Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
1998-12-22
2001-07-10
Lorin, Francis J. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C360S125330, C427S131000, C428S680000, C428S681000
Reexamination Certificate
active
06258468
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to magnetic disk data storage systems, and more particularly to AMR read sensors for use in conjunction with 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.
2
). 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. 2
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 write element
26
is typically an inductive write element. A write gap
30
is formed between an intermediate layer
31
, which functions as a first pole, and a second pole
32
. Also included in write element
26
, is a conductive coil
33
that is positioned within a dielectric medium
34
. 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
.
The read element
28
includes a first shield
36
, the 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
24
is the magnetoresistive sensor. A magnetoresistive (MR) sensor is used to detect magnetic field signals by means of a changing resistance in the read sensor. When there is relative motion between the MR sensor and a magnetic medium (such as a disk surface), a magnetic field from the medium can cause a change in the direction of magnetization in the read sensor, thereby causing a corresponding change in resistance of the read element. The change in resistance can be detected to recover the recorded data on the magnetic medium.
One type of conventional MR sensor utilizes the anisotropic magnetoresistive (AMR) effect for such detection, including a soft adjacent layer (SAL)
42
, a spacer layer
44
, and MR stripe
46
, and a cap layer
48
, as shown in FIG.
3
. The resistance of the MR stripe
46
varies in proportion to the square of the cosine of the angle between the magnetization in the MR stripe and the direction of a sense current flowing through the MR stripe. Because the magnetization of the MR stripe
46
can be affected when it is exposed to an external field, a detected change in resistance can be used to detect an external field.
More particularly, when the read sensor magnetization is properly biased, for example by transverse biasing, the change in resistance &Dgr;R is proportional to small external fields. Such transverse bias can be provided by a bias layer, or soft adjacent layer (SAL)
42
, disposed near the MR stripe
46
. Materials such as cobalt (Co) based alloys and nickel-iron (NiFe) alloys, for example nickel-iron-rhodium (NiFeRh), can be used as the SAL
42
. However, to prevent exchange coupling and electrical shunting of the sensing current by the SAL
42
, a nonmagnetic, electrically insulating film, or spacer layer
44
, is interposed between the SAL
42
and the MR stripe
46
. The spacer layer
44
should, accordingly, have high resistivity, as well as substantially zero magnetic moment (i.e., be non-magnetic). Also, the better the thermal stability of the spacer layer
44
, the larger the maximum sensing current can be. In addition, a cap layer
48
can be included to protect the MR stripe
46
from oxidation that might degrade the sensor performance.
A performance parameter of such an MR sensor is the ratio of change in resistance, &Dgr;R, to the read sensor sheet resistance, R. This ratio, &Dgr;R/R, is sometimes referred to as the MR coefficient of the read sensor, with higher values indicating higher performance. Higher &Dgr;R/R can be achieved with thicker layers, however higher data density applications require thinner layers. As an alternative, &Dgr;R/R can be increased by heating the MR stripe
46
during fabrication, however, &Dgr;R/R is not increased if reactive layers are interfacially adjacent the MR stripe
46
. Further, such heating can damage other layers, such as the shields
31
and
36
. Therefore, instead of heating, &Dgr;R/R can be increased by forming the MR stripe on certain materials that are used as a seed layer.
Such a material that yields higher &Dgr;R/R when the MR stripe is formed on it, is tantalum (Ta). Also, because of its high resistivity, good thermal stability, and non-magnetic properties, tantalum (Ta) has been used for the spacer layer
44
, as shown in the read sensor
40
of FIG.
3
.
It has been proposed to use NiFeCr as a seed layer and spacer
52
between an MR stripe
46
and a SAL
42
in place of tantalum, as shown in the read sensor
50
of
FIG. 4
to achieve greater performance. However, it has been found that when a material such as NiFeRh is used for the SAL
42
, such a structure exhibits an undesirably low &Dgr;R/R. In particular, a NiFeRh/NiFeCr/MR read sensor exhibits a &Dgr;R/R on the order of less than 1.3%.
Thus, what is desired is an improved read sensor that results in a higher &Dgr;R/R, and therefore higher read performance, while minimizing sensing current shunting, and maximizing the allowable sensing current level.
SUMMARY OF THE INVENTION
The present invention provides a read sensor, and method for making the same, that exhibits a higher &Dgr;R/R and, therefore, increased read performance. This is accomplished by a read sensor structure that includes a NiFeCr seed layer and an electrically insulating spacer layer between an MR stripe and a soft adjacent layer formed of, for example, NiFeRh.
According to an embodiment of the present invention, a magnetic read element for use in magnetic data retrieval includes a magnetoresistive stripe and a seed layer formed of NiFeCr that is interfacially adjacent the magnetoresistive stripe. The read element also includes a spacer layer adjacent the seed layer, with the seed layer being disposed between the magnetoresistive stripe and the spacer layer. The spacer layer is formed of an electrically insulating material. In addition, a soft adjacent layer is included in the read element, adjacent the seed layer and formed of a low-coercivity, high-permeability magnetic material.
In another embodiment of the present invention, a magnetic device for reading data from a magnetic medium includes a first shield, a second shield disposed above the first shield, and a magnetic read sensor disposed between the first shield and the second shield. The magnetic read sensor includes a magnetoresistive stripe and a seed layer formed of NiFeCr that is interfacially adjacent the magnetoresistive stripe. The read element also includes a spacer layer interfacially adjacent the seed layer,
Basi Raman J.
Mahajan Sukesh
Mahvan Nader
Hayden Robert D.
Lorin Francis J.
Read-Rite Corporation
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