Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1999-09-20
2001-08-28
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S327100
Reexamination Certificate
active
06282067
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic reproducing head in use with computers, video/audio/data tape recorders, and disc devices. Particularly, the invention relates to a magnetic reproducing head in which signal detecting portions of which the number is equal to “the number of recorded tracks to be subjected to concurrent reproduction process+1” are disposed on a single magnetoresistive effect element, whereby the head structure is simplified, and plural pieces of information are separately and concurrently reproduced from a plurality of recorded tracks.
More particularly, the invention relates to a multi-channel magnetic-resistance-effect (MRE) thin-film magnetic head for high track density reproduction, in which the magnetic head includes domain control layers bonded onto one of the larger surfaces of a single magnetoresistive effect element, and detecting electrodes being in close contact with the surfaces of the domain control layers, while being disposed in opposition to the magnetoresistive effect element with respect to the domain control layers. The domain control layers are vertically disposed on a region of a magnetic recording medium, the region being located between adjacent recorded tracks on the magnetic recording medium. The number of the domain control layers is equal to “the number of recorded tracks±1”. The width of each domain control layer is shorter than the width of a space between adjacent recorded tracks on the magnetic recording medium. With such a unique technical feature, plural pieces of information are concurrently reproduced from the recorded tracks in the form of potential differences each between adjacent detecting electrodes. The unique technical feature accrues to the following advantageous results. A reproduced crosstalk for a recorded track, which leaks from a recorded track or tracks adjacent to the recorded track (this or those adjacent tracks will be referred to simply as an “adjacent track”), is satisfactorily suppressed. Reproduced noises are little generated. A reproduced signal that is output from the resultant magnetic head is high in level.
2. Description of the Related Art
Attempt has been made to realize a multi-channel MRE thin-film magnetic head for high track density reproduction which is capable of concurrently reproducing information from a plurality of recorded tracks even where the track pitch (= the distance between two adjacent recorded tracks) is narrow. Such a magnetic head is disclosed as a magnetic reproducing head in Japanese Patent Unexamined Publication No. Hei 8-263812, and shown in FIG.
12
.
The magnetic reproducing head disclosed in the publication is a multi-channel MRE thin-film magnetic head for high track density reproduction capable of concurrently reproducing information from a plurality of recorded tracks on a magnetic recording medium, such as a magnetic tape or a magnetic disc. The magnetic reproducing head includes a magnetoresistive effect element which is disposed crossing at least two recorded tracks on a magnetic recording medium, which the recorded tracks are to be subjected to concurrent reproducing process, and further detecting electrodes of which the number is equal to “the number of reproduced recorded tracks+1”. The magnetoresistive effect element allows a flow of an internal current in a direction which depends on a sense current fed thereto, and has an easy axis of magnetization longitudinally oriented. The detecting electrodes are bonded on one of the large surfaces of the magnetoresistive effect element while vertically disposed between the recorded tracks. The multi-channel MRE thin-film magnetic head detects potential differences each between two adjacent detecting electrodes, and produces those in the form of reproduced signals.
The operation of the magnetic reproducing head thus constructed will described with reference to
FIG. 12. A
bias magnetic field is applied from a bias magnetic thin film
27
to a magnetoresistive effect element
5
, while at the same time a sense current is fed to the same, whereby an initial state is set up in the magnetoresistive effect element. The bias magnetic field is directed upward or downward when viewed in the height directions of the magnetoresistive effect element (downward in FIG.
12
). With the application of the bias magnetic field, an angle
9
developed between 1) an orientation of an internal magnetization of the magnetoresistive effect element
5
, which is located in a region of a first channel (1st CH) defined between a first detecting electrode
8
and a second detecting electrode
9
, and
2
) an orientation of an internal current flowing through the magnetoresistive effect element
5
, satisfies 10°≦&thgr;80° or 100°≦&thgr;170°. In the specification, &thgr;=450.
The orientation of the internal magnetization of the magnetoresistive effect element
5
located in the 1 st CH region is rotated so that an angle &agr; between its orientation and the orientation of the internal current satisfies a relation 0°≦&agr;≦90°, in accordance with a magnitude of leaking flux by a signal (illustrated as a series of meshes and white stripes in
FIG. 12
) recorded in the first recorded track
2
on a magnetic recording medium
4
. As a result, resistance of the magnetoresistive effect element
5
located in the 1st channel region varies (FIG.
12
), and a reproduction voltage varies from B
1
(low resistance state)—K
1
(initial state)—A
1
(high resistance state) in accordance with the recording signal of a first recorded track
2
, to thereby form a first reproduced signal e
1
(FIG.
13
A).
Similarly, the angle, which is developed between an orientation of an internal magnetization of the magnetoresistive effect element
5
, which is located in a region of a second channel (2nd CH) defined between the second detecting electrode
9
and a third detecting electrode
10
, and an orientation of an internal current flowing through the magnetoresistive effect element
5
, is &thgr; in the initial state of the magnetic reproducing head.
The orientation of the internal magnetization of the magnetoresistive effect element
5
located in the 2nd CH region is rotated so that an angle &agr; between its orientation and the orientation of the internal current satisfies a relation 0°≦&agr;≦90°, in accordance with a magnitude of leaking flux by a signal (illustrated also as a series of meshes and white stripes) recorded in the second recorded track
3
on the magnetic recording medium
4
. As a result, resistance of the magnetoresistive effect element
5
located in the 2nd channel region varies, and a reproduction voltage varies from A
2
(high resistance state)—K
2
(initial state)—B
2
(low resistance state) in accordance with the recording signal of a second recorded track
3
, to thereby form a second reproduced signal e
2
(FIG.
13
B).
In such a simple multi-channel MRE thin-film magnetic head, improper magnetic domains are generated in a ferromagnetic material (mainly Ni-Fe) used for the magnetoresistive effect element, and the Bloch or domain walls shift in the reproducing operation, thereby causing called Barkhausen noises to generate. To cope with this, a MRE thin-film magnetic head for one-track reproduction is disclosed in U.S. Pat. No. 4,103,315. In the magnetic head, as shown in
FIG. 14
, an external magnetic field of which the orientation is coincident with an orientation of an initial magnetization in the single magnetoresistive effect element on the easy axis of magnetization of the magnetoresistive effect element, is applied to a magnetoresistive effect element. As a result, a single magnetic domain is formed in the magnetoresistive effect element.
In the magnetic head, antiferromagnetic thin films
32
, as shown in
FIG. 14
, are partially layered on both ends of a portion for sensing an external magnetic field (referred to as a magnetism sensing portion) of a magnetoresistive effect element
5
. A magnetic field directed in an orient
Hayashi Naoto
Kohro Makiko
Machida Kenji
Nagahara Shinichi
Numazawa Junji
Klimowicz William
Nippon Hoso Kyokai
Sughrue Mion Zinn Macpeak & Seas, PLLC
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