Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-12-27
2004-09-21
Tupper, Robert S. (Department: 2622)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06795271
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic head for a magnetic recording/reproduction apparatus and a magnetic recording/reproduction apparatus, and more specifically to a recording head, a combined head and a magnetic recording/reproduction apparatus in which a fluctuation in reproduction characteristics is suppressed even in the case where a material having great saturation magnetization which realizes high recording ability is used for a magnetic core.
2. Description of the Related Art
In accordance with a trend of minimization and enlarging capacity of a magnetic memory device, a volume of per one bit to be recorded on a magnetic medium becomes smaller quickly.
A magnetoresistive effect type head (hereinafter, “MR head”) can detect a magnetic signal generated from this minute bit as a large reproduction output.
This MR head is discussed as “A Magnetoresistivity Readout Transducer” in “IEEETrans. on Magn,. MAG7 (1971) 150”.
Recently, a great magnetoresistive (hereinafter, “GMR”) head using GMR which can realize greatly high output for the MR head has been put into practical use.
In this GMR effect, particularly a magnetoresistive effect which is generally called as a spin-valve effect, in which a change in resistance corresponds to cosine between magnetization directions of two adjacent magnetic layers, shows a great change in resistance in a weak operating magnetic field. For this reason, the GMR head using this effect is a generic name of “GMR head”.
This GMR head using the spin-valve effect is discussed as “Design, Fabrication & Testing of Spin-Valve Read Heads for High Density Recording” in “IEEE Trans. on Magn,. Vol.30,No.6 (1994)3801”.
As for the above GMR head, one magnetic layer of two magnetic layers for producing the spin-valve effect has a magnetization fixed layer where magnetization is fixed so as to be substantially aligned with a direction along which a magnetic field of a medium entering into a head magnetic sensing portion by an exchange coupling magnetic field which is generated by laminating an antiferromagnetic film on the one magnetic layer.
The other magnetic film, which is adjacent to the magnetization fixed layer via a conductive layer made of Cu or the like, is a magnetization free layer in which the magnetization direction can be changed freely with respect to the magnetic filed of the medium. Hereinafter, the GMR head using the spin-valve effect is called as “GMR head”.
FIGS. 6 and 7
are structural diagrams showing concrete examples of a conventional combined head
50
which is composed of a GMR reproduction head
70
and an ID recording head
60
.
FIG. 7
is a diagram of the structure of the GMR head viewed from an air bearing surface (ABS surface) which is a surface opposed to the magnetic medium.
FIG. 6
is a cross section taken along a line A-B of FIG.
7
.
Namely, a magnetic separation layer
3
made of an insulating material intervenes between a lower shield
2
and an upper shield
6
which are laminated on a ceramic
1
to be used as a slider, and a spin-valve laminated structure for producing the GMR effect is arranged as a center area
4
. An end portion area
5
for supplying an electric current and a bias magnetic field is formed at both the ends of the center area
4
. These are GMR elements for reproduction.
Further, the upper shield is used as a first magnetic core
6
, and a second magnetic core
11
is arranged on a surface of the magnetic core
6
which is opposite to the GMR elements via a recording gap
7
.
Coils
9
, which are sandwiched between the recording gap film
7
, a non-magnetic insulating material
10
a
and a non-magnetic insulating material
10
b
, are arranged in slightly inner portions of the magnetic cores
6
and
11
from ABS.
Recording is carried out by magnetic flux which leaks from the recording gap
7
between the magnetic cores
6
and
11
magnetized by magnetic fields generated from the coils.
The above combined-structure head, in which the GMR or MR reproduction head and the inductive (hereinafter “ID”) recording head are stacked to each other, is called as a combined head here.
A recording density which is actually used by the combined head using GMR has a high-density recording area of not less than 3 GB per inch. A conventional combined head using a material having magnetic anisotropy is sufficient for recording density less than the above density.
Namely, the practical combined head using GMR realizes magnetic recording/reproduction with high density of not less than 3 GB per 1 square inch.
In the reverse way, a magnetic recording/reproduction apparatus which is structured by using the combined head of GMR is an apparatus for carrying out recording/reproduction with high density of 3 GB per 1 square inch.
An ID head which takes responsibility for recording onto a magnetic medium is always required for improvement of a high-density recording. Particularly, a high coercive force of a magnetic medium is essential for high-density recording.
This is because a magnetization transition length to be recorded on a medium is made to be shorter in accordance with the improvement of the recording density, or the magnetization is kept constant even if a magnetization length for 1 bit becomes shorter.
For this reason, a technique for increasing a recording magnetic field has been conventionally developed energetically so that recording can be carried out onto high coercive force medium as an ID head which is suitable for high-density recording.
Conventionally, an Ni—Fe plated film (hereinafter, permalloy) in which Ni is about 80 weight % has been used as a magnetic core of the ID head. This material has saturation magnetization (Bs) of about 1T (tesla), and recording of 3 GB per 1 square inch can be carried out. This is described in “3 Gb/in
2
recording demonstration with dual element heads & thin film disks” of “IEEE Trans. on Magn,. Vol.32, No.1 (1996) pp. 7-12”.
However, in order to carry out recording of not less than 5 GB per 1 square inch, an Ni—Fe plated film in which Ni is about 45 weight % (hereinafter, 45 NiFe) is required instead of the permalloy. This is described in “5 Gb/in
2
recording demonstration with conventional ARM dual element heads & thin film disks” of “IEEEE Trans. on Magn,. Vol.33, No.5 (1997) pp. 2866-2871”.
This material has saturation magnetization of about 1.6T (tesla) maximally. Moreover, with this material, recording of about 12 GB per 1 square inch can be carried out. This is described in “12 Gb/in
2
recording demonstration with SV read heads & conventional narrow pole-tipwrite” of “IEEE Trans. on Magn,. Vol. 32, No. 1 (1996) pp. 7-12”.
Meanwhile, examples using an Ni—Fe plated film in which Bs is about 1.6 are disclosed in the Japanese Unexamined Patent Publication (KOKAI) Nos. 8-212512 (1996) and 11-16120 (1999).
In addition, an example using a high saturation magnetization Bs material formed by a sputtering method is disclosed in the Japanese Unexamined Patent Publication (KOKAI) No. 10-162322 (1998), and in this example, a Co amorphous film represented by a Co—Ta—Zr sputtering film is used.
The Co amorphous film can have high Bs up to about 1.5T. Moreover, the Japanese Unexamined Patent Publication (KOKAI) No. 7-262519 (1995) discloses an application of high Bs materials such as ferric nitride. It is considered that an iron-nitrogen material can have high Bs of about 1.9T.
Further, in the case where simplicity and cost reduction of a manufacturing process for a magnetic head are considered, it is effective to form a magnetic material forming a recording magnetic pole according to a plating method.
In the plating method, a photoresist frame through which a form of a magnetic pole previously pierces is formed, and a plated film is allowed to grow in the frame so that a desired pattern can be obtained. Because of the simplicity and cost reduction of this method, this method is currently a standard manufacturing method of a thin film magnetic head.
Meanwhile, in the case where a magnetic core pattern is formed by the s
Honjo Hiroaki
Ishi Tsutomu
Ishiwata Nobuyuki
Nonaka Yoshihiro
Ohashi Keishi
NEC Corporation
Tupper Robert S.
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