Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-06-28
2002-10-15
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S119050, C360S125330
Reexamination Certificate
active
06466415
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a thin film magnetic head, a magnetic head device, a magnetic disk driving device and a method for manufacturing a thin film magnetic head.
2. Related Art Statement
A floating type thin film magnetic head to be used in a magnetic recording/reproducing device of a computer has at least one recording element and at least one reading element on the air outflow side of the slider thereof. As the recording element, an inductive type magnetic conversion type element is generally used, and as the reading, a magnetic conversion element using a magnetic resistive effect is used.
For realizing a high recording density in a magnetic disk using this kind of thin film magnetic head, it is required that data amount (surface recording density) to be restored in the unit area of the magnetic disk is enhanced. The surface recording density depends on the performance of the recording element, and can be enhanced by shortening the gap length between the recording poles of the recording element.
The surface recording density can be also enhanced by increasing the track number to be recorded in the magnetic disk. The track number recordable in the magnetic disk is normally represented as “TPI (track per inch)”. The TPI performance of the recording element can be enhanced by downsizing the recording head to determine the width of the data track. The size of the recording head is normally known as a track width.
However, the shortening of the gap length between the recording poles and the narrowing of the track width decrease the magnetic flux in between the recording poles, resulting in the degradation of the overwrite performance. Therefore, in view of recording performance, the shortening of the gap length and the narrowing of the track width can not employed for a high density recording magnetic disk having a high coercivity Hc.
To solve this problem, the recording pole structure, in which in a recording pole portion, a magnetic film having a high saturated magnetic flux density (a first magnetic film) is provided adjacent to a gap film and a second magnetic film having a smaller saturated magnetic flux density than the first magnetic film is provided on the first magnetic film, is suggested and practically used. For example, the specification of U.S. Pat. No. 5,606,478 discloses that the part of the recording pole portion adjacent to the gap film is made of a magnetic material having a higher saturated magnetic flux, for example Ni
55
Fe
45
, than the magnetic material having a NiFe composition which is usually used for the pole portion of the above thin film magnetic head.
In addition, the specification of Kokai Publication Kokai Hei 5-73839 (JP A 5-73839) discloses that an underfilm to plate a bottom magnetic core and a top magnetic core is made of a magnetic material having a higher saturated magnetic flux density than the magnetic materials constituting the bottom magnetic core and the top magnetic core.
The recording element composed of the inductive type magnetic conversion element generally has a first pole portion, a gap film, a coil film, an insulating film and a second pole portion. The first pole portion is composed of a magnetic film which extends backward from a medium opposing surface. The gap film is provided adjacent to the first pole portion, and the second pole portion is provided adjacent to the gap film. The second pole portion is composed of a magnetic film which extends backward from the medium opposing surface and joined with the magnetic film constituting the first magnetic pole portion at its rear portion. The coil film is embedded in the insulating film, and winds up vertically the joining portion of the first and second pole portions.
In a relatively primary type pole structure, the magnetic film extended from the second pole portion used to be, as a yoke portion, formed on the organic insulating material to support the coil film. The organic insulating film is inclined and rose up, between the pole portion and the yoke portion, at a given angle on the gap film. Therefore, the magnetic film to be formed on the organic insulating film is also inclined alongside the inclined portion at the given angle of the organic insulating film. The inclination starting point of the magnetic film is called as a “Throat Height zero point”, and the inclination angle is called as a “Apex Angle”. The magnetic film formed on the organic insulating film constitutes the second pole portion parallel to the gap film to the Throat Height zero point from its forefront in the air bearing surface, inclined at the Apex Angle from the Throat Height zero point, and continues to the yoke portion.
The throat Height zero point directly contributes to the electro-magnetic conversion characteristics of the recording element, so required to be controlled precisely. Moreover, the Apex Angle is required to be set to a small value so as not to be saturated magnetically for transmitting a magnetic flux generated from a writing current in the coil film effectively to the pole portion.
In the conventional pole structure in which the magnetic film extended from the second pole portion is formed on the organic insulating film, however, since the inclination starting point and inclination angle of the organic insulating film changes due to its applying process and baking process, it is difficult to control and set the Throat Height zero point. And the Apex Angle becomes relatively large.
The specifications of U.S. Pat. No. 5,606,478 and Kokai Publication Kokai Hei 5-73839 which are proposed as a high density recording means do not teach to decrease the Apex Angle.
For ironing out the above problem, for example, the specification of Kokai Publication Kokai Hei 7-225917 (JP A 7-225917) discloses that the second pole portion and its yoke portion are formed independently. In this case, since the rising start point of the yoke portion corresponds to the Throat Height zero point, the Throat Height zero point can be controlled and set high precisely.
However, the insulating film to support the coil film has its inclined surface. Therefore, the decreasing of the Apex Angle of the yoke portion continuing the second pole portion is restricted, so that the magnetic flux transmission efficiency for the pole portion and the overwrite characteristic can not be much improved.
Moreover, the specification of Kokai Publication Kokai Hei 7-267776 (JP A 267776) discloses that in the above pole structure in which the second pole portion and the yoke portion thereof are formed independently, the insulating film to support the coil film is flattened so that its surface can have the same level as that of the second pole portion, and the yoke portion to continue the second pole portion is formed on the flattened surface of the insulating film. In this case, since the edge portion of the second pole portion corresponds to the Throat Height zero point, the Throat Height zero point can be set precisely.
However, since the edge portion of the second pole portion is almost orthogonal to the gap film and the almost orthogonal angle for the gap film corresponds to the Apex Angle, the magnetic flux transmission efficiency for the pole portion and the overwrite characteristic can not be much improved.
Furthermore, Kokai publication Kokai Sho 60-193114 (JP A 60-193114) discloses that a depressed portion is formed on the surface of the slider substrate and a magnetic film continuing the first pole portion is formed in the depressed portion to manufacture a thin film magnetic head having a low step structure. In this case, however, it is difficult to control the Throat Height zero point precisely.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a thin film magnetic head having a recording pole structure of high recording performance.
It is another object of the present invention to provide a thin film magnetic head having a recording pole structure to be used for high density recording.
It is still another object of the present invention to
Ito Noriyuki
Kanakubo Katsuya
Mino Tetsuya
Terunuma Koichi
Evans Jefferson
Oliff & Berridg,e PLC
TDK Corporation
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