Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2002-02-20
2004-11-23
Letscher, George J. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06822829
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to perpendicular magnetic recording heads, and more particularly, to a perpendicular magnetic recording head with a multilayered main write pole.
BACKGROUND OF THE INVENTION
Magnetic recording heads have utility for use in a magnetic disc drive storage system. Most magnetic recording heads used in such systems today are “longitudinal” magnetic recording heads. Longitudinal magnetic recording in its conventional form has been projected to suffer from superparamagnetic instabilities at densities above approximately 40 Gbit/in
2
. It is believed that reducing or changing the bit cell aspect ratio will extend this limit up to approximately 100 Gbit/in
2
. However, for recording densities above 100 Gbit/in
2
, different approaches will likely be necessary to overcome the limitations of longitudinal magnetic recording.
An alternative to longitudinal recording is “perpendicular” magnetic recording. Perpendicular magnetic recording is believed to have the capability of extending recording densities well beyond the limits of longitudinal magnetic recording. Perpendicular magnetic recording heads for use with a perpendicular magnetic storage medium may include a pair of magnetically coupled poles, including a main write pole having a relatively small bottom surface area and a flux return pole having a larger bottom surface area. A coil having a plurality of turns is located adjacent to the main write pole for inducing a magnetic field between that pole and a soft underlayer of the storage media. The soft underlayer is located below the hard magnetic recording layer of the storage media and enhances the amplitude of the field produced by the main pole. This, in turn, allows the use of storage media with higher coercive force, consequently, more stable bits can be stored in the media. In the recording process, an electrical current in the coil energizes the main pole, which produces a magnetic field. The image of this field is produced in the soft underlayer to enhance the field strength produced in the magnetic media. The flux density that diverges from the tip into the soft underlayer returns through the return flux pole. The return pole is located sufficiently far apart from the main write pole such that the material of the return pole does not affect the magnetic flux of the main write pole, which is directed vertically into the hard layer and the soft underlayer of the storage media.
A perpendicular magnetic recording system may utilize a main write pole having uniform magnetic properties, i.e. the main write pole is formed of a single material having a uniform magnetic moment. However, such a write pole can exhibit skew effects which can degrade adjacent tracks.
Perpendicular magnetic recording systems alternatively may utilize a main write pole having a “hybrid” design wherein, for example, a high saturation magnetic moment material is formed on top of a low saturation magnetic moment material. This type of design has been found effective in, for example, reducing skew effects during the writing process. However, it has been determined that for such a hybrid design, the low saturation magnetic moment material may induce a texture in the high saturation magnetic moment material which may impact the desired magnetic properties of the head design, such as an increase in the magnetic remanence.
Accordingly, there is identified a need for an improved perpendicular magnetic recording head that overcomes limitations, disadvantages, and/or shortcomings of known perpendicular magnetic recording heads. In addition, there is identified a need for an improved main write pole of a perpendicular magnetic recording head that overcomes limitations, disadvantages, and/or shortcomings of known main write poles.
SUMMARY OF THE INVENTION
Embodiments of the invention meet the identified needs, as well as other needs, as will be more fully understood following a review of the specification and drawings.
In accordance with an aspect of the invention, a main write pole for a perpendicular magnetic recording head comprises a first layer of material, a second layer of material, and an interlayer positioned between the first and second layers of material. The second layer of material has a saturation magnetic moment that is greater than a saturation magnetic moment of the first layer of material. The interlayer may include, for example, Al
2
O
3
, SiO
2
, Si
3
N
4
and/or any material which is amorphous or has little or no lattice matching with the magnetic layers. The first layer of material is magnetically exchanged coupled to the second layer of material through the interlayer. This results in formation of a main write pole having soft and uniaxial magnetic properties and a relatively low hard axis remanence.
In accordance with an additional aspect of the invention, a perpendicular magnetic recording head comprises a main write pole and a return pole magnetically coupled to the main write pole. The main write pole comprises a first layer of material, a second layer of material, and an interlayer positioned between the first layer of material and the second layer of material. The second layer of material has a greater saturation magnetic moment than the first layer of material.
In accordance with yet another aspect of the invention, a magnetic disc drive storage system comprises a housing, a perpendicular magnetic recording medium positioned in the housing, and a perpendicular magnetic recording head mounted in the housing adjacent the magnetic recording medium. The magnetic recording head includes a main write pole and a return pole magnetically coupled to the write pole. The main write pole includes a first layer of material, a second layer of material, and an interlayer positioned between the first layer of material and the second layer of material to magnetically exchange couple the first and second layers of material. The second layer of material has a greater saturation magnetic moment than the first layer of material.
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Klemmer Timothy J.
Minor Michael K.
Letscher George J.
Magee Christopher R.
Pietragallo Bosick & Gordon
Queen, II Benjamin T.
Seagate Technology LLC
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