Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-12-28
2003-07-08
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603010, C029S603070, C029S603130, C029S603140, C029S603150, C360S125330, C360S125020, C148S121000, C148S122000
Reexamination Certificate
active
06588092
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic head which is satisfactory in the anti-corrosion characteristic and the input and output characteristic, and is sufficiently durable against cracking in a base thereof; a method for producing the magnetic head; a video recording and reproduction apparatus including the magnetic head, and a video camera including the magnetic head.
2. Description of the Related Art
As a magnetic head for VCRs or the like, a ferrite head including a magnetic core formed by combining a pair of ferrite sections together is conventionally used. Recently, in accordance with the improvement in the magnetic recording density, a metal-in-gap head (MIG head) has become often used. The MIG head uses a metal magnetic material having a more highly saturated magnetic flux density than that of ferrite for a portion in the vicinity of a recording/reproduction gap.
FIG. 8
schematically shows an exemplary conventional ferrite head
300
. FIGS
9
A through
9
D schematically show an exemplary conventional MIG head
400
.
With reference to
FIG. 8
, the ferrite head
300
includes a pair of ferrite sections F
1
A and F
1
B, and a nonmagnetic layer N
1
and glass bonding sections G
1
both provided between the pair of ferrite sections F
1
A and F
1
B for combining the ferrite sections F
1
A and F
1
B.
With reference to
FIGS. 9A through 9D
, the MIG head
400
includes a pair of magnetic core halves MCA and MCB, and a nonmagnetic layer N
2
and glass bonding sections G
2
both provided between the pair of magnetic core halves MCA and MCB for combining the magnetic core halves MCA and MCB. The magnetic core half MCA includes a ferrite section F
2
A, at least one underlying layer (not shown) provided on the ferrite section F
2
A, and a metal magnetic thin film FM
2
provided between the underlying layer and the nonmagnetic layer N
2
. The magnetic core half MCB includes a ferrite section F
2
B, at least one underlying layer (not shown) provided on the ferrite section F
2
B, and a metal magnetic thin film FM
2
provided between the underlying layer and the nonmagnetic layer N
2
.
As a material for the metal magnetic thin films FM
2
, amorphous materials (e.g., Japanese Laid-Open Publication No. 63-120653), Fe—N-based materials, and Fe—C-based materials have been developed. The Fe—N-based materials and Fe—C-based materials are obtained by thermally treating an amorphous film mainly containing Fe to deposit microscopic crystals having a diameter of about 5 to about 20 nm (e.g., Hasegawa, Journal of the Magnetics Society of Japan, 14, pp. 319-322 (1990); and Nago, IEEE, Trans., Magn., Vol, 28, No. 5 (1992)).
Among these materials, materials obtained by depositing or growing microscopic crystalline particles having a magnetic metal composition and thus having a highly saturated magnetic flux density of 1.2 T or higher and a soft magnetic characteristic need to be improved in the anti-corrosion characteristic.
For this purpose, attempts have been made to add light elements having passivity to these materials. However, the light elements, which easily react with oxygen, nitrogen and the like, react with oxygen used for making crystals amorphous or microscopic and thus tend not to remain in the microscopic crystalline particles having the magnetic metal composition.
In order to overcome this problem, in addition to adding the light elements having passivity to the above-mentioned metal magnetic materials, the magnetic crystalline particles of these materials are each controlled to have a relatively large size and a relatively large surface area. The metal magnetic thin film thus developed has satisfactory magnetic characteristics, a highly saturated magnetic flux density, and a sufficient anti-corrosion characteristic (e.g., Japanese Laid-Open Publication No. 10-223435).
An MIG head is a composite device of ferrite, which is an oxide, and a metal magnetic thin film. Accordingly, the MIG head involves the problems that the ferrite base may be cracked by an internal stress generated in the metal magnetic thin film and that the magnetic characteristics may be deteriorated by a reaction at the interface between the ferrite base and the metal magnetic thin film. The above-mentioned problems are caused by the structure of the MIG head or the material characteristics of the metal magnetic thin film.
An optimum structure of a magnetic head varies in accordance with the material characteristics of the metal magnetic thin film. In order to improve the characteristics of the magnetic head, it is necessary to solve the problems of the cracks in the ferrite base and the deterioration of the magnetic characteristics as well as to improve the materials design.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a magnetic head includes a pair of magnetic core halves; and a nonmagnetic layer provided between the pair of magnetic core halves for combining the pair of magnetic core halves. The pair of magnetic core halves each includes an oxide magnetic base, at least one underlying layer provided on the oxide magnetic base, and a metal magnetic thin film provided between the underlying film and the nonmagnetic layer. The metal magnetic thin film includes a magnetic film containing, as a major material, magnetic crystalline particles having an average volume Va and an average surface area Sa fulfilling the relationship of Sa>about 4.84 Va
⅔
. At least one of the pair of magnetic core halves has a winding window therein. The metal magnetic thin film is provided in such a manner as to prevent the oxide magnetic base from cracking due to an internal stress generated in the metal magnetic thin film.
In one embodiment of the invention, the metal magnetic thin film includes magnetic crystalline particles, which have an average length of a longer side of more than about 50 nm.
In one embodiment of the invention, the magnetic crystalline particles have at least one shape selected from the group consisting of a generally needle-like shape, a generally column-like shape, and a multiple-branch shape including the magnetic crystalline particles of the generally needle-like shape and the generally column-like shape; and the magnetic crystalline particles having the generally needle-like shape and the generally column-like shape have an average length of a shorter side of more than about 5 nm and less than about 60 nm.
In one embodiment of the invention, where dS is an average length of a shorter side of the magnetic crystalline particles and dL is an average length of a longer side of the magnetic crystalline particles, 5 nm<dS<60 nm and 60 nm<dL<5000 nm.
In one embodiment of the invention, the metal magnetic thin film has a composition represented by (M
a
X
b
Z
c
)
100-d
A
d
, where M includes at least one magnetic metal element selected from the group consisting of Fe, Co and Ni; X includes at least one element selected from the group consisting of Si, Al, Ga and Ge; Z includes at least one element selected from the group consisting of elements of group IVa, elements of group Va, Al, Ga and Cr; A includes at least one element selected from the group consisting of O and N; and a, b, c and d fulfill the relationships of about 0.1≦b≦about 26, about 0.1≦c≦about 5, a+b+c=100, and about 1≦d≦about 10.
In one embodiment of the invention, the pair of magnetic core halves each have a combining surface which is combined with the other magnetic core half with the nonmagnetic layer interposed therebetween, a recording medium running surface on which a recording medium runs, and outer side surfaces continuous from the combining surface and from the recording medium running surface; and the metal magnetic thin film is not provided on the outer side surfaces.
In one embodiment of the invention, the metal magnetic thin film has a composition represented by (Fe
a
Si
b
Al
c
T
d
)
100-e
N
e
where T includes at least one element selected from the group consisting of Ti and Ta; and a, b, c, d and e fulfi
Hiramoto Masayoshi
Matsukawa Nozomu
Osano Koichi
Sakakima Hiroshi
Sawai Eisuke
Arbes Carl J.
Matsushita Electric - Industrial Co., Ltd.
Nguyen Tai
Renner , Otto, Boisselle & Sklar, LLP
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