Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
1999-04-08
2001-08-28
Cao, Allen T. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06282056
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to magnetic disk data storage systems, and more particularly to a magnetic write head design and methods for making same.
Magnetic disk drives are used to store and retrieve data for digital electronic apparatuses such as computers. In
FIGS. 1A and 1B
, a magnetic disk data storage system
10
of the prior art includes a sealed enclosure
12
, a medium motor
14
, a magnetic medium or disk
16
, supported for rotation by a drive spindle S
1
of the medium motor
14
, an actuator
18
and an arm
20
attached to an actuator spindle S
2
of actuator
18
. A read/write head support system consists of a suspension
22
coupled at one end to the arm
20
, and at its other end to a read/write head or transducer
24
.
The transducer
24
(which will be described in greater detail with reference to
FIG. 1C
) typically includes an inductive write element with a sensor read element. As the motor
14
rotates the magnetic disk
16
, as indicated by the arrow R, an air bearing is formed under the transducer
24
causing it to lift slightly off of the surface of the magnetic disk
16
, or, as it is termed in the art, to “fly” above the magnetic disk
16
. Alternatively, some transducers, known as “contact heads,” ride on the disk surface. Discrete units of magnetic data, known as “bits,” are typically arranged sequentially in multiple concentric rings, or “tracks,” on the surface of the magnetic medium. Data can be written to and/or read from essentially any portion of the magnetic disk
16
as the actuator
18
causes the transducer
24
to pivot in a short arc, as indicated by the arrows P, over the surface of the spinning magnetic disk
16
. The design and manufacture of magnetic disk data storage systems is well known to those skilled in the art.
FIG. 1C
depicts a magnetic read/write head
24
including a read element
26
and a write element
28
. A common surface known as the air bearing surface ABS in the plane
29
, is shared by the read element
26
and write element
28
. The magnetically active components of both the read element
26
and the write element
28
terminate at the ABS, which faces the surface of the magnetic disk
16
(see FIG.
1
A). This configuration minimizes the distance between the magnetic medium
16
and the magnetically active components of the magnetic read/write head
24
for optimal reading and writing performance.
The read element
26
includes a first shield
30
, an intermediate layer
32
, which functions as a second shield, and a read sensor
34
that is located between the first shield
30
and the second shield
32
. The most common type of read sensor
34
used in the read/write head
24
is the magnetoresistive (AMR or GMR) sensor which is used to detect magnetic field signals from a magnetic medium through changing resistance in the read sensor.
The write element
28
is typically an inductive write element. The write element
28
includes the intermediate layer
32
, which functions as a first pole, and a second pole
38
disposed above the first pole
32
. The first pole
32
and the second pole
38
are attached to each other by a backgap portion
40
, with these three elements collectively forming a yoke
41
. Above and attached to the first pole
32
at a first pole tip portion
43
, is a first pole pedestal
42
exposed along the ABS. In addition, a second pole pedestal
44
is attached to the second pole
38
at a second pole tip portion
45
and is aligned with the first pole pedestal
42
. This portion of the first and second poles
42
and
44
near the ABS is sometimes referred to as the yoke tip portion
46
.
A write gap
36
is formed between the first and second pole pedestals
42
and
44
in the yoke tip portion
46
. The write gap
36
is made of a non-magnetic material. This non-magnetic material can be either integral with (as is shown here) or separate from a first insulation layer
47
that lies below the second pole
38
and extends from the yoke tip portion
46
to the backgap portion
40
.
Also included in write element
28
is a conductive coil
48
, formed of multiple winds
49
. Typically, the winds
49
of the conductive coil
48
spiral around the portion of the second pole near the backgap portion
40
in a plane that is substantially perpendicular to the viewing plane of FIG.
1
C. Some designs in the prior art employ several substantially parallel conductive coils arranged in a stack, rather than the single conductive coil
48
illustrated. For ease of viewing, complete winds are not shown.
The conductive coil
48
is positioned within a non-magnetic and electrically insulating medium
50
that lies above the first insulation layer
47
. As is well known to those skilled in the art, current passed through the conductive coil
48
magnetizes the yoke
41
and creates a magnetic field across the write gap
36
between the first and second pole pedestals
42
and
44
. The magnetic field across the write gap
36
can induce a reorientation of magnetic domains in a nearby magnetic medium such as a magnetic disk
16
(see FIG.
1
A). Changing the magnetic field across the write gap
36
as the write gap
36
is moved relative to, and in close proximity with, a magnetic medium
16
can induce corresponding variations in the orientations of magnetic domains within the magnetic medium along the write element path of travel. The smallest region on the surface of the magnetic disk
16
that may be induced to have coherently oriented magnetic domains typically constitutes a single bit. By this process bits may be sequentially written along a track on the surface of the magnetic disk
16
.
In
FIG. 1D
, a view taken along line
1
D—
1
D of
FIG. 1C
further illustrates the structure of the read/write head
24
. As can be seen from this view, the first and second pole pedestals
42
and
44
have substantially equal widths of Wp which are smaller than the width W of the first and second pole tip portions
32
and
38
in the yoke tip portion
46
.
Of critical importance to the disk drive industry is the total quantity of information that can be written within a unit area on the surface of a magnetic disk
16
. This quantity is sometimes referred to as the areal density and is typically expressed in terms of bits per square inch. The number of bits per square inch is a function of two primary factors: how many bits can be written within a unit length of a track, known as the linear density and expressed as bits per inch; and how many tracks can be placed within a unit area, known as the track density and expressed as tracks per inch. The linear density and the track density are each functions of several variables.
The linear density is a function of the length of the bits and the spacing between them, and is maximized by making the bits smaller and placed closer together. To maintain data integrity, though, bits cannot overlap. One of the problems in the prior art that limits the ability to place bits closer together is a phenomenon sometimes referred to as the second pulse effect. The second pulse effect is a problem whereby the process of writing a bit on a track actually produces two bits, a first intended bit closely followed in the track by a second unintended bit. Ordinarily, the second unintended bit is smaller than the first bit and the two bits may be distinguished on this basis. However, the very presence of the second unintended bit close behind the first intended bit precludes writing another intended bit in the unintended bit's place. Thus, these spurious unintended bits created by the second pulse effect can limit how closely legitimate intended bits may be written in a track.
The track density is a function of the trackwidth, which is also the width of the individual bits written within the track, and the spacing between the tracks. Maximization of track density is achieved by making bits narrower and by reducing the spacing between tracks. The width of a written bit is essentially a function of the dimensions of the write element at the ABS
Crue, Jr. Bill W.
Feng Aiguo
Shi Zhupei
Cao Allen T.
Hayden Robert D.
Read-Rite Corporation
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