Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1999-02-11
2001-01-23
Klimowicz, William (Department: 2754)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S123090, C360S125330, C360S119050
Reexamination Certificate
active
06178070
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to magnetic disk data storage systems, and more particularly to magnetic write heads 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 systems
10
of the prior art includes a sealed enclosure
12
, a disk drive motor
14
, a magnetic disk
16
, supported for rotation by a drive spindle S
1
of motor
14
, 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
(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. Various magnetic “tracks” of information can be written to and/or read from the magnetic disk
16
as the actuator
18
causes the transducer
24
to pivot in a short 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. 1C
depicts a magnetic read/write head
24
including a read element
26
and a write element
28
. The edges of the read element
26
and write element
28
also define an air bearing surface ABS, in a plane
29
, which faces the surface of the magnetic disk
16
.
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 (MR 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
abutting the ABS. In addition, a second pole pedestal
44
is attached to the second pole
38
at a second pole tip portion
45
and 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 region
46
. A write gap
36
is formed between the first and second pole pedestals
42
and
44
in the yoke tip region
46
. The write gap
36
is filled with 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 yoke
38
and extends from the yoke tip region
46
to the backgap portion
40
. Also included in write element
28
is a conductive coil
48
, formed of multiple winds, that is positioned within a dielectric medium
50
that lies above the first insulation layer
47
. The configuration of the conductive coil
48
can be better understood with reference to a plan view of the read/write head
24
shown in
FIG. 1D
taken along line
1
D—
1
D of FIG.
1
C. As is well known to those skilled in the art, these elements operate to magnetically write data on a magnetic medium such as a magnetic disk
16
.
In
FIG. 1E
, a view taken along line
1
E—
1
E of
FIG. 1C
(i.e., perpendicular to the plane
29
) further illustrates the structure of the read/write head
24
at the ABS. As can be seen from this view and in the view of
FIG. 1C
, 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 poles
32
and
38
in the yoke tip region
46
. A critical parameter of a magnetic write element is a trackwidth defined by the geometries at the ABS. In this configuration, the trackwidth of the write element
28
is substantially equal to the width Wp. An inductive write head such as that shown in FIGS.
1
C-
1
E operates by passing a writing current through the conductive coil
48
.
Because of the magnetic properties of the yoke
41
, a magnetic flux is induced in the first and second poles
32
and
38
by write currents in coil
48
. The more winds between the first and second poles
42
and
44
, the larger the magnetic flux that can be induced. The write gap
36
allows the magnetic flux to fringe out from the yoke
41
(thus forming a fringing gap field) and to cross a magnetic recording medium that is placed near the ABS. In this way, the write element performance is directly driven by the strength of this gap field. Thus, with a particular current, more winds results in a higher write element performance due to higher magnetic flux.
More winds in the conductive coil
48
could be included between the first and second poles by increasing the yoke length YL. Unfortunately, the recording speed is inversely related to the yoke length YL. In particular, as shown in
FIG. 1F
, increasing yoke length increases flux rise time, i.e., the time that it takes the magnetic flux to be generated in the poles by the writing current. The higher the flux rise time, the slower the write element can record data on a magnetic media (i.e., a lower data rate). As shown by the graph of
FIG. 1F
, with increasing yoke length YL, the flux rise time increases thereby decreasing recording speed of the write element.
Again referring to
FIG. 1C
, another way that more winds could be included in the write element could be forming additional winds in one or more additional conductive coils (not shown) above the conductive coil
48
. However, this increases the stack height SH of the write element (i.e., causes a higher topography). Unfortunately, the reliability of the write element is inversely related to the stack height SH. For example, with higher topography the formation of the second pole, such as by sputtering or plating, can lead to undesirable material properties.
Another problem which increases with increasing stack height is cracking of the write element due to thermal expansion and thermal coefficient mismatch. For example, when adjacent insulation layers are formed of different materials that have different thermal coefficients, during heating the two materials may expand at different rates. When the stack height increases, the attendant geometries result in increasing likelihood of separation between the second pole
38
and the second pole pedestal
44
. Regardless of the mechanism of reduced reliability, this results in undesirable lower production yield.
Alternatively, a larger writing current can be used with fewer winds to achieve the same performance. Unfortunately, however, higher current can cause higher heat levels, thus increasing problems associated with higher temperature operation. Thus, in design of write elements, tradeoffs are made between the number of winds, yoke length, and write current strength to achieve desired writing performance.
Accordingly, what is desired is an easily fabricated, reliable write element that exhibits a faster flux rise time while minimizing heat problems due to the writing current. In particular, a write element that accommodates a larger number of conductive coil winds for a given yoke length and stack height is needed.
SUMMARY OF THE INVENTION
The present invention provides a magnetic write head and method for making the same that provides high writing perform
Hong Liubo
Shi Zhupei
Hickman Coleman & Hughes LLP
Klimowicz William
Read-Rite Corporation
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