Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2001-09-21
2004-12-07
Resan, Stevan A. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S611000, C428S668000, C428S681000
Reexamination Certificate
active
06828046
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a magnetic material usable in an inductive head performing a magnetic recording to such a magnetic recording medium as a hard disk, and, more particularly, to a soft magnetic film having not only a high saturation flux density but also a good soft magnetism and an anisotropic magnetic field, as well as a good thermal stability and a corrosion resistivity.
2. Description of the Related Art
As a magnetic recording medium has been provided with a higher recording density, a coercive force in a magnetic layer in the medium has been increasing. Therefore, a magnetic material of a recording inductive head used in a magnetic disk device is required to have a high saturation flux density so as to enhance a magnetic field for writing information (writing magnetic field). Conventionally, a plated permalloy, such as Ni
80
Co
20
or Ni
45
Fe
55
, is widely used as a magnetic pole of the inductive head, and a saturation flux density Bs of the permalloy is approximately 1-1.6T (tesla).
Additionally, Japanese Laid-Open Patent Application No. 11-74122 (Japanese Patent No. 2821456) proposes a material for a magnetic pole by enhancing the saturation flux density Bs close to 2T in CoNiFe. Henceforth, however, a recording density is surely to be made still higher, thus it is expected that there will be still increasing needs for a magnetic-pole material having a even higher saturation flux density Bs.
By the way, iron-cobalt (Fe—Co) alloys are generally known as materials having a high saturation flux density Bs. However, it is extremely difficult to achieve a soft magnetism with a composition that has a saturation flux density Bs exceeding 2T. For example, Japanese Laid-Open Patent Application No. 11-121232 discloses a technology which achieves soft magnetism in a state in which a microcrystalline phase comprising Co and other ferromagnetic 3d transition metals (Fe, Ni) exists in an amorphous phase composed mainly of various metallic elements (M) and oxygen (O).
This technology sets forth that equal to or more than 20 at % of nonmagnetic elements (the above-mentioned metallic elements (M) and oxygen (O)) need to be added so as to generate an amorphous phase to a certain extent. Conversely, however, in order to realize a saturation flux density Bs equal to or more than 2T, the addition of nonmagnetic elements needs to be restrained as much as possible.
Thus, it is extremely difficult to realize a soft magnetic material having a high saturation flux density Bs equal to or more than 2T.
Additionally, Japanese Laid-Open Patent Application No.9-115729 reports a soft magnetic material comprising a ceramic phase and a ferromagnetic hyperfine microcrystalline phase. However, it is also difficult to achieve a high saturation flux density Bs because the soft magnetic material that comprises the ceramic phase has a small magnetic moment.
Further, page 691 of the Journal of the Magnetics Society of Japan, vol. 24 (2000), discusses a Fe—Co—Al—O film manufactured by applying a magnetic field in the formation thereof. According to this journal, with a composition having a sparse proportion of nonmagnetic elements of aluminum (Al) and oxygen (O) which are restricted to 10 at % and 12 at %, respectively, an anisotropic magnetic field Hk becomes zero so as to make it difficult to obtain a uniaxial magnetic anisotropy.
Further in addition, Japanese Laid-Open Patent Application No. 10-270246 reports on a soft magnetic film having an anisotropic magnetic field (Hk>20 Oe), a resistivity (p>50 &mgr;&OHgr;cm), and a saturation flux density (Bs>1.6T). However, in order to enhance the resistivity equal to or more than 50 &mgr;&OHgr;cm, the content of nonmagnetic elements other than magnetic elements needs to be increased. Consequently, the saturation flux density Bs decreases, as described above; thus, it is difficult to achieve a high saturation flux density Bs exceeding 2T. Further, a moderate anisotropic magnetic field Hk cannot be obtained, either.
As heretofore described, it is extremely difficult to form a soft magnetic film having not only a high saturation flux density Bs as well as a high resistivity, but also an appropriate soft magnetism and a moderate anisotropic magnetic field Hk.
These strict conditions imposed on a soft magnetic film are a reflection of strict conditions imposed on a magnetic head used for recording. In other words, as a magnetic disk device is provided with a higher recording density, a magnetic recording head is required to have magnetic properties as described above.
A soft magnetic film is required to have a high saturation flux density Bs, as described above, so as to intensify a writing magnetic field to write to a magnetic recording medium, in accordance with a highly dense recording.
Additionally, this soft magnetic film is often formed as a magnetic yoke functioning as a magnetic path that leads a writing magnetic field generated by coils to a recording medium. This magnetic yoke is required to have a high resistivity. Accordingly, the soft magnetic film is required to have a high resistivity as a further condition.
However, in accordance with a recent remarkable increase in recording density, the width of an end portion of the yoke as a magnetic pole has been becoming submicron. With this shape in which the width of the end portion of the magnetic pole is equal to or thinner than the thickness of the outer layer, a loss due to an overcurrent becomes, an amount that can be ignored. Therefore, the resistivity does not have to be enhanced very much at the end portion for the yoke; rather, a saturation flux density Bs should be increased in the first place.
It is noted that, when the resistivity becomes low at the end portion of the yoke, a design change is possible so as to secure a high resistivity in the yoke as a whole.
Further, the recording inductive head is often formed as a complex magnetic head arranged with a reproducing head used for reading. A soft magnetic film used for recording in this complex magnetic head requires further considerations with respect to influences of temperatures in an annealing process in manufacturing steps thereof, in addition to the above-mentioned conditions.
Specifically, in forming the soft magnetic film used in the inductive head, considerations have to be made so as not to deteriorate properties of a magnetoresistive element used in the reproducing head. It is pointed out in general that, in forming the soft magnetic film used in the inductive head, annealing the soft magnetic film at a temperature exceeding 300° C. deteriorates the magnetoresistive element of the reproducing head.
For that reason, it is preferred that the soft magnetic film used in the inductive head has a soft magnetism at the formation thereof, and is thermally stable under approximately 300° C., or that the soft magnetic film has magnetic characteristics such that the soft magnetism is improved by being annealed at 300° C. or lower.
Therefore, a soft magnetic film disclosed in Japanese Laid-Open Patent Application No. 5-148595 is inappropriate as a magnetic-pole material used in a writing (inductive) head combined with a GMR reading (reproducing) head, because the soft magnetic material is annealed at 500-700° C. to improve a soft magnetism thereof, as a result of which a reading property thereof is deteriorated.
Additionally, a thin-film material used therein is composed of elements analogous with the elements mentioned in Japanese Laid-Open Patent Application No. 11-121232, in which a ferromagnetic microcrystalline phase and a surrounding amorphous phase inferably form a crystal structure. A conceivable reason why the soft magnetism is improved at high temperatures of 500-700° C. as mentioned above is that a structural relaxation and a phase change do not occur unless an activation energy corresponding to these temperatures is applied to a metastable phase comprising the ferromagnetic microcrystalline phase and the amorphous phase.
As heretofore described, there ar
Ikeda Shoji
Ohtsuka Yoshinori
Tagawa Ikuya
Uehara Yuji
Fujitsu Limited
Greer Burns & Crain Ltd.
Resan Stevan A.
LandOfFree
Soft magnetic film of FeCoMO having a high saturation flux... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Soft magnetic film of FeCoMO having a high saturation flux..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Soft magnetic film of FeCoMO having a high saturation flux... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3289509