Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1999-05-18
2001-01-09
Pianalto, Bernard (Department: 1762)
Stock material or miscellaneous articles
Composite
Of inorganic material
C360S110000, C427S128000, C427S132000, C428S702000, C428S704000, C428S900000
Reexamination Certificate
active
06171716
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to soft magnetic films for use as, for example, magnetic layers in thin film magnetic heads, and magnetic cores in inductors or the like, and more particularly, to soft magnetic films in which a magnetostriction constant can be reduced while maintaining soft magnetic properties and to thin film magnetic heads, planar magnetic elements (e.g., transformers and inductors), and filters using the soft magnetic films.
2. Description of the Related Art
For soft magnetic films used as magnetic layers in thin film magnetic heads, planar magnetic elements (e.g., transformers and inductors), or magnetic cores in filters or the like, materials having excellent soft magnetic properties such as resistivity and magnetic permeability, particularly at high frequencies, are required.
An Fe—M(such as Zr, Hf, and Ta)—O system alloy film is considered to be a soft magnetic film having excellent high frequency characteristics. Since this soft magnetic film has high resistivity, eddy current loss can be reduced. The film also exhibits high magnetic permeability at high frequency bands.
However, the Fe—M(such as Zr, Hf and Ta)—O system alloy has a high magnetostriction constant, specifically, of approximately 4×10
−6
to 6×10
−6
.
It is thought that the Fe—M(such as Zr, Hf, and Ta)—O system alloy film includes a fine crystalline phase having a bcc structure containing mainly Fe and an amorphous phase, which surrounds the fine crystalline phase, composed of the oxide of the element M such as Hf. Therefore, presumably it is mainly the fine crystalline phase containing a large amount of Fe that generates magnetism. The reason for an increase in magnetostriction of the soft magnetic film is that Fe which constitutes the fine crystalline phase has large magnetostriction. Additionally, since the fine crystalline phase is not composed of Fe alone and also contains impurities such as Hf and O, the impurities are considered to affect the magnetostriction of the soft magnetic film.
When the Fe—M(such as Zr, Hf, and Ta)—O system alloy having a high magnetostriction constant is used for magnetic layers in thin film magnetic heads or magnetic cores in inductors, soft magnetic properties such as magnetic permeability of the soft magnetic films are easily degraded. Additionally, because of the relationship between internal stress and magnetostriction in the deposited soft magnetic film, the degradation of soft magnetic properties or the separation of the film easily occurs in the soft magnetic film.
SUMMARY OF THE INVENTION
The present invention overcomes the difficulties noted above with respect to the conventional art. It is an object of the present invention to provide soft magnetic films in which a magnetostriction constant can be reduced while maintaining soft magnetic properties such as resistivity and magnetic permeability, and to provide thin film magnetic heads, planar magnetic elements, and filters using the soft magnetic films.
In accordance with the present invention, a soft magnetic film contains Fe as a major constituent, at least one element M selected from the group consisting of Zr, Hf, V, Nb, Ta, W, Mo, and rare earth elements (excluding Sm), at least one element L selected from the group consisting of Ti, Sn, Sm, and Si, and at least one element R selected from the group consisting of O, C, and N. The film has a structure which includes a mixture of an amorphous phase containing a large amount of the oxide of the element M and a fine crystalline phase containing a large amount of Fe, and the fine crystalline phase further contains the element L.
The fine crystalline phase is preferably composed of at least one structure selected from the group consisting of a body-centered cubic (bcc) structure, a hexagonal closest packed (hcp) structure, and a face-centered cubic (fcc) structure. More preferably, the fine crystalline phase is composed mainly of a bcc structure.
In the present invention, the fine crystalline phase has an average crystal grain size, preferably, of 30 nm or less, and more preferably, of 10 nm or less.
In accordance with the present invention, a soft magnetic film has a composition represented by the formula:
(Fe
1−a
Co
a
)
X
M
Y
L
Z
R
W
,
where the element M includes at least one element selected from the group consisting of Zr, Hf, V, Nb, Ta, W, Mo, and rare earth elements (excluding Sm), the element L includes at least one element selected from the group consisting of Ti, Sn, Sm, and Si, the element R includes at least one element selected from the group consisting of O, C, and N, the subscript a satisfies 0≦a≦0.1, and X, Y, Z, and W (in atomic percent) satisfy 45≦X≦70, 5≦Y≦30, 0.1≦Z≦10, and 10≦W≦40, respectively.
In the present invention, preferably, the element L includes at least one element selected from the group consisting of Ti, Sn, and Sm, and the subscript Z satisfies 0.1≦Z≦2.
In the present invention, preferably, the subscript W satisfies 30≦W≦40.
The soft magnetic film in the present invention may have a magnetostriction constant of 4×10
−6
or less in absolute value, a resistivity of 400 to 1,200 &mgr;&OHgr;·cm, and a magnetic permeability of 300 or more.
In accordance with the present invention, in a thin film magnetic head which includes a write head and/or a read head, at least one magnetic layer constituting the write head and the read head is composed of the soft magnetic film described above.
In accordance with the present invention, a planar magnetic element and a magnetic core of a filter are formed using the soft magnetic film.
REFERENCES:
patent: 5302469 (1994-04-01), Sugenoya et al.
patent: 5573863 (1996-11-01), Hayakawa et al.
patent: 5656101 (1997-08-01), Hayakawa et al.
patent: 5725685 (1998-03-01), Hayakawa et al.
patent: 2-199027 (1990-08-01), None
patent: 6-316748 (1994-11-01), None
patent: 10-55916 (1998-02-01), None
Hatanai Takashi
Makino Akihiro
Nakazawa Makoto
Sasaki Yoshito
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Pianalto Bernard
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