Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2002-03-14
2004-09-28
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S324200
Reexamination Certificate
active
06798624
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention is related to recording heads for magnetic recording devices such as a disc drive, and more particularly to an apparatus for sensing write field characteristics for perpendicular and longitudinal recording leads.
2. Description of the Prior Art
The fast-paced evolution to smaller physical features in recording heads is surpassing the capability of traditional wafer metrology, such as tools that measure critical dimension or overlay accuracy, to accurately assess the quality of write heads. Moreover, manufacturers are moving to more performance-based metrics in the evaluation and development of write head technology.
SUMMARY OF INVENTION
It is therefore an aspect of the present invention to provide a way to measure such performance. The above and other objects, features and advantages of the present invention are attained by using a magnetization sensor to measure the write field characteristics of the write head of a disc drive. The sensor comprises a hard magnetic layer and a soft magnetic layer having a non-magnetic layer therebetween. Electrical leads are provided for applying an electrical current bias to the sensor and for obtaining sensor readings.
In a method of manufacturing a write field sensor, a soft underlayer is provided and has a hard magnetic material deposited on a portion thereof. A non-magnetic material is deposited on the hard magnetic material and a soft magnetic material is deposited on the non-magnetic material. Means are also provided for applying a biasing current to the sensor.
The sensor may be fabricated with the write head during the write head build process. Longitudinal write heads are usually built such that the wafer surface is planarized at the write gap. Therefore, the fabrication of the sensor can be performed during this stage of the build process before the rest of the write head build is completed. In addition to the building of the sensor, the write head build process is modified so that an “air bearing surface” plane is defined on the wafer (i.e. the throat height is defined through wafer lithography rather than lapping).
The present invention therefore provides a method to characterize the write field from both perpendicular and longitudinal recording heads by using an on-wafer magnetoresistive sensor utilizing a hard layer with strong perpendicular anisotropy, which has many advantages over prior art methods and devices.
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Covington Mark W.
Crawford Thomas M.
Buchanan & Ingersoll PC
Carleton Dennis M.
Evans Jefferson
Seagate Technology LLC
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