Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1998-06-18
2002-06-04
Klimowicz, William (Department: 2752)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S319000, C360S322000
Reexamination Certificate
active
06400537
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head employing a magnetoresistance effect device (hereinafter, referred to as an MR device). In particular, the present invention relates to a thin film magnetic head for significantly high density magnetic recording having a remarkably narrow shield gap length.
2. Description of the Related Art
A thin film magnetic head employing an MR device have long been under development.
FIG. 6
shows a cross-sectional view of a thin film magnetic head having a conventional MR device.
The conventional thin film magnetic head
200
includes a recording head section
180
and a reproducing head section
190
. The recording head section
180
includes head cores
12
and
13
formed of magnetic substances, and a recording gap
14
formed of a non-magnetic insulating film. In addition, a winding conductor
11
is provided through the non-magnetic insulating film. In the recording head section
180
, a magnetic field generated by current flowing through the winding conductor
11
is converged to the head cores
12
and
13
, and thus recording to a medium is performed by the magnetic field leaked from the recording gap
14
. This type of recording head section
180
is referred to as an inductive type recording head.
On the other hand, the reproducing head section
190
includes an upper shield
13
(functioning as the recording head core
13
) and a lower shield
16
formed of magnetic films, and an MR device section
15
in a shield gap
17
between the upper and lower shields
13
and
16
. The MR device section
15
is insulated from the upper shield
13
and the lower shield
16
by insulating films
18
. A lead section
19
is formed so as to supply current in a direction of the plane of the thin film MR device section
15
. Conventionally, as a material for the MR device section
15
, a permalloy (e.g., Ni
0.8
Fe
0.2
) is used. The reproducing head section
190
, which is a magnetoresistance effect type head, detects a change in a signal magnetic field from a medium as a change in the electric resistance of the MR device section
15
, and this makes it possible for the head section
190
to read out a signal recorded in the medium.
However, the following problems arise in achieving high density recording when the conventional technique described above is used. Since a shield gap length (denoted by d
sg
in
FIG. 6
) is required to be equal to or shorter than the shortest signal wavelength to be reproduced, it is necessary to further reduce the thicknesses of the insulating films
18
and the MR device section
15
with further development of high density recording. In the future, the shield gap length is expected to be about 100 nm or less, and there will be a need for the thickness of the insulating film
18
to be about 50 nm or less. However, to the detriment of achieving high density recording, it is technically difficult to form an insulating film having a thickness of about 50 nm or less and maintain good insulating properties.
SUMMARY OF THE INVENTION
A thin film magnetic head according to the present invention includes an upper shield section, a lower shield section and a magnetoresistance device section. The magnetoresistance device section is between the upper shield section and the lower shield section. The magnetoresistance device section is connected to the upper shield section and the lower shield section through conductive layers. Current flows through the magnetoresistance device section via the upper shield and the lower shield.
In one embodiment of the invention, the magnetoresistance device section includes a multilayer structure exhibiting a giant magnetoresistance effect.
In another embodiment of the invention, the current flows in a direction substantially perpendicular to a plane of the multilayer structure.
In still another embodiment of the invention, the multilayer structure includes a soft magnetic film. The magnetization easy axis of the soft magnetic film is substantially orthogonal to a direction of a magnetic field to be detected.
In yet another embodiment of the invention, the multilayer structure includes a hard magnetic film, a soft magnetic film and a non-magnetic film formed between the hard magnetic film and the soft magnetic film. The magnetization easy axis of the hard magnetic film substantially agrees with a direction of a magnetic field to be detected.
In one embodiment of the invention, the thin film magnetic head further includes an interface magnetic film mainly composed of Co having a thickness of about 0.1 to 1 nm at least one of interfaces between the non-magnetic film and the hard magnetic film and between the non-magnetic film and the soft magnetic film.
In another embodiment of the invention, the magnetoresistance device section includes a plurality of multilayer structures.
In still another embodiment of the invention, the magnetoresistance device section includes a plurality of multilayer structures.
In yet another embodiment of the invention, the magnetoresistance device section further includes a non-magnetic film between the plurality of multilayer structures.
In one embodiment of the invention, the magnetoresistance device section further includes a non-magnetic film between the plurality of multilayer structures.
In another embodiment of the invention, the multilayer structure includes a metal anti-ferromagnetic film, a first magnetic film magnetically coupled to the metal anti-ferromagnetic film, a soft magnetic film and a non-magnetic film formed between the first magnetic film and the soft magnetic film in this order. The magnetization easy axis of the first magnetic film substantially agrees with a direction of a magnetic field to be detected.
In still another embodiment of the invention, the multilayer structure further includes an interface magnetic film mainly composed of Co having a thickness of about 0.1 to 1 nm at least one of interfaces between the non-magnetic film and the first magnetic film and between the non-magnetic film and the soft magnetic film.
In yet another embodiment of the invention, the magnetoresistance device section includes a plurality of multilayer structures.
In one embodiment of the invention, the magnetoresistance device section includes a plurality of multilayer structures.
In anther embodiment of the invention, the magnetoresistance device section further includes a non-magnetic film between the plurality of multilayer structures.
In still another embodiment of the invention, the magnetoresistance device section further includes a non-magnetic film between the plurality of multilayer structures.
In yet another embodiment of the invention, the non-magnetic film includes a first non-magnetic film, a second non-magnetic film and a third non-magnetic film interposed between the first non-magnetic film and the second non-magnetic film. The second non-magnetic film has a thickness of about 0.1 to 1 nm and is formed of a different material from the first non-magnetic film and the second non-magnetic film.
In one embodiment of the invention, the non-magnetic film includes a first non-magnetic film, a second non-magnetic film and a third non-magnetic film interposed between the first non-magnetic film and the second non-magnetic film. The second non-magnetic film has a thickness of about 0.1 to 1 nm and is formed of a different material from the first non-magnetic film and the second non-magnetic film.
In another embodiment of the invention, the soft magnetic film is mainly composed of Ni
x
Co
y
Fe
z
, where X is 0.6 to 0.9, Y is 0 to 0.4 and Z is 0 to 0.3 in an atomic composition ratio.
In still another embodiment of the invention, the soft magnetic film is mainly composed of Ni
x′
Co
y′Fe
z′
, where X′ is 0 to 0.4, Y′ is 0.2 to 0.95 and Z′ is 0 to 0.5 in an atomic composition ratio.
In yet another embodiment of the invention, the soft magnetic film is formed of an amorphous material.
In one embodiment of the invention, the non-magnetic film is formed of any
Irie Yousuke
Kawawake Yasuhiro
Sakakima Hiroshi
Satomi Mitsuo
Klimowicz William
Renner , Otto, Boisselle & Sklar, LLP
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