Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-08-20
2004-01-20
Cao, Allen (Department: 2152)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06680829
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the field of electronic data storage and retrieval systems. In particular, the present invention relates to a novel configuration of a shielded magnetoresistive element of a transducing head.
In an electronic data storage and retrieval system, a transducing head typically includes a reader portion having a magnetoresistive (MR) sensor for retrieving magnetically-encoded information stored on a magnetic disc. MR sensors may be anisotropic magnetoresistive (AMR) sensors or giant magnetoresistive (GMR) sensors. AMR sensors generally have a single MR layer formed of a ferromagnetic material. GMR sensors generally have multiple layers of ferromagnetic material.
When an MR sensor is placed in close proximity to a rotating magnetized storage disc, the MR layer is exposed to magnetic bit fields previously written on the disc surface. Exposing the MR element to the magnetic bit fields in this way, affects the magnetization vector of the MR element. When a current is passed through the MR element, changes in resistance are detected as voltage changes. The change in resistance of the MR layer is due to the changing magnetization vector of the MR element. External circuitry then converts the voltage information into an appropriate format and manipulates that information into a series of binary ones and zeros that represent the recorded bits on the storage disc.
The information that is being read by the MR element is initially stored on the magnetic discs along concentric circular tracks or microtracks. A bit is the smallest unit of data that is stored on each microtrack. Obviously, only a finite amount of bits can be stored along a microtrack, and it is desirable to maximize that number. The number of bits written along a distance of one inch on one of those microtracks is called the linear bit density. It is also desirable to maximize the number of microtracks that are on a disc. The number of microtracks per inch along a radius of the disc is called the track density. The areal density is the product of the linear bit density and the track density. One way to accomplish the goal of increasing the total amount of information stored on a magnetic disc is to increase the areal density, that is, increase the bits stored in a microtrack, increase the amount of microtracks on a disc, or increase both.
As areal density increases, however, it becomes more and more difficult to read magnetically stored bits without also reading adjacent stored bits. As an ever-increasing amount of information is stored on a magnetized storage disc, it becomes more difficult for MR sensors to separately read the stored information without also reading noise from adjacent stored information.
This problem may be alleviated somewhat in MR sensors by placing soft magnetic material above and below the MR element to shield the element from the influence of bit fields of adjacent bits in a particular microtrack. During a read operation, these top and bottom shields typically insure that the MR sensor reads only the information stored directly beneath it on a specific microtrack of the magnetic medium or disc by absorbing any stray magnetic fields emanating from down track.
Top and bottom shields typically shield well as linear bit density increases, but they do not adequately shield stray magnetic fields from magnetically stored bits in adjacent microtracks to the microtrack being read at a particular time by the MR sensor when track density increases. As the track density increases, that is, as adjacent microtracks become closer and closer together, it becomes more imperative that a MR sensor is reading from only a single microtrack at any particular time and not from adjacent microtracks. As track pitch increases, that is, as spacing between adjacent microtracks become smaller, the reading error will increase. A MR sensor that accurately reads high track pitch media is a necessary improvement over the art of record.
BRIEF SUMMARY OF THE INVENTION
The present invention introduces a novel configuration of a shielded MR sensor for a read element of a magnetic head. The MR sensor includes an MR element that further has a top shield, a bottom shield, and first and second side shields. The first and second side shields decrease the response signal in the MR sensor to due to adjacent microtracks that are not intended to be read at a particular point in time. This allows accurate reading by MR sensor even where track density is relatively high.
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Chen Jian
Chen Lujun
Fernandez-de-Castro Juan Jose
Giusti James
Mao Sining
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