High speed, high areal density inductive writer

Details High speed, high areal density inductive writer High speed, high areal density inductive writer

2000-07-18

2003-09-09

Tupper, Robert S. (Department: 2652)

Dynamic magnetic information storage or retrieval

Head

Core

Reexamination Certificate

active

06618223

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to magnetic data recording and more specifically to a method for making a high data rate, high data density inductive writer.
BACKGROUND OF THE INVENTION
Magnetic disk drives are used to store and retrieve data for digital electronic apparatus 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 disk drive motor
14
, one or more magnetic disks
16
, supported for rotation by a drive spindle
18
of motor
14
, and an actuator
20
including at least one arm
22
, the actuator being attached to a pivot bearing
24
. Suspensions
26
are coupled to the ends of the arms
22
, and each suspension supports at its distal end a read/write head or transducer
28
. The head
28
(which will be described in greater detail with reference to
FIGS. 2A and 2B
) 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
28
causing it to lift slightly off of the surface of the magnetic disk
16
, or, as its 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
20
causes the transducer
28
to pivot in a short arc across a surface of the disk
16
. The pivotal position of the actuator
20
is controlled by a voice coil
30
which passes between a set of magnets (not shown) to be driven by magnetic forces caused by current flowing through the coil
30
.
FIG. 2A
shows the distal end of the head
28
, greatly enlarged so that a write element
32
incorporated into the head can be seen. The write element
32
includes a magnetic yoke
34
having an electrically conductive coil
36
passing therethrough.
The write element
32
can be better understood with reference to
FIG. 2B
, which shows the write element
32
and an integral read element
38
in cross section. The head
28
includes a substrate
40
above which the read element
38
and the write element
32
are disposed. A common edge of the read and write elements
38
,
32
, defines an air bearing surface ABS, in a plane
42
, which can be aligned to face the surface of the magnetic disk
16
(see FIGS.
1
A and
1
B). The read element
38
includes a first shield
44
, a second shield
46
, and a read sensor
48
that is located within a dielectric medium
50
between the first shield
44
and the second shield
46
. The most common type of read sensor
48
used in the read/write head
28
is the magnetoresistive (AMR or GMR) sensor, which is used to detect magnetic field signal changes in a magnetic medium by means of changes in the resistance of the read sensor imparted from the changing magnitude and direction of the magnetic field being sensed.
The write element
32
can be better understood with reference to
FIG. 2B
, which shows the write element
32
and an integral read element
38
in cross section The head
28
includes a substrate
40
above which the read element
38
and the write element
32
are disposed. A common edge of the read and write elements
38
,
32
, defines an air bearing surface ABS, in a plane
42
, which can be aligned to face the surface of the magnetic disk
16
(see FIGS.
1
A and
1
B). The read element
38
includes a first shield
44
, a second shield
46
, and a read sensor
48
that is located within a dielectric medium
50
between the first shield
44
and the second shield
46
. The most common type of read sensor
48
used in the read/write head
28
is the magnetoresistive (AMR or GMR) sensor, which is used to detect magnetic field signal changes in a magnetic medium by means of changes in the resistance of the read sensor imparted from the changing magnitude and direction of the magnetic field being sensed.
The write element
32
is typically an inductive write element that includes the second shield
46
(which functions as a first pole for the write element) and a second pole
52
disposed above the first pole
46
. Since the present invention focuses on the write element
32
, the second shield/first pole
46
will hereafter be referred to as the “first pole”. The first pole
46
and the second pole
52
contact one another at a backgap portion
54
, with these three elements collectively forming the yoke
34
. The combination of a first pole tip portion and a second pole tip portion near the ABS are sometimes referred to as the ABS end
56
of the write element
32
. Some write elements have included a pedestal
55
which can be used to help define track width and throat height A write gap
58
is formed between the first and second poles
46
and
52
in the area opposite the back gap portion
54
. The write gap
58
is filled with a non-magnetic, electrically insulating material that forms a write gap material layer
60
. This non-magnetic material can be either integral with or separate from a first insulation layer
62
that lies upon the first pole
46
and extends from the ABS end
56
to the backgap portion
54
. The conductive coil
36
, shown in cross section, passes through the yoke
34
, sitting upon the write gap material
60
. A second insulation layer
64
covers the coil and electrically insulates it from the second pole
52
.
An inductive write head such as that shown in
FIGS. 2A and 2B
operates by passing a writing current through the conductive coil
36
. Because of the magnetic properties of the yoke
28
, a magnetic flux is induced in the first and second poles
46
and
52
by write currents passed through the coil
36
. The write gap
58
allows the magnetic flux to fringe out from the yoke
34
(thus forming a fringing gap field) and to cross the magnetic recording medium that is placed near the ABS.
With reference to
FIG. 2C
, a critical parameter of a magnetic write element is the trackwidth of the write element which defines track density. For example, a narrower trackwidth can result in a higher magnetic recording density. The trackwidth is defined by the geometries in the ABS end
56
of the yoke. For example, the tack width can be defied by the width W
3
of the pedestal
55
or by the width W
1
of the second pole
52
, depending upon which is smaller. The widths W
3
and W
1
can be the same, such as when the second pole
52
is used to trim the pedestal
55
. Alternatively, in designs that have no pedestal at all it would be possible to define the trackwidth by the width W
2
of the first pole.
With reference to
FIG. 2B
, the fringing gap field of the write element can be further affected by the positioning of the zero throat level ZT. ZT is defined as the distance from the ABS to the first divergence between the first and second pole, and it can be defined by either the first or second pole
46
,
52
depending upon which has the shorter pole tip portion. Pedestal defined zero throat is defined by the back edge of the pedestal and is accomplished by moving the second insulation layer
64
back away from tee ABS. Alternatively, zero throat can be defined by the geometry of the second pole
52
, by allowing the second insulation layer
64
to extend over the top of the pedestal. In order to prevent flux leakage from the second pole
52
into the back portions of the first pole
46
, it is desirable to provide a zero throat level that is well defined with respect to the plane of the ABS. Furthermore, a pedestal defined zero throat is beneficially defined along a well defined plane that is parallel with the plane
42
of the ABS, whereas a zero throat defined by the second pole occurs along the sloped edge of the second insulation layer
64
. As will be appreciated upon a reading of the description of the invention, the present invention can be used with either pedestal defined zero throat or a second pole defined zero throat Thus, accurate definition of the trackwidth, and zero

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