Inductive write head for magnetic data storage media

Details Inductive write head for magnetic data storage media Inductive write head for magnetic data storage media

1998-11-23

2001-02-20

Pianalto, Bernard (Department: 1762)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Physical dimension specified

C360S119050, C360S122000, C360S123090, C428S692100, C428S697000, C428S900000

Reexamination Certificate

active

06190764

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates generally to magnetic disk data storage systems, and more particularly to inductive write heads for magnetic data storage media.
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 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
typically includes an inductive write element with a sensor read element (which will be described in greater detail with reference to FIG.
1
C). 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 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 write element
26
and a read element
28
. The edges of the write element
26
and read element
28
also define an air bearing surface ABS, in a plane
29
, which faces the surface of the magnetic disk
16
shown in
FIGS. 1A and 1B
.
The read element
28
includes a first shield
36
, an intermediate layer
31
, which functions as a second shield, and a read sensor
40
that is located between the first shield
36
and the second shield
31
and suspended within a dielectric layer
37
. The most common type of read sensor
40
used in the read/write head
30
is the magnetoresistive sensor which is used to detect magnetic field signals from a magnetic medium through changing resistance in the read sensor.
The write element
26
is typically an inductive write element. The intermediate layer
31
is shared between the read element
28
and the write element
26
, forming a first pole of the write element
26
. With a second pole
32
, the first pole
31
forms a yoke
38
. A write gap
30
is formed between the first pole
31
and the second pole
32
. Specifically, the write gap
30
is located adjacent to a portion of the first pole and second pole which is sometimes referred to as the yoke tip region
33
. The write gap
30
is filled with a non-magnetic material
39
. Also included in write element
26
, is a conductive coil
34
that is positioned within a dielectric medium
35
. The conductive coil
34
of
FIG. 1C
is formed of a first coil C
1
and a second coil C
2
. 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. 1D
, a view taken along line
1
D—
1
D of
FIG. 1C
(i.e., perpendicular to the plane
29
and therefore perpendicular to the air bearing surface ABS) further illustrates the structure of the write element
28
. As can be seen from this perspective, a pole width W of the first pole
31
and second pole
32
in the yoke tip region
30
are substantially equal. A parameter of any write element is its trackwidth which affects its performance. In the configuration of
FIG. 1D
, the trackwidth is defined by the pole width W.
FIGS. 1E and 1F
show two views of another prior art read/write head. The read element
28
of
FIG. 1E
is substantially the same as in the read/write head of FIG.
1
C. However, above and attached to the first pole
31
, is a first yoke pedestal Y
1
P in the yoke tip region
33
, abutting the ABS. In addition, a second yoke pedestal Y
2
P is disposed above and aligned with the first yoke pedestal Y
1
P. Further, the second yoke pedestal Y
2
P is adjacent to the second pole
32
. The write gap
30
is formed between the first and second yoke pedestals Y
1
P and Y
2
P.
The write element
26
of the prior art is shown in
FIG. 1F
as viewed along the line
1
F—
1
F of FIG.
1
E. Here it can be seen that the first and second yoke pedestals Y
1
P and Y
2
P have substantially equal pedestal widths Wp which are smaller than the pole width W of the first and second poles
31
and
32
in the yoke tip region
33
. In this configuration, the trackwidth of the write element
28
is defined by the width Wp.
An inductive write head such as those shown in
FIGS. 1C-1F
operates by inducing a magnetic flux in the first and second pole. This can be accomplished by passing a writing current through the conductive coil
34
. The write gap
30
allows the magnetic flux to fringe (thus forming a gap fringing field) and impinge upon a recording medium that is placed near the ABS. Thus, the strength of the gap field is a parameter of the write element performance. Other performance parameters include the non-linear transition shift (NLTS), which arises from interbit magnetostatic interactions that occur during the write process, and overwrite.
The amount of time that it takes the magnetic flux to be generated in the poles by the writing current (sometimes termed the “flux rise time”) is a critical parameter also, especially for high-speed write elements. In particular, the smaller the flux rise time, the faster the write element can record data on a magnetic media (i.e., a higher data rate). The extended flux rise time is an indicator of eddy current losses and head saturation in the write element. Thus, high data rate applications with large linear bit density and large track density can be accommodated by a writer having a large gap field and low eddy current loss.
It has been found that the yoke length YL of the second pole
32
influences the flux rise time, as is shown by the curves in the graph of FIG.
2
A. The corresponding impact of yoke length on data rate can be seen with reference to the curves of FIG.
2
B. As can be seen in
FIGS. 2A and 2B
, the flux rise time, and therefore data rate, of a typical second pole of 35% FeNi can be improved with lamination. However, such lamination can increase the fabrication process complexity, for example increasing cycle time as well as cost of fabrication.
It has also been found that materials with higher electrical resistivity &rgr; exhibit smaller flux rise times, which indicates that using such materials can reduce eddy current loss in a write clement. Other material properties desired in a write material include high saturation magnetic flux density Bs, low saturation magnetostriction &lgr;s, and good corrosion resistance.
Materials that have been used to form the poles in write elements include NiFe, CoFe, CoNiFe, CoZrTa, and FeN. The saturation magnetic flux density, saturation magnetostriction &lgr;s, and corrosion resistance of these materials are listed in the table of FIG.
3
. Higher Fe concentration in NiFe alloy does enhance its saturation magnetic flux density Bs, but the magnetostriction &lgr;s of the resultant NiFe alloy increases rapidly. For example, Ni
45
Fe
55
, has Bs and &lgr;s values of 15.5 kGauss and 20×10
−6
, respectively. In addition, the NiFe alloy family has low electrical resistivity which can inhibit high speed applications because of high eddy current losses. CoFe and CoNiFe also suffer from low electrical resistivity. Also, while Fe based nitride films and their derivatives can have high Bs values when the nitrogenized films are in crystallized bcc phase, they require film lamination to overcome their low electrical resistivity for high data rate applications. As an additional option, CoZrTa, having a relatively large electrical resistivity, can be used. However, CoZrTa exhibits poor corrosi

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