Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1999-11-22
2002-09-17
Miller, Brian E. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06452759
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a yoke-type magnetoresistive (MR) head, a yoke-type MR composite film head, and a magnetic storage apparatus using the same.
2. Description of the Related Art
Recently, with the rapid development of the computer processing capability, a magnetic recording medium such a hard disk is desired to increase the data transfer rate. In order to realize this, a magnetoresistive type magnetic head has been playing a significant role.
Originally, the magnetic head using the magnetoresistive (MR) head was dedicated for production (information reading). However, the magnetic storage apparatus requires a head capable of not only reproduction but also recording (write in). For this, a shield type MR head and a yoke type MR head have been developed and examined.
In the shield type MR head as shown in FIG. 6 of Japanese Patent publication A63-205584, an MR pattern (magnetoresistive element) is sandwiched by a soft magnetic shield, and adjacent to the shield, an electromagnetic induction type recording head is arranged.
FIG. 17
is a cross sectional view showing a configuration of the conventional shield type MR head. In the conventional shield type MR head
101
an MR pattern (magnetoresistive element)
105
is arranged via an MR insulation layer
104
made from a non-magnetic material such as oxide and sandwiched by a lower shield layer
102
made from a soft magnetic material and a common pole
103
made from a soft magnetic material. The conventional shield type MR head
101
further includes an electromagnetic induction type recording head constituted by the common pole
103
, an upper pole
106
, and a coil pattern
107
. One end of the MR pattern
105
is exposed to a head air bearing surface (ABS). The common pole
103
and the upper pole
106
are magnetically connected at their rear ends (opposite to the head ABS side). It should be noted that the reference symbol
108
denotes a non-magnetic layer made from an oxide or the like. This non-magnetic layer
108
constitutes a recording gap serving for electrical insulation between the coil pattern
107
and the common pole
103
. The reference symbol
109
is a layer for covering a stepped portion. This stepped portion coverage layer coves a stepped portion formed by the coil pattern
107
and serves for electric insulation between the coil pattern
107
and the upper pole
106
.
The yoke type MR head provides a hollow space at a portion of the yoke constituting the magnetic head and an MR pattern (magnetoresistive element) is arranged in the vicinity of this hollow space.
FIG. 18
is a cross sectional view showing a configuration of a conventional yoke-type MR head. The conventional yoke type MR head
201
includes a lower pole
202
, an upper pole front part
203
, an upper pole rear part
204
, an MR pattern (magnetoresistive element)
205
, and a coil pattern
206
. The reference symbol
207
denotes a non-magnetic layer made from an oxide or the like. This non-magnetic layer
207
forms a gap between the lower pole
202
and the upper pole front part
203
. The upper pole rear part
204
and the lower pole
202
are magnetically connected at the rear side (opposite to the head air bearing surface). The reference symbol
208
denotes a gap provided between the upper pole front part
203
and the upper pole rear part
204
. The MR pattern
205
is arranged in the vicinity of this gap
208
. The lower pole
202
and the upper pole rear part
204
are magnetically connected at the rear part (opposite to the head air bearing surface). Symbol
209
denotes a stepped portion coverage layer made from a non-magnetic material.
As shown in
FIG. 18
, in the conventional yoke type MR head
201
, a gap
208
is present in a portion of the yoke pattern constituted by the lower pole
202
, the upper pole front part
203
, and the upper pole rear part
204
. Accordingly, there is a defect that a magnetic flux cannot effectively pass through during recording. To eliminate this defect, Japanese Patent Publication A3-66015 suggests a composite type thin film magnetic head which includes a center pole (not depicted) in the vicinity of the gap
208
, so as to increase the recording efficiency.
In the conventional shield type MR head as shown in
FIG. 17
, the MR pattern is partially exposed to the ABS plane (head air bearing surface) where the magnetic head faces a recording medium. Accordingly, when the recording medium is brought into contact with the MR pattern, the MR pattern generates a noise. This noise generation phenomenon is called thermal asperity. In a recent magnetic storage apparatus, in order to increase the recording density, the head flying height is minimized for the recording medium. When the head flying height is decreased, the medium is brought into contact with the head more frequently, often causing thermal asperity of the reproduction output. That is, in a higher density recording, thermal asperity noise tends to increase. For this, the magnetic storage apparatus using the conventional shield type MR head may lower reliability.
The cause of the thermal asperity in a reproduction signal of the conventional shield type MR head can be explained as follows. During a magnetic recording, the MR head and the medium relatively move at a high speed equal to above 10 m per second. Here, if the magnetic head flowing amount is small and is brought into contact with the MR pattern of the head, the collision generates a friction head so that the MR pattern temperature is instantaneously increased. When the MR pattern temperature is increased, its component, i.e., ferromagnetic metal thin film increase resistance. In a detection circuit reading an information item by converting into voltage the resistance change in the MR pattern signal magnetic field, the resistance change by heat generation is erroneously read as a signal. Moreover, the heated MR pattern has a great cooling time constant compared to an ordinary signal waveform. Until the MR pattern is cooled down, a great DC-like bias voltage is applied to the signal, which greatly shifts the detection level. This may cause a signal burst error.
Furthermore, another thermal asperity is involved. In the MR head a sense current is constantly applied to the MR pattern. For this, the MR pattern constantly generates some heat. When the medium is brought into contact with the MR pattern and the collision energy is not so large, the heat of the MR head moves to the medium, the MR pattern temperature is instantaneously lowered. This temperature lowering reduces the resistance of the MR pattern, which may cause a signal magnetic field detection error. In either case, the conventional shield type MR head has a configuration which easily cases the thermal asperity as a first problem.
The second problem of the shield type MR head is that the magnetic recording element and the reproduction element are not aligned at the same position on the ABS plane. Accordingly, the recording track position and the reproduction track position are slightly different. Consequently, the magnetic disk apparatus should have a servo circuit to correct the difference.
These first and second problems can be improved by the yoke type MR head shown in FIG.
18
. In the yoke type MR head, in order to solve the problems of thermal asperity, the MR pattern is located at a position far from the ABS plane. This configuration allows to use the yoke as a recording head having a gap, and generation of the recording magnetic field is significantly low. On the other hand, with increase of the magnetic recording density, the coercive force Hc of the recording medium tends to be increased. This leads to a high magnetic field intensity from the magnetic head required for recording. However, the conventional yoke type MR head cannot generate a sufficiently high magnetic field intensity and is not preferable for a high density recording. This is a third problem.
The third problem is caused as follows. As shown in
FIG. 18
, in the yoke type MR head, the MR pa
Chen Tianjie
Miller Brian E.
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