Magnetic film

Details Magnetic film Magnetic film

1999-09-02

2003-10-14

LaVilla, Michael (Department: 1775)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Physical dimension specified

C428S632000, C428S627000, C428S690000, C428S693100, C428S690000, C360S110000, C360S125330

Reexamination Certificate

active

06632520

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic film having a high saturated magnetic flux density used in a recording head and a magnetic reproducing head of a hard disk drive (HDD), a magnetic sensor such as a magnetic impedance sensor, and a magnetic circuit component such as a magnetic coil and an inductor; a method for producing the magnetic film; and a thin film head using the magnetic film.
2. Description of the Related Art
In recent years, the maximum recording frequency of HDDs has remarkably increased to about 200 MHz. Furthermore, high-density recording media are likely to have a high coercivity. Therefore, there has been a demand for a recording head material which has a high effective magnetic permeability even at a high frequency and in which a magnetic pole is unlikely to be saturated (i.e., a recording head material which has a high resistivity (high &rgr;), strong uniaxial anisotropy, and a high saturated magnetic flux density (high Bs)).
In order to satisfy the above-mentioned demand, F—N type material such as FeCrN (J. Appl. Phy. 81(8), Apr. 15, 1997) and FeRhN (IEEE Trans. Magn. VVOl 133. No. 5, 1997) formed by sputtering has been reported as a materiel, for example, with Bs of 2 T (tesla) or more.
The above-mentioned material with high Bs has a low resistivity; therefore, it is difficult to use such material at a high frequency. However, it has been reported that such material is used with a non-magnetic insulator (Al
2
O
3
, SiO
2
, etc.) so as to suppress an eddy current loss (The Japan Society of Applied Magnetics, document of The 103 th Research Institute, p. 2, 1998).
As shown in
FIG. 40
, U.S. Pat. Nos. 5,543,989 and 5,686,193 disclose a magnetic film with magnetic pole end regions
119
and
123
, including a layered structure of a seed layer of sendust and a bulk layer of sendust.
As material for a single layer with high &rgr;, Fe—M—O (M=Hf, Zr) (Summary of the lecture in the 122 nd Japan Society of Metal, p. 179 (424) 1998) is known; however, it has a disadvantage of low Bs. It is required that the above-mentioned material with high Bs or high &rgr; is capable of providing uniaxial anisotropy and suppressing a ferromagnetic resonance loss. For this purpose, heat treatment in a magnetic field or film formation in a magnetic field is conducted.
However, even in the case where uniaxial anisotropy is given to a conventional film with high Bs, a recording magnetic pole used in a thin film head has an increased aspect ratio between the thickness and the width of a magnetic pole due to a decreased width of a track. Therefore, magnetic anisotropy is caused by an anti-magnetic field in a direction perpendicular to the surface of a recording gap between an upper magnetic pole and a lower magnetic pole.
Because of the above, the direction of a magnetization easy axis shifts in the direction perpendicular to the film surface, which complicates a domain structure in the entire magnetic pole. As a result, magnetic characteristics at a high frequency degrade.
Furthermore, in the case where a magnetic pole is formed by a layered structure including a conventional layer with high Bs and an insulation resistant layer, it is required that at least two sources for supplying material are used for forming the layer with high Bs and the insulation resistant layer, and that these layers are alternately formed, which results in a longer period of time of film formation.
Furthermore, in performing a dry etching technique for minute processing (i.e., patterning of a magnetic pole), an etching rate of a magnetic material of transition metal such as Fe, Co, and Ni is substantially different from that of a non-magnetic insulating material such as Al
2
O
3
and SiO
2
. Thus, for example, in the case where radical etching or reactive ion etching (RIE) with a high etching rate is conducted, since these reactions are isotropic, unevenness is formed on cross-sections of the magnetic layer and the non-magnetic insulating layer. Furthermore, when reactive gas to be used for each layer is varied, a processing speed as a whole is decreased due to gas substitution, and a device becomes complicated.
Furthermore, in the case where the above-mentioned film is used in high-frequency recording, a spin valve film is used for a reproducing head. At least one of the magnetic layers included in the spin valve film is a fixed layer whose magnetization is fixed in a direction of medium magnetization, and the direction of fixed magnetization is orthogonal to the direction of uniaxial anisotropy required for a recording magnetic pole film for a high frequency.
The recording magnetic film which has been conventionally developed is produced while uniaxial anisotropy is obtained. Alternatively, after the recording magnetic film is produced, uniaxial anisotropy is formed by heat treatment in a magnetic field. Therefore, anisotropy of the recording magnetic film is weakened due to the heat treatment in a magnetic field conducted for fixing the fixed layer of the spin valve film in a preferable direction of the fixed magnetization.
Furthermore, when an upper magnetic pole is formed, the quality of a slope portion degrades due to oblique formation.
SUMMARY OF THE INVENTION
A magnetic film of the present invention includes a magnetic layer and an intermediate layer alternately formed, wherein the magnetic layer has a composition represented by (M
1
&agr;
1
X
1
&bgr;
1
)
100−
&dgr;
1
A
1
&dgr;
1
(where &agr;
1
, &bgr;
1
, and &dgr;
1
represent % by atomic weight; M
1
is at least one magnetic metal selected from the group consisting of Fe, Co, and Ni; X
1
is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Si, Ge, Sn, Al, Ga, and transition metals excluding the M
1
; and A
1
is at least one selected from the group consisting of O and N), the magnetic layer has the following composition range:
0.1≦&bgr;
1
≦12
&agr;
1
+&bgr;
1
=100
0<&dgr;
1
≦10
the intermediate layer has a composition represented by (M
2
&agr;
2
X
2
&bgr;
2
)
100−
&dgr;
2
A
2
&dgr;
2
(where &agr;
2
, &bgr;
2
, and &dgr;
2
represent % by atomic weight; M
2
is at least one magnetic metal selected from the group consisting of Fe, Co, and Ni; X
2
is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Si, Ge, Sn, Al, Ga, and transition metals excluding the M
1
; and A
2
is at least one selected from the group consisting of O and N), the intermediate layer has the following composition range:
0.1≦&bgr;
2
≦80
&agr;
2
+&bgr;
2
=100
&dgr;
1
≦&dgr;
2
≦67
In one embodiment of the present invention, the X
1
contains at least one selected from the group consisting of Si, Al, Ti, and V.
In another embodiment of the present invention, M
1
=M
2
and X
1
=X
2
.
In another embodiment of the present invention, A
2
contains O.
In another embodiment of the present invention, assuming that an average thickness of the magnetic layer is T
1
and an average thickness of the intermediate layer is T
2
, the following expressions are satisfied:
2 nm≦T
1
≦150 nm
0.4 nm≦T
2
≦15 nm
1≦T
1
/T
2
≦50
In another embodiment of the present invention, the magnetic film satisfies the following expressions:
20 nm<T
1
≦150 nm
1 nm<T
2
≦15 nm
4≦T
1
/T
2
≦50
at least 50% of magnetic crystal grains included in the adjacent magnetic layers via the intermediate layer spread across the intermediate layer.
A magnetic film of the present invention includes a magnetic layer and an intermediate layer alternately formed, wherein the magnetic layer has a composition represented by (M
1
&agr;
1
X
1
&bgr;
1
)
100−
&dgr;
1
A
1
&dgr;
1
(where &agr;
1
, &bgr;
1
, and &dgr;
1
represent % by atomic weight, M
1
is at least one magnetic metal selected from the group consisting of Fe, Co, and Ni; X
1
is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Si, Ge, Al, Ga, and transition metals including a IVa group, a Va group, and Cr; and Al is at least one selected from t

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