Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-10-12
2002-09-17
Ometz, David L. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S271000
Reexamination Certificate
active
06452760
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P11-291531 filed Oct. 13, 1999, which application is incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a magnetoresistive effect magnetic head which reads signals recorded on a magnetic recording medium by using magnetoresistive effect. The present invention also relates to a rotary magnetic head apparatus using the magnetoresistive effect magnetic head.
2. Prior Art
Conventionally, the helical scan method is proposed as a reproducing/recording method. This method uses a rotary magnetic head apparatus comprising a stationary drum, a rotary drum, and a magnetic head. The rotary drum is rotatively mounted with reference to the stationary drum. The magnetic head is mounted on the rotary drum. A magnetic tape is helically wound on the peripheral surface of the rotary magnetic head apparatus. As the rotary drum rotates, the magnetic head moves and slides touchingly across the magnetic tape for recording or reproducing signals on the magnetic tape.
According to the helical scan method, the magnetic head slides in contact with the running magnetic tape at a high speed for recording and reproducing signals. This provides a fast relative slide speed between the magnetic tape and the magnetic head, improving a data transfer rate.
Recently, in the helical scan method, a technology is proposed to use a magnetoresistive effect magnetic head (hereafter referred to as the MR head) for a reproducing head. The magnetoresistive effect magnetic head is widely used as a reproducing magnetic head for hard disk drives and the like.
An MR head is a magnetic head which reads signals from a magnetic recording an medium using magnetoresistive effect of a magnetoresistive effect element (hereafter referred to as the MR element). A pair of substrates is integrally joined through the intermediation of a gap. The gap contains a thin-film formed MR element which provides magnetoresistive effect. The width of the thin-film formed MR element determines the track width for the MR head, easily providing narrow tracks. The MR head provides high reproduction sensitivity because the MR element is exposed from a face opposite a magnetic recording medium.
Accordingly, it is expected to narrow recording tracks and record or reproduce signals with a higher density by using the MR head having the above-mentioned features as a reproducing head for the helical scan method.
A widely used MR head is of a shield type. This type of MR head contains an MR element formed in an inter-shield gap between a pair of magnetic shields. The shield type MR head provides better frequency characteristics and higher resolution than a non-shield type MR head which uses an MR element formed between a pair of nonmagnetic materials.
Widely known is the thin film shield-type MR head which uses a soft magnetic thin film for a pair of magnetic shields. By contrast, a substrate shield type MR head uses soft magnetic substrates for a pair of magnetic shields. Compared to this substrate shield type MR head, the thin film shield-type MR head provides easy control of a gap between a pair of magnetic shields, namely control of an inter-shield gap thickness, and excellent frequency characteristics.
According to the above-mentioned reasons, the thin film shield-type MR head is considered to be optimal as a reproducing head for the helical scan method.
Conventionally, an inductive bulk head is used for the helical scan method. When the thin film shield-type MR head is used as a reproducing head for the helical scan method, a pair of guard materials is integrally joined in the same manner as the inductive bulk head. A magnetic sensor is provided between the joint surfaces. The thin film shield-type MR head having this structure is formed optimally for the helical scan method.
Sometimes, a soft magnetic thin film as the magnetic shield is peeled off or a chip is damaged while the thin film shield-type MR head is formed to a shape optimal for the helical scan method. Using such a defective thin film shield-type MR head as a reproducing head for the helical scan method may damage a magnetic tape. Especially, in the helical scan method, the magnetic head fast slides in contact with the magnetic tape. When the thin film shield-type MR head as a reproducing head is defective, there is the high possibility of damaging the magnetic tape.
Recent research has shown that such a defect on the thin film shield-type MR head is caused by a thermal expansion coefficient difference between a substrate as a guard material and the soft magnetic thin film as a magnetic shield formed on this substrate.
It is a general practice to perform the heat treatment after forming the soft magnetic thin film as a magnetic shield for improving magnetic characteristics thereof The soft magnetic thin film differs from the substrate in thermal expansion coefficients. Because of this, while the soft magnetic thin film is heated, a stress is applied to these interfaces and may cause a crack. If an interface between the soft magnetic thin film and the substrate cracks, the shield thin film may peel off or a chip may be damaged during the process of forming the thin film shield-type MR head to a shape optimal for the helical scan method.
A strong stress is applied to easily crack the interface especially when there is a large contact area between the soft magnetic thin film and the substrate, namely, when the soft magnetic thin film is widely formed on the substrate.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in consideration of the foregoing. It is therefore an object of the present invention to provide an appropriate MR head as a reproducing head for the helical scan method. It is another object of the present invention to provide a rotary magnetic head apparatus using this MR head. Thereby, the soft magnetic thin film is prevented from being peeled off. Chips are prevented from being damaged.
In the magnetoresistive effect magnetic head according to the present invention, an inter-shield gap is formed between joint surfaces of a pair of guard materials through the intermediation of a pair of magnetic shield thin films. A magnetoresistive effect element is provided in the inter-shield gap. A groove is formed lengthwise at both lateral ends of a sliding surface opposite a magnetic recording medium. This groove restricts a contact width of the magnetoresistive effect magnetic head against the magnetic recording medium. The width of the pair of magnetic shield thin films is larger than the magnetoresistive effect element width and is smaller than the contact width.
Namely, the magnetoresistive effect magnetic head is configured to be of so-called thin film shield type. The width of a pair of magnetic shield thin films is larger than the magnetoresistive effect element width and is smaller than the contact width.
If the width of the pair of magnetic shield thin films is smaller than the magnetoresistive effect element width, a sufficient magnetic shield effect is unavailable. If the width of the pair of magnetic shield thin films is too large, a large contact area results between the magnetic shield thin film and the guard material. These interfaces may crack due to differences in thermal expansion coefficients. This may cause the magnetic shield thin film to peel off or the guard material to be damaged.
In the magnetoresistive effect magnetic head according to the present invention, the width of the pair of magnetic shield thin films is larger than the magnetoresistive effect element width and is smaller than the contact width. The magnetic shield thin film can provide a sufficient magnetic shield effect. A contact area can be controlled between the magnetic shield thin film and the guard material. This effectively suppresses cracks on the interfaces and prevents the magnetic shield thin film from peeling off and the guard material from being damaged.
The rotary magnetic head apparatus
Inaguma Teruo
Nakashio Eiji
Onuma Kazunori
Ometz David L.
Sonnenschein, Nath & Roesnthal
Sony Corporation
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