RECORDING HEAD
TECHNOLOGY BASIC
School of Mechanical Engineering
Institute of Engineering
Suranaree University of Technology
Outline
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Magnetic and Magnetism
History of Magnetic Recording
Digital Data Encoding and Decoding
HDD Write Head Technology
HDD Read Head and MR Technology
HDD Recording Material
Introduction to Head Fabrications
Introduction to HDD Head Test
HDD Component
HDD Recording Head
Magnetism
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Magnetism is one of the phenomena by
which materials exert an attractive or
repulsive forces on other materials.
Some well known materials that exhibit
easily detectable magnetic properties are
nickel, iron, some steels, and the mineral
magnetite.
Magnetism
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The ancient Greeks, originally those near
the city of Magnesia, and also the early
Chinese knew about strange and rare
stones with the power to attract iron.
Chinese found that a steel needle stroked
with such a "lodestone" became
"magnetic" when freely suspended,
pointed north-south.
Around 1600 William Gilbert, proposed an
explanation: the Earth itself was a giant
magnet, with its magnetic poles some
distance away from its geographic ones
Lodestone
Magnetism
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Until 1821, only one kind of magnetism was
known, the one produced by iron magnets.
Hans Christian Oersted noticed that the current
caused a nearby compass needle to move.
Andre-Marie Ampere, who concluded that the
nature of magnetism was quite different from
what everyone had believed.
It was basically a force between electric currents:
two parallel currents in the same direction attract,
in opposite directions repel.
Magnetic Dipoles
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Normally, magnetic fields are seen as
dipoles, having a "South pole" and a "North
pole";
A magnetic field contains energy, and
physical systems stabilize into the
configuration with the lowest energy.
The magnetic energy, so-called “flux” flows
from the north pole to the south pole.
Magnetic Dipoles
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Magnetic dipoles result on the atomic scale
from the two kinds of movement of
electrons.
First: the orbital motion of the electron
around the nucleus.
Second: source of electronic magnetic
moment is due to a quantum mechanical
property called the “spin dipole” magnetic
moment
Magnetic Field
Type of Magnet
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Permanent Magnets
Electromagnets
Permanent magnets
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A few elements -- especially iron, cobalt, and
nickel -- are ferromagnetic at room temperature.
Every ferromagnetic has its own individual
temperature, called the Curie temperature, or
Curie point,
A long bar magnet has a north pole at one end
and a south pole at the other. Near either end the
magnetic field falls off inversely with the square
of the distance from that pole.
For a magnet of any shape, at distances large
compared to its size, the strength of the
magnetic field falls off inversely with the cube of
the distance from the magnet's centre.
Classification of Magnetic
Materials
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Diamagnetism
Paramagnetism
Ferromagnetism
Antiferromagnetism
Ferrimagnetism
Diamagnetism
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In a diamagnetic material the atoms have no net
magnetic moment when there is no applied field.
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Under the applied field (H) the spinning
electrons produces a magnetisation (M) in the
opposite direction to that of the applied field
Paramagnetism
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In paramagnetism materials each atom
has a magnetic moment which is
randomly oriented as a result of thermal
agitation.
The magnetic field creates a slight
alignment of these moments and hence a
low magnetisation in the same direction
as the applied field.
Ferromagnetism
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Ferromagnetism is only possible when
atoms are arranged in a lattice and the
atomic magnetic moments can interact to
align parallel to each other.
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Only Fe, Co and Ni are ferromagnetic at
and above room temperature
Antiferromagnetism
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Antiferromagnetic materials are very similar to
ferromagnetic materials but the exchange
interaction between neighboring atoms leads to
the anti-parallel alignment of the atomic
magnetic moments.
Ferrimagnetism
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Ferrimagnetism is only observed in
compounds, which have more complex
crystal structures than pure elements
Classification of Magnetic
Materials
Electromagnet
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An electromagnet is a wire that has been
coiled into one or more loops, known as a
solenoid.
When electric current flows through the wire,
a magnetic field is generated.
The more loops of wire, the greater the
cross-section of each loop, and the greater
the current passing through the wire, the
stronger the field.
Uses for electromagnets include particle
accelerators, electric motors, etc
The Orientation of Magnet
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The orientation of this effective magnet is
determined via the right hand rule.
Magnetic Phenomena
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An electric current produces a magnetic
field.
Some materials are easily magnetized
when placed in a weak magnetic field.
When the field is turned off, the material
rapidly demagnetizes. These are called
"Soft Magnetic Materials."
Magnetic Phenomena
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In some magnetically soft materials the electrical
resistance changes when the material is
magnetized. The resistance goes back to its
original value when the magnetizing field is
turned off. This is called "Magneto-Resistance"
or the MR Effect.
Certain other materials are magnetized with
difficulty but once magnetized, they retain their
magnetization when the field is turned off. These
are called "Hard Magnetic Materials" or
"Permanent Magnets."
HISTORY OF MAGNETIC
RECORDERS
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In 1888, Oberlin Smith originated the idea
of using permanent magnetic impressions
to record sounds.
In 1900, Vladeniar Poulsen demonstrated
a Telegraphone. It was a device that
recorded sounds onto a steel wire.
Although everyone thought it was a great
idea, they didn't think it would succeed
since you had to use an earphone to hear
what was recorded.
HISTORY OF MAGNETIC RECORDERS
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Until 1935, all magnetic recording was on steel
wire.
Then, at the 1935 German Annual Radio
Exposition in Berlin, Fritz Pfleumer
demonstrated his Magnetophone. It used a
cellulose acetate tape coated with soft iron
powder.
The Magnetophone and its "paper" tapes were
used until 1947 when the 3M Company
introduced the first plastic-based magnetic tape.
HISTORY OF MAGNETIC RECORDERS
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In 1956, IBM introduced the next major
contribution to magnetic recording - the
hard disk drive. The disk was a 24-inch
solid metal platter and stored 4.4
megabytes of information.
Later, in 1963, IBM reduced the platter size
and introduced a 14-inch hard disk drive.
HISTORY OF MAGNETIC RECORDERS
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In 1971, 3M Company introduced the first
1/4-inch magnetic tape cartridge and tape
drive.
In that same year, IBM invented the 8-inch
floppy disk and disk drive. It used a
flexible 8-inch platter of the same material
as magnetic tape.
In 1980, a little-known company named
Seagate Technology invented the 5-1/4inch floppy disk drive.
PREREQUISITES FOR
MAGNETIC RECORDING
 Input
Signal
 Recording Medium
 Magnetic Head
Input Signal
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An input signal can come from a
microphone, a radio receiver, electrical
device, or any other source that's capable
of producing a recordable signal.
Some input signals can be recorded
immediately, but some must be processed
first.
This processing is needed when an input
signal is weak, or is out of the Frequency
response range of the recorder.
Recording Medium
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A recording medium is any material that
has the ability to become magnetized, in
varying amounts, in small sections along
its entire length.
Some examples of this are magnetic tape
and magnetic disks
Magnetic Heads
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Magnetic heads are the transducers that
convert the electrical input signal into the
magnetic that are stored on a recording
medium.
Magnetic heads do 3 different things.
Transfer signal onto the recording medium.
Recover signal from the recording medium.
Remove signal off the recording medium.
Writing Magnetic Data
Reading Magnetic Data
Integrating the Write/Read Heads
HDD Data Encode and Decode
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Digital information is a stream of ones
and zeros.
Hard disks store information in the form
of magnetic pulses.
In order for the PC's data to be stored on
the hard disk, therefore, it must be
converted to magnetic information.
When it is read from the disk, it must be
converted back to digital information.
HDD Data Encode and Decode
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Magnetic information on the disk consists
of a stream of very small magnetic fields.
Information is stored on the hard disk by
encoding information into a series of
magnetic fields.
This is done by placing the magnetic
fields in one of two polarities: either N-S,
or S-N
HDD Data Encode and Decode
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Although it is conceptually simple to
match "0 and 1" digital information to “NS” and “S-N” magnetic fields.
The reality is much more complex: a 1-to1 correspondence is not possible, and
special techniques must be employed to
ensure that the data is written and read
correctly.
Technical Requirements
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Fields vs. Reversals
Synchronization
Field Separation
Fields vs. Reversals
 Read/write heads are designed not to
measure the actual polarity of the
magnetic fields, but rather flux
reversals.
 Flux reversals occur when the head
moves from an area that has N-S
polarity to S-N, or vice-versa.
Fields vs. Reversals
 The reason the heads are designed based
on flux reversals instead of absolute
magnetic field, is that reversals are easier
to measure.
 The encoding of data must be done based
on flux reversals, and not the contents of
the individual fields.
Synchronization:
 Another consideration in the encoding of
data is the necessity of using some sort
of method of indicating where one bit
ends and another begins.
 Even if we could use one polarity to
represent a "one" and another to
represent a "zero", what would happen if
we needed to encode on the disk a stream
of 1,000 consecutive zeros?
Field Separation
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Although we can conceptually think of
putting 1000 tiny N-S pole magnets in a
row one after the other. They are additive.
Aligning 1000 small magnetic fields near
each other would create one large
magnetic field, 1000 times the size and
strength of the individual components.
Data Encoding
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We must encode using flux reversals, not
absolute fields.
We must keep the number of consecutive
fields of same polarity to a minimum.
To keep track of which bit is where, some
sort of clock synchronization must be
added to the encoding sequence.
Data Encoding
Media Limitation
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Each linear inch of space on a track can
only store so many flux reversals.
We need to use some flux reversals to
provide clock synchronization, these are
not available for data.
A prime goal of data encoding methods is
therefore to decrease the number of flux
reversals used for clocking relative to the
number used for real data.
Media Limitation
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Over time, better methods that used fewer
flux reversals to encode the same amount
of information.
Hardware technology strives to allow
more bits to be stored in the same area by
allowing more flux reversals per linear
inch of track.
Encoding methods strive to allow more
bits to be stored by allowing more bits to
be encoded (on average) per flux reversal.
Data Encode/Decode Methods
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Frequency Modulation (FM)
Modified Frequency Modulation (MFM)
Run Length Limited (RLL)
Partial Response, Maximum Likelihood
(PRML)
Extended PRML (EPRML)
Frequency Modulation (FM)
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This is a simple scheme, where a one is
recorded as two consecutive flux
reversals, and a zero is recorded as a flux
reversal followed by no flux reversal.
This can also be thought of as follows: a
flux reversal is made at the start of each
bit to represent the clock, and then an
additional reversal is added in the middle
of each bit for a one, while the additional
reversal is omitted for a zero.
FM
Bit Pattern
Encoding
Pattern
Flux Reversals Per Bit
Bit Pattern
Commonality In
Random Bit Stream
0
RN
1
50%
1
RR
2
50%
1.5
100%
Weighted Average
FM
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The name "frequency modulation" comes from
the fact that the number of reversals is doubled
for ones compared to that for zeros.
A byte of zeroes would be encoded as
"RNRNRNRNRN…",
A byte of all ones would be "RRRRRRR……“
The ones have double the frequency of reversals
compared to the zeros; hence frequency
modulation (meaning, changing frequency based
on data value).
FM
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FM is very wasteful:
Each bit requires two flux reversal
positions, with a flux reversal being added
for clocking every bit.
Compared to more advanced encoding
methods that try to reduce the number of
clocking reversals, FM requires double (or
more) the number of reversals for the
same amount of data.
Modified Frequency Modulation
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MFM improves on FM by reducing the number of
flux reversals inserted just for the clock.
Instead of inserting a clock reversal at the start of
every bit, one is inserted only between
consecutive zeros.
When a 1 is involved there is already a reversal (in
the middle of the bit) so additional clocking
reversals are not needed.
When a zero is preceded by a 1, we similarly know
there was recently a reversal and another is not
needed. Only long strings of zeros have to be
"broken up" by adding clocking reversals.
MFM
Bit Pattern
Encoding
Pattern
Flux Reversals
Per Bit
Bit Pattern
Commonality In
Random Bit Stream
0 (preceded by 0)
RN
1
25%
0 (preceded by 1)
NN
0
25%
1
NR
1
50%
0.75
100%
Weighted Average
MFM
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Since the average number of reversals
per bit is half that of FM, the clock
frequency of the encoding pattern can
be doubled, allowing for approximately
double the storage capacity of FM.
MFM
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MFM encoding was used on the earliest
hard disks, and also on floppy disks.
Since the MFM method about doubles the
capacity of floppy disks compared to
earlier FM ones, these disks were called
"double density".
In fact, MFM is still the standard that is
used for floppy disks today.
For hard disks it was replaced by the
more efficient RLL methods.
Run Length Limited
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An improvement on the MFM encoding is
Run Length Limited or RLL.
This is a more sophisticated coding
technique, or more correctly stated,
"family" of techniques.
RLL is a family of techniques because
there are two primary parameters that
define how RLL works, and therefore,
there are several different variations.
RLL
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RLL takes MFM technique one step
further.
It considers groups of several bits instead
of encoding one bit at a time.
The idea is to mix clock and data flux
reversals to allow for even denser packing
of encoded data, to improve efficiency.
The two parameters that define RLL are
the run length and the run limit (and
hence the name).
RLL
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The word "run" here refers to a sequence
of spaces in the output data stream
without flux reversals.
The run length is the minimum spacing
between flux reversals, and the run limit is
the maximum spacing between them.
As mentioned before, the amount of time
between reversals cannot be too large or
the read head can get out of sync and
lose track of which bit is where.
RLL
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The particular variety of RLL used on a drive
is expressed as "RLL (X,Y)" or "X,Y RLL"
X is the run length and Y is the run limit.
The most commonly used types of RLL in
hard drives are "RLL (1,7)", and "RLL (2,7)"
Consider the spacing of potential flux
reversals in the encoded magnetic stream. In
the case of "2,7", this means that the
smallest number of "spaces" between flux
reversals is 2, and the largest number is 7.
RLL
Bit Pattern
Encoding
Pattern
Flux Reversals
Per Bit
Bit Pattern
Commonality In
Random Bit Stream
11
RNNN
1/2
25%
10
NRNN
1/2
25%
011
NNRNNN
1/3
12.5%
010
RNNRNN
2/3
12.5%
000
NNNRNN
1/3
12.5%
0010
NNRNNRNN
2/4
6.25%
0011
NNNNRNNN
1/4
6.25%
0.4635
100%
Weighted Average
RLL
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If we were writing the byte "10001111" (8Fh),
this would be matched as "10-0011-11" and
encoded as "NRNN-NNNNRNNN-RNNN".
Since every pattern above ends in "NN", the
minimum distance between reversals is two.
The maximum distance would be achieved
with consecutive "0011" patterns, resulting
in "NNNNRNNN-NNNNRNNN" or seven nonreversals between reversals. Thus, RLL (2,7).
RLL
Peak Detection
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Standard read circuits work by detecting flux
reversals and interpreting them based on the
encoding method.
The controller converts the signal to digital
information by analyzing, synchronized to
internal clock, and looking for small voltage
spikes in the signal that represent flux
reversals.
This traditional method of reading and
interpreting hard disk data is called peak
detection.
Peak Detection
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The circuitry scans the data read from the
disk looking for positive or negative "spikes"
that represent flux reversals.
Peak Detection
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This method works fine as long as the
peaks are large enough to be picked out
from the background noise of the signal.
As data density increases, the flux
reversals are packed more tightly and the
signal becomes much more difficult to
analyze.
This can potentially cause bits to be
misread from the disk.
Peak Detection
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To take the next step up in density, the
magnetic fields must be made weaker.
This reduces interference, but causes
peak detection to be much more difficult.
At some point it becomes very hard for
the circuitry to actually tell where the flux
reversals are.
PRML
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To combat this problem a new method
was developed.
This technology, called partial response,
maximum likelihood or PRML, changes
entirely the way that the signal is read and
decoded from the surface of the disk.
PRML
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PRML employs sophisticated digital signal
sampling, processing and detection
algorithms to:
Manipulate the analog data stream coming
from the disk (the "partial response"
component)
Determine the most likely sequence of bits
this represents ("maximum likelihood")
PRML
Extended PRML (EPRML)
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An evolutionary improvement on the
PRML is extended partial response,
maximum likelihood, or EPRML.
This advance was the result of engineers
tweaking the basic PRML design to
improve its performance.
EPRML devices work in a similar way to
PRML.
They just use better algorithms and
signal-processing circuits.
EPRML
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The chief benefit of using EPRML is that
due to its higher performance, areal
density can be increased without
increasing the error rate. Claims
regarding this increase range from around
20% to as much as 70%, compared to
"regular" PRML.
EPRML has now been widely adopted in
the hard disk industry and is replacing
PRML on new drives.
Recording Head Technology
Recording Head Technologies
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Ferrite Heads
Metal-In-Gap (MIG) Heads
Thin Film (TF) Heads
(Anisotropic) Magnetoresistive (MR/AMR)
Heads
Giant Magnetoresistive (GMR) Heads
Colossal Magnetoresistive (CMR) Heads
TMR Heads
Ferrite Heads
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The oldest head design is also the simplest
conceptually.
When writing, the current in the coil creates
a polarized magnetic field in the gap
between the poles of the core, which
magnetizes the platter.
When the direction of the current is
reversed, the opposite polarity magnetic
field is created.
For reading, the process is reversed.
Ferrite Heads
Metal-In-Gap Heads
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The improvement of ferrite head design was
Metal-In-Gap heads.
They are essentially the same design, but
add a special metallic alloy in the head.
This change greatly increases its
magnetization capabilities, allowing MIG
heads to be used with higher density media.
They are usually found in PC hard disks of
about 50 MB to 100 MB.
Thin Film Head
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Thin Film (TF) heads--also called thin film
inductive (TFI)--are a totally different
design from ferrite or MIG heads.
They are so named because of how they
are manufactured.
TF heads are made using a
photolithographic process similar to how
processors are made.
Thin Film Head
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Thin film heads are capable of being used on
much higher-density drives and with much
smaller floating heights.
They were used in many PC HDD in the late
1980s to mid 1990s, usually up to 1000 MB
capacity range.
Thin Film Head Structure
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A thin film head structure consists of 20
material layers with patterns for each
layer defined by photolithography and
either additive processing
(electroplating, liftoff masking) or
subtractive processing (ion milling, wet
etching, reactive ion etching, chemical
mechanical processing).
Thin Film Head Structure
Critical Thin Film Head Features
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Two critical features in the thin film head, the
width of the read sensor (MRw) and the width of
the write pole tip (P2w), determine areal density
performance.
The lithography techniques for the MR sensor
are comparable to gate requirements in
integrated circuits. The lithography processing
for the write pole tip can be compared with the
interconnect processing strategy in the
integrated circuit.
AMR Head
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The newest type of technology commonly
used in read/write heads is much more of
a radical change to the way the read/write
head works.
While conventional ferrite or thin film
heads work on the basis of inducing a
current in the wire of the read head in the
presence of a magnetic field,
magnetoresistive (MR) heads use a
different principle entirely to read the
disk.
AMR Head
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An MR head employs a special conductive
material that changes its resistance in the
presence of a magnetic field.
As the head passes over the surface of
the disk, this material changes resistance
as the magnetic fields change
corresponding to the stored patterns on
the disk.
AMR Head
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The MR head is not generating a current directly
the way standard heads do, it is several times
more sensitive to magnetic flux changes in the
media.
This allows the use of weaker written signals,
which lets the bits be spaced closer together
without interfering with each other, improving
capacity by a large amount.
AMR Head
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MR technology is used for reading the disk
only. For writing, a separate standard thin-film
head is used.
This splitting of chores into one head for
reading and another for writing has additional
advantages.
Traditional heads that do both reading and
writing are an exercise in tradeoffs, because
many of the improvements that would make
the head read more efficiently would make it
write less efficiently, and vice-versa.
AMR Head
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First introduced in 1991 by IBM but not
used widely until several years later, MR
heads were one of the key inventions that
led to the creation of hard disks over 1 GB.
Despite the increased cost of MR heads,
they have now totally replaced thin film
heads.
AMR Head
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Even MR heads however have a limit in
terms of how much areal density they can
handle.
The successor to MR is GMR heads,
named for the giant magnetoresistive
effect.
They are similar in basic concept to MR
heads but are more advanced
GMR Head
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First discovered in the late 1980s by two
European researchers, Peter Gruenberg
and Albert Fert, who were working
independently.
Working with large magnetic fields and
thin layers of various magnetic materials,
they noticed very large resistance
changes when these materials were
subjected to magnetic fields.
GMR Head
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IBM developed GMR into a commercial
product by experimenting with thousands
of different materials and methods.
A key advance was the discovery that the
GMR effect would work on multilayers of
materials deposited by sputtering.
By December 1997, IBM had introduced
its first hard disk product using GMR
heads.
GMR Head Technology
Evolution of R/W Head
Giant magnetoresistive effect
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Giant Magnetoresistance (GMR) is a
quantum mechanical effect observed in
thin film structures composed of
alternating ferromagnetic and
nonmagnetic metal layers.
The effect manifests itself as a significant
decrease in resistance to a lower level of
resistance when sensing different
magnetic field.
GMR Technology
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The spin of the electrons of the
nonmagnetic metal align parallel or
antiparallel with an applied magnetic field
in equal numbers, and therefore suffer
less magnetic scattering when the
magnetizations of the ferromagnetic
layers are parallel.
GMR
Types of GMR
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Multilayer GMR
Granular GMR
Spin valve GMR
Multilayer GMR
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Two or more ferromagnetic layers are
separated by a very thin (about 1 nm) nonferromagnetic spacer (e.g. Fe/Cr/Fe).
The GMR effect was first observed in the
multilayer configuration, with much early
research into GMR focusing on multilayer
stacks of 10 or more layers.
Granular GMR
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Granular GMR is an effect that occurs in
solid precipitates of a magnetic material
in a non-magnetic matrix.
In practice, granular GMR is only
observed in matrices of copper containing
cobalt granules.
Granular GMR materials have not been
able to produce the high GMR ratios
found in the multilayer counterparts.
Spin valve GMR
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Two ferromagnetic layers are separated by a thin
(about 3 nm) non-ferromagnetic spacer.
If the coercive fields of the two ferromagnetic
electrodes are different it is possible to switch
them independently.
Therefore, parallel and anti-parallel alignment
can be achieved, and normally the resistance is
again higher in the anti-parallel case. This device
is sometimes also called spin-valve.
Spin-valve GMR is the configuration that is most
industrially useful, and is the configuration used
in hard drives.
Spin valve GMR
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When the head passes
over a magnetic field of
one polarity (say, "0"), the
free layer electrons turn
to be aligned with those
of the pinned layer; this
creates a lower resistance
in the entire head
structure.
Spin valve GMR
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When the head passes
over a magnetic field of
the opposite polarity
("1"), the electrons in the
free layer rotate so that
they are not aligned with
those of the pinned
layer. This causes an
increase in the
resistance of the overall
structure.
GMR head materials




Free Layer
Spacer
Pinned Layer
Exchange Layer
Free Layer:

This is the sensing layer, made of a
nickel-iron alloy, and is passed over the
surface of the data bits to be read.
Spacer:

This layer is nonmagnetic, typically made
from copper, and is placed between the
free and pinned layers to separate them
magnetically.
Pinned Layer:

This layer of cobalt material is held in a
fixed magnetic orientation by virtue of its
adjacency to the exchange layer.
Exchange Layer:

This layer is made of an
"antiferromagnetic" material, typically
constructed from iron and manganese,
and fixes the pinned layer's magnetic
orientation.
AMR VS GMR



AMR heads typically exhibit a resistance
change of about 2%, for GMR heads this
is anywhere from 5% to 8%.
GMR heads can detect much weaker and
smaller signals, which is increasing areal
density, capacity and performance.
GMR are much less subject to noise and
interference because of their increased
sensitivity, and they can be made smaller
and lighter than MR heads
TMR Phenomena


The magneto resistance in a tunnel-valve
originates from a change in tunneling
probability dependent on the relative
magnetic orientation of two ferromagnetic
layers.
The response of a free ferromagnetic layer
to the magnetic field of the storage media
results in a change of electrical resistance
in the tunnel-valve sensor.
TMR
Spin-Valve VS Tunnel Valve
TMR Read Head
Perpendicular Recording



One of the key challenges facing the hard
drive industry is overcoming the
constraints imposed by the
superparamagnetic effect.
Which occurs when the microscopic
magnetic grains on the disk become so
tiny that ambient temperature can reverse
their magnetic orientations.
The result is that the bit is erased and,
thus, data is lost.
Perpendicular Recording
PMR Platter Structure
PMR Response
Today PMR HDD





2006 Seagate: the world's first 3.5 inch
Cheetah 15K 300GB storage.
2006 Toshiba: 40GB MK4007GAL 1.8” HDD
2006 Fujitsu: 160GB MHW2160BH 2.5" HDD
2006 Seagate: Barracuda 7200.10, 750 GB
3.5” HDD.
2007 Hitachi announced the first 1 Terabyte
Hard Drive
PMR HDD
HDD HEAD Fabrications
Wafer fabrication processes

Wafer is the common word of raw
material for ICs manufacturing.
Usually thin, round and silicon crystal
in diameter 150, 200 and 300 mm. The
wafer fabrication is normally operated
under vacuum and cleanroom.
1. Preparation of wafer media
2. Wafer processing
Preparation of wafer media

Wafer media is fabricated as substrate of
next processes.
1.
2.
3.
4.
5.
6.
Crystal growth and wafer slicing
Thickness sorting
Lapping & etching
Thickness & flatness checking
Polishing
Final Testing
Wafer processing


Photolithography
Additive processing


Subtractive processing



Thin film technology
Wet etching
Dry etching (Ion milling, Plasma etching,
Reactive ion etching)
Modifying (dopant)


Diffusion
Ion implantation
Wafer
Basic of head slider fabrication



Slider fabrication is the process of parting
wafer containing thousands of recording
heads into a form factor called slider.
Each slider embodying one recording head.
The flying height of less that 10 nm has
mandated the use of the most advanced
micromachining and vacuum technologies to
deliver the extreme mechanical
sophistications required in the sliders.
Basic of head slider fabrication
Basic of head slider fabrication
Fly Height?
Basic of head slider fabrication





Thin and polish wafer by lapping
Bonded the entire wafer to a platform
Wafer slicing into row of slider by multiblade
The rows are processed in various
ways, including lapping and ion milling
to form air bearing surface (ABS)
Dividing to each slide
Basic of head slider fabrication
Basic of head slider fabrication
HGA - HSA
Basic of media fabrication
Glass substrate




highly planar
low defect
Smoothness
Suit modulus which yields stable
mechanical properties in the drive
Glass substrate fabrication




Design of Glass Composition
Glass Melting and Molding
Machining Brittle Materials
Precision Cleaning
Glass Substrates Manufacturing
Magnetic Media





Under layer – Cr
Magnetic layer – CoPtCrB
Antiferromagnetic layer – Ru
Can be fabricated by decomposition
techniques such as sputtering
The Ruthenium layer is about 3 atom-thick
layer
Q&A