Alloys or metallic compositions – Cobalt base
Reexamination Certificate
2000-10-05
2003-07-15
Rickman, Holly (Department: 1773)
Alloys or metallic compositions
Cobalt base
C420S436000, C420S439000, C420S440000, C420S581000, C420S585000, C420S586000
Reexamination Certificate
active
06592811
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a magnetic material having a high saturation magnetic flux density and a low coercive force and suited for use in a recording magnetic core, and a magnetic head having a magnetic core including the magnetic material.
(b) Description of a Related Art
A magnetic recording head for use in a magnetic data recording/reproducing device, such as a magnetic disk drive, is requested to generate a strong and steep writing magnetic field in order for high-density magnetic recording. For achieving a strong writing magnetic field, the magnetic materials for use in the recording magnetic core should have a higher saturation magnetic flux density. In addition, since the magnetic material should be excited by as low an exciting current flowing through a writing coil as possible, the magnetic material should have excellent soft magnetic properties such as a lower coercive force and a higher permeability.
The conventional magnetic materials used in the recording magnetic core include a nickel-iron alloy selected from the nickel-iron alloys called Permalloys, that includes nickel at about 82% and has a substantially zero magnetic distortion constant. This type of permalloys, which is called hereinafter “82 permalloy”, has a saturation magnetic flux density of about one tesla [T]. If it is possible to use a magnetic material having a saturation magnetic flux density higher than that of the 82 permalloy in a magnetic head, the resultant magnetic head generates a higher and steeper writing magnetic field.
Patent Publication JP-A-2-68906 describes a three-component plating magnetic film, or CoNiFe film. In the three-component plating CoNiFe film, the Ni content should be as low as possible in order to achieve a higher saturation magnetic flux density. To the contrary, however, the Ni content should be as high as possible in order to obtain a fcc structure which affords excellent soft magnetic properties, such as a low magnetic distortion. That is, the high saturation magnetic flux density and the excellent soft magnetic properties are trade-off in the three-component plating CoNiFe film.
On the other hand, Patent Publication JP-A-11-74122 describes another three-component plating CoNiFe film wherein the high saturation magnetic flux density and the excellent soft magnetic properties are compatible. In the plating CoNiFe film described in the latter publication, by conducting the filming without adding additives such as saccharin, a saturation magnetic flux density as high as 2.0 tesla or above is achieved even in the case of Ni content being around 10 weight percents (wt %).
FIGS. 1 and 2
show the boundary lines between the compositions for obtaining fcc structure and the bcc structure in the three-component plating CoNiFe film in the cases of no saccharin addition and saccharin addition, respectively. As understood from these drawings, the boundary line between the fcc structure and the bcc structure in the case of no saccharin addition is significantly shifted toward the lower side of the Ni content compared to the case of saccharin addition. This teaches that the crystal structure of the three-component plating CoNiFe film can be controlled based on the content of each component as well as the process conditions.
In short, the latter publication describes a magnetic material which achieves excellent soft magnetic properties as well as a high saturation magnetic flux density around 1.8 to 2.0 tesla by priorly orienting the magnetic material toward the fcc plane. The terms “fcc” and “bcc” as used herein mean the “face-centered cubic lattice” and the “body-centered cubic lattice”, respectively.
In order to achieve a magnetic recording operation for a magnetic disk having a recording capacity as high as 10 giga-bit or more, it is considered that the magnetic head should be able to write data to or read data from the magnetic disk having a coercive force of 4000 oersted or more. In this case, the recording magnetic head is also requested to achieve a steeper magnetic field gradient and a higher saturation magnetic flux density.
The magnetic head having the three-component plating CoNiFe film described in the latter publication does not have a sufficient recording ability on the recording medium having a coercive force of 4000 oersteds or more, so long as a NiFe film having a saturation magnetic flux density around 1 Tesla is used as an underlying layer for the CoNiFe film. In addition, a CoNiFe film, if used as an underlying layer for the three-component plating CoNiFe film, has problems in that a lower coercive force sufficient as a soft magnetic property is not obtained, and that the CoNiFe film is dissolved during the fabrication process due to a poor corrosion resistance.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a magnetic material having a higher corrosion resistance, a higher saturation magnetic flux density and excellent soft magnetic properties.
The present invention also provides a magnetic head having such a magnetic material.
The present invention also provides a magnetic head including a recording head including first and second magnetic cores sandwiching therebetween a recording gap, and a writing coil for generating a magnetic flux in the first and second magnetic cores and a writing magnetic field in the recording gap, the second magnetic core including a first magnetic layer made of a first magnetic material and a second magnetic layer formed on the first magnetic layer, the first magnetic material including a main component thereof expressed by a general formula CoNiFeX, wherein X is at least one element selected from the group consisting of Cr, Ti, V, Ru, Rh, Pd, Os, Ir and Pt, and wherein weight percentages a, b, c and d of Co, Ni, Fe and X contents, respectively, in said main component are such that 40%≦a≦75%, 5%≦b≦20%, 10%≦c≦30%, and 0%≦d≦10%.
In accordance with the magnetic material of the present invention, a higher saturation magnetic flux density, excellent soft magnetic properties and a high corrosion resistance can be achieved due to the specified composition thereof.
It is preferable that the magnetic material of the present invention has a peak intensity of the bcc (110) measured by X-ray diffraction which is 0.1 to 1.0 times the peak intensity of the fcc (111) measured by X-ray diffraction. In addition, a film made of the magnetic material may be formed on an orientation control film. The orientation control film may preferably include at least one substance selected from the group consisting of Ta, Zr, Ti, Mo, Cr, V and NiFe. The orientation control film may have a preferable thickness of 10 nm to 100 nm for further improving the characteristics of the magnetic material.
The present invention also provides a magnetic head including a recording head including first and second magnetic cores sandwiching therebetween a recording gap, and a writing coil for generating a magnetic flux in the first and second magnetic cores and a writing magnetic field in the recording gap, the second magnetic core including a first magnetic layer made of a first magnetic material and a second magnetic layer formed on the first magnetic layer, the first magnetic material including a main component thereof expressed by a general formula CoNiFeX, wherein X is at least one element selected from the group consisting of Cr, Ti, V, Ru, Rh, Pd, Os, Ir and Pt, and wherein weight percentages a, b, c and d of Co, Ni, Fe and X contents, respectively, in said main component are such that 40%≦a≦75%, 5%≦b≦20%, 10%≦c≦30%, and 0%≦d≦10%.
In a preferred embodiment of the present invention, the second magnetic recording layer can be formed as a plating layer for the underlying first magnetic recording layer. This structure affords a strong and steep magnetic field for the magnetic head.
The second magnetic recording layer may include a first film including CoNiFe as a main component thereof and a second film including NiF
Honjo Hiroaki
Ishi Tsutomu
Ishiwata Nobuyuki
Nonaka Yoshihiro
Saito Mikiko
NEC Corporation
Rickman Holly
Sughrue & Mion, PLLC
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