Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-01-19
2003-03-25
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06538847
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a high-density recording magnetic head, and more particularly to a magnetic core construction for inductive magnetic heads used for recording information on a high-density recording magnetic disk.
2. Description of the Related Art
A most commonly used magnetic head for magnetic disk drives is a combination of inductive magnetic and magnetoresistive heads in which the inductive magnetic head records information on a magnetic recording medium in a magnetic disk drive, while the magnetoresistive head reads the information recorded on the magnetic recording medium. As the magnetoresistive head, laminated layers of a magnetoresistive element, such as Ni—Fe, and a conductive SAL (soft adjacent layer), with a layer of material having a relatively large electrical resistance, such as Ta interposed between them are used. The magnetoresistive element is longitudinally magnetized by applying a static magnetic field to the three-layer laminate in the longitudinal direction. When a sensing current is caused to flow in the three layers in the longitudinal direction, a magnetic field is produced around the SAL by the current shunted in the SAL. The magnetic field thus produced changes the magnetization angle in the magnetoresistive element to approximately 45 degrees with respect to the longitudinal direction. When this magnetoresistive element is disposed facing the magnetic recording medium, the magnetization angle of the magnetoresistive element is changed by the magnetic information in the magnetic recording medium. Since the electrical resistance of the magnetoresistive element layer to the sensing current changes in accordance with the change in the angle, the magnetic information in the magnetic recording medium can be read.
There is a spin-bulb type in the magnetoresistive head. In the spin-bulb magnetoresistive head, two, ferromagnetic thin films are laminated with a non-magnetic thin film interposed between them, and one of the ferromagnetic thin films is disposed adjoining an anti-ferromagnetic thin film, with the magnetization direction in the ferromagnetic thin film being pinned, and the magnetization angle in the other ferromagnetic thin film being allowed to be in a free state. When this magnetoresistive head is disposed facing the magnetic recording medium, the magnetization angle in the ferromagnetic thin film that is kept in a free state changes in accordance with the magnetic information stored in the magnetic recording medium. This magnetization direction relatively changes with the fixed magnetization in the other ferromagnetic thin film. As the relative magnetization direction in the ferromagnetic thin films on both sides of the non-magnetic thin film changes, the electrical resistance to the sensing current flowing in the non-magnetic thin film also changes, and as a result, the magnetic information stored in the magnetic recording medium can be read.
Typical magnetoresistive heads commonly used for reading information in this manner include a type using the magnetoresistive effective element, and that using the spin bulb, but heads of constructions other than these are also being used to read magnetic information from the magnetic recording medium.
As a magnetic head used with magnetic recording media for magnetic disk drives, a composite magnetic head comprising a laminate of a magnetoresistive head and an inductive magnetic head, as described above, is formed on a head slider. On a head slider made of nonmagnetic insulating ceramic material provided is a magnetoresistive head between upper and lower shields with an insulating thin film interposed between them. The upper shield also serves as a lower magnetic core for the inductive magnetic head, on which an upper magnetic core is provided; the tips of the lower and upper magnetic cores forming magnetic poles of the inductive magnetic head. The magnetic poles of the inductive magnetic head and the magnetoresistive element are provided facing the air bearing surface, that is, a surface facing the magnetic recording medium of the head slider. A magnetic path is formed by the upper and lower magnetic cores of the inductive magnetic head, and an induction (or exciting) coil is wound in such a manner as to surround the magnetic path.
The lower magnetic core of the inductive magnetic head has an almost flat construction, and a non-magnetic gap layer comprising an insulating thin film, such as alumina, is formed over almost the entire surface of the lower magnetic core. On the non-magnetic gap layer formed are an insulating resin layer, a coil and another insulating resin layer enclosing the coil, on which an upper magnetic core is formed. The upper magnetic core is provided directly on the non-magnetic gap layer in an area which serves as a magnetic pole, directly on the lower magnetic core in an area where the upper magnetic core is connected to the lower magnetic core, and on a laminate of the coil and the insulating resin layer in a back area between the magnetic poles and the connecting part. When a photoresist mask is formed to provide an upper magnetic core in an area where there is a level difference as high as 6 to 20 &mgr;m, as found in the back area between the magnetic poles and the connecting part, patterning errors could unwantedly increase to an extent not suitable for forming narrow-track magnetic poles for high-density recording.
To cope with this, a construction has been proposed where the upper magnetic core is formed by dividing it into a front portion near the magnetic poles and a rear portion near the back area; the front portion formed directly on the non-magnetic gap layer and the rear portion formed extending from an upper surface of the front portion and over the coil and a coil insulating layer covering the coil. In this construction, the upper magnetic core front portion usually has a reduced width almost equal to a track width at the magnetic poles, that is, on a surface facing the recording medium, or a medium-facing surface; the width becoming gradually wider into a sectoral shape as the upper magnetic core goes far from the medium-facing surface. To obtain an accurate gap depth, an apex is provided on a surface facing the gap near the magnetic pole tips, and an area of the gap-facing surface of the upper magnetic core front portion from the medium-facing surface to the apex constitutes a magnetic gap with the lower magnetic core on the non-magnetic gap layer; an area at the rear of the apex being formed on another insulating layer overlapping the non-magnetic gap layer. With this construction, leakage flux between the upper and lower magnetic cores is reduced in the area at the rear of the apex on the upper magnetic core front portion.
Although the upper magnetic core rear portion is provided with a tip thereof connected to the upper magnetic core front portion, the tip of the upper magnetic core rear portion is formed at an area as remote as possible from the medium-facing surface to prevent leakage flux from the tip of the upper magnetic core rear portion to a recording medium, thereby preventing incidental erase.
In the manufacture of magnetic heads, a magnetic gap depth is provided by polishing the air-bearing surface of the composite magnetic head laminated on the head slider. With the entire upper magnetic core front portion formed into a sectoral shape, as described above, the track width tends to change depending on the polishing depth in polishing the air-bearing surface. With the front portion formed into a sectoral shape, a slight deviation of the polishing depth from a predetermined value could result in a change in the track width. To cope with the difficulty in controlling the track width to a desired value, a method of controlling the track width regardless of the machining depth of the air-bearing surface has been practiced by using a rectangular upper magnetic core front portion.
As described above, an apex is provided near the surface facing the recording medium on the upper mag
Fujii Shigeo
Ifuka Toshihiro
Meguro Satoshi
Mima Hiroyuki
Hitachi Metals Ltd.
Tupper Robert S.
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