoidal
poles at less
than 100 nm
dimension and
with angular
accuracy of +/
-

a degree or so

is not the
easiest of
manufacturing
tasks…


January 2006


© Seagate Confidential

Head


writer


Materials


High moment materials are even more desirable


Low remanence is critical


High frequency properties essential


approaches using composites and laminates are active



Formation


additive or subtractive…





Okada et al


January 2006


© Seagate Confidential

Stray fields


Realised a decade ago but still under
-
appreciated…






Soft Underlayer and very small “probe” head as flux
concentrators


More efficient heads


greater problems…



January 2006


© Seagate Confidential

Signals & Noise


Because the reader is
mostly “on”


signals from
bits not transitions there is
much more low frequency
component.


This is a different
challenge for the channel
and optimal coding


January 2006


© Seagate Confidential

Summary


Perpendicular recording is here


the threshold is around
200 Gb/in2 as predicted for a while. Early applications are
in small form factor mobile devices.


System problems have been largely understood and
worked on for up to five years. A lot of knowledge is
directly transferable from longitudinal
BUT

a few items
thought to be subtleties have proved major obstacles


Capable media exist; SUL optimisation is still possible.


Manufacturing emphasis in the head has shifted from
reader sensitivity to writer formation.


Consumer confidence will grow with multiple suppliers
demonstrating reliability in service.



January 2006


© Seagate Confidential

And what’s next ?



Patterned/selected track media ?


Thermally assisted systems (HAMR) ?