Compact MR write structure

Details Compact MR write structure Compact MR write structure

1999-06-18

2002-10-15

Vo, Peter (Department: 3729)

Dynamic magnetic information storage or retrieval

Head

Core

C360S122000

Reexamination Certificate

active

06466402

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates generally to magnetic data storage systems, more particularly to magnetoresistive read/write heads, and most particularly to an especially compact write structure.
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
includes a sealed enclosure
12
, a disk drive motor
14
, and a magnetic disk, or media,
16
supported for rotation by a drive spindle S
1
of motor
14
. Also included are an actuator
18
and an arm
20
attached to an actuator spindle S
2
of actuator
18
. A suspension
22
is coupled at one end to the arm
20
, and at its other end to a read/write head or transducer
24
. The transducer
24
typically includes an inductive write element with a sensor read element (both of which will be described in greater detail with reference to FIG.
2
A). 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 sometimes termed in the art, to “fly” above the magnetic disk
16
. With the arm
20
held stationary, data bits can be read along a circumferential “track” as the magnetic disk
16
rotates. Further, information from concentric tracks can be read from the magnetic disk
16
as the actuator
18
causes the transducer
24
to pivot in an arc as indicated by the arrows P. The design and manufacture of magnetic disk data storage systems is well known to those skilled in the art.
FIG. 2A
depicts a magnetic read/write head
24
including a read element
26
and a write element
28
. Edges of the read element
26
and write element
28
also define an air bearing surface ABS, in a plane
29
, which can be aligned to face the surface of the magnetic disk
16
(see FIGS.
1
A and
1
B). 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 within a dielectric medium
35
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 which includes the intermediate layer
32
, which functions as a first pole, and a second pole
38
. A first pole pedestal
42
may be connected to a first pole tip portion
43
of the first pole
32
, and a second pole pedestal
44
may be connected to the second pole tip portion
45
of the second pole
38
. The first pole
32
and the second pole
38
are attached to each other by a backgap
40
located distal to their respective pole tip portions,
43
and
45
. The first pole
32
, the second pole
38
, and the backgap
40
collectively form a yoke
41
together with the first pole pedestal
42
and the second pole pedestal
44
, if present. The area around the first pole tip portion
43
and the second pole tip portion
45
near the ABS is sometimes referred to as the yoke tip region
46
. A write gap
36
is formed between the first pole pedestal
42
and the second pole pedestal
44
in the yoke tip region
46
. The write gap
36
is formed of a non-magnetic electrically insulating material. This non-magnetic material can be either integral with (as is shown here) or separate from a first insulation layer
47
that lies between the first pole
32
and the second pole
38
, and extends from the yoke tip region
46
to the backgap
40
.
Also included in write element
28
is a conductive coil layer
48
, formed of multiple winds
49
. The conductive coil layer
48
is positioned within a coil insulation layer
50
that lies above the first insulation layer
47
. The first insulation layer
47
thereby electrically insulates the coil layer
48
from the first pole
32
, while the coil insulation layer
50
electrically insulates the winds
49
from each other and from the second pole
38
. In some prior art fabrication methods, the formation of the coil insulation layer includes a thermal curing of an electrically insulating material, such as photoresistive “photoresist” material.
FIG. 2B
shows a plan view of the read/write head
24
taken along line
2
B—
2
B of FIG.
2
A. This view better illustrates how the coil layer
48
of write element
28
is configured as a spiral with each wind
49
passing around the backgap
40
and beneath the second pole
38
in the region between the backgap
40
and the second pole tip region
45
. Because of the magnetic properties of the yoke
41
, when a write current is passed through coil layer
48
a magnetic flux is induced in the first and second poles
32
and
38
. The write gap
36
, being non-magnetic, allows the magnetic flux to fringe out from the yoke
41
, thus forming a fringing gap field. Data may be written to the magnetic disk
16
by placing the ABS of read/write head
24
proximate to the magnetic disk
16
such that the fringing gap field crosses the surface of the magnetic disk
16
. Moving the surface of the magnetic disk
16
through the fringing gap field causes a reorientation of the magnetic domains on the surface of the magnetic disk
16
. As the magnetic disk
16
is moved relative to the write element
28
, the write current in coil layer
48
is varied to change the strength of the fringing gap field, thereby encoding data on the surface of the magnetic disk
16
with a corresponding variation of oriented magnetic domains.
Returning to
FIG. 2A
, a number of parameters that influence the performance of the write element
28
are also shown. The first of these parameters is the yoke length YL, sometimes defined as the distance from the backgap
40
to the first pole pedestal
42
. A shorter yoke length YL favors higher data recording rates as it tends to reduce the flux rise time. The flux rise time is a measure of the time lag between the moment a current passed through coil layer
48
reaches its maximum value and the moment the fringing flux field between the first pole
32
and the second pole
38
reaches its maximum. Ideally, the response would be instantaneous, but various factors such as the physical dimensions and the magnetic properties of the yoke
41
cause the flux rise time to increase. A shorter flux rise time is desirable both to increase the rate with which data may be written to a magnetic disk
16
, and also to decrease the length of, and the spacing between, data bits on the magnetic disk
16
. Shorter data bits more closely spaced together is desirable for increasing the total storage capacity of the magnetic disk
16
.
Write elements according to the prior art are manufactured through common photolithography techniques well known in the art involving repeated cycles of masking with “photoresist,” depositing layers of various materials, followed by stripping away remaining photoresist. Each cycle through this process typically fabricates one element of the final structure. Consequently, tolerance for mask misalignment must be accounted for in the designs for these devices. In particular, prior art write elements leave a separation of at least 4 microns between pole pedestals
42
and
44
and the coil layer
48
. A similar gap of at least 4 microns is found between the backgap
40
and the coil layer
48
. These separations add extra length to the yoke length YL that increases the flux rise time and hinders write performance.
Another parameter of the write element
28
is the stack height SH, sometimes defined as the distance between the top surface of the first pole
32
and the top of the second pole
38
, as shown in FIG.
2
A. The stack height SH is influenced by the apex angle &agr;, which characterizes the angle of the slope region of the second pole
38
near the yoke tip portion
46
measured relative to a horizontal reference su

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