Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-11-17
2003-02-18
Heinz, A. J. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06522508
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to read head portions of magnetic heads for disk drives, and more particularly to magnetic keeper elements for such read heads to balance magnetic fields at the free magnetic layer within such heads.
2. Description of the Prior Art
The typical prior art read head elements of a magnetic head include a plurality of thin film layers that are deposited and fabricated to produce a GMR read head, as is known to those skilled in the art. A significant functional aspect of such heads is the orientation of the magnetic field within the free magnetic layer, and it is important for the proper operation of the read head that there be a minimum (near zero) biasing magnetic field at the free layer. It has been recognized that the various magnetic layers of the prior art read head, as well as the flow of electrical current through the read head layers, create unwanted biasing magnetic fields at the free layer. An effort to cure this problem has been the addition of a magnetic keeper layer, which produces a counterbalancing magnetic field at the free magnetic layer to balance out the overall magnetic fields at the free magnetic layer.
In prior art magnetic keeper layer designs, electrical current that flows through the read head also flows through the keeper layer. This creates an unwanted shunting of electrical current that would otherwise flow through the read head layers, thus degrading the performance of the read head. Additionally, because the keeper layer is not electrically isolated from the other read head layers, the magnetic initialization of the hard bias elements of the read head also results in the magnetic setting of the keeper layer, and it is difficult to separately set or reset the magnetization of the keeper layer. The present invention solves these problems with a read head structure in which the keeper layer is electrically insulated from the remaining read head layers. Thus the magnetization of the keeper layer of the present invention can be separately set or reset as desired.
SUMMARY OF THE INVENTION
The magnetic head of the present invention includes a GMR layer structure that includes a magnetic keeper layer. An electrical insulation layer is fabricated between the keeper layer and the remaining layers of the GMR head, such that electrical current which passes through the read head layers does not pass through the keeper layer. In the preferred embodiment, the keeper layer is composed of a ferromagnetic material, such as NiFe, and the insulation layer is composed of an antiferromagnetic material such as NiO. Once the magnetization of the keeper layer is set, it becomes exchange coupled with the antiferromagnetic layer to pin the keeper layer magnetization. Because the keeper layer is electrically insulated it does not shunt electrical current of the read head, thus the thickness of the keeper layer is unconstrained by the electrical shunting problems of the prior art. Additionally, because the keeper layer is electrically insulated from the read head components, its magnetization can be separately set, or reset utilizing current pulses that pass only through it. In a first preferred embodiment, the keeper layer is fabricated prior to the fabrication of the remaining GMR read head layers, and in a second preferred embodiment, the keeper layer is fabricated following the fabrication of the GMR read head layers.
It is an advantage of the magnetic head of the present invention that an electrically isolated keeper layer is provided.
It is another advantage of the magnetic head of the present invention that an electrically isolated keeper layer is provided, such that the magnetization of the keeper layer can be separately set or reset.
It is a further advantage of the magnetic head of the present invention that an electrically isolated keeper layer is provided, such that the, thickness of the keeper layer is relatively unconstrained.
It is yet another advantage of the magnetic head of the present invention that the external magnetic fields at the free layer of the read head can be more effectively balanced.
It is an advantage of the hard disk drive of the present invention that it includes a magnetic head having an electrically isolated keeper layer.
It is another advantage of the hard disk drive of the present invention that it includes a magnetic head having an electrically isolated keeper layer, such that the magnetization of the keeper layer can be separately set or reset.
It is a further advantage of the hard disk drive of the present invention that it includes a magnetic head having an electrically isolated keeper layer, such that the thickness of the keeper layer is relatively unconstrained.
It is yet another advantage of the hard disk drive of the present invention that it includes a magnetic head wherein the external magnetic fields at the free layer of the read head can be more effectively balanced.
These and other features and advantages of the present invention will no doubt become apparent to those skilled in the art upon reading the following detailed description which makes reference to the several figures of the drawings.
REFERENCES:
patent: 5508867 (1996-04-01), Cain et al.
patent: 6178072 (2001-01-01), Gill
Guillot Robert O.
Heinz A. J.
Intellectual Property Law Offices
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