Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-06-30
2003-01-21
Rickman, Holly (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S690000, C428S697000, C428S690000, C428S900000, C360S097010, C360S131000, C360S135000
Reexamination Certificate
active
06509111
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is related to a magnetic recording media which is possible to record large volume information and to a magnetic disk apparatus using this media, particularly suitable to a magnetic recording media and a magnetic disk apparatus for high density magnetic recording.
The requirement for larger capacity to a magnetic disk apparatus is increasing more and more. There are some countermeasures in order to increase the recording density such as (1) improvement of the sensitivity of a reproducing part of a magnetic head, (2) narrower distance between a head element and a recording surface of a magnetic recording media and (3) higher efficiency of a signal processing.
The adoption of a composite magnetic head, which is separated into a recording part and a reproducing part and uses a highly sensitive element utilizing magneto-resistive effect as the reproducing part, is rapidly increased in these years. Recently, a magnetic head utilizing the effect of large variation of magneto-resistance (i.e., giant magneto-resistive effect, or spin valve effect) of a stacked type magnetic layer, which is a stack of plural magnetic layers with non-magnetic layers intervened, is in practical use for the purpose of more improvement of the sensitivity of reproducing part of a head. This utilizes the variation effect of magneto-resistance cased by a relative change of magnetizing direction of plural magnetic layers with non-magnetic layers intervened, forced by a leakage magnetic field from the magnetic recording media.
On the other hand, as important factors to higher recording density of a magnetic recording media, such are listed up as (1) lower noise of a recording media matching to an improved sensitivity of the reproducing part of a magnetic head, (2) more flatness of the surface roughness of a media accompanied by narrower spacing between a head element and the recording film of a magnetic recording media and (3) thinner protective layer.
A longitudinal magnetic recording media using alloy with Co as a main component such as CoNiCr, CoCrTa, CoCrPt, or CoCrPtTa is widely used as a magnetic layer of magnetic recording media. A magnetic layer of Co-alloy containing Pt, particularly, exhibits high coercivity and increases output at high linear recording density region, so that it is suitable for high recording density. These Co-alloys conform to hexagonal closed packed construction with c axis as easy axis of magnetization, so it is preferred that c axis is directed longitudinally for the application of longitudinal magnetic recording media. Therefore, there is widely used procedure that the under layer of body centered cubic construction is formed first on a substrate, then Co-alloy magnetic layer is formed on it by epitaxial growth, thus c axis is directed longitudinally.
Conventionally, Cr has been used as under layer. But in case that large atoms as Pt, etc. are contained in the magnetic layer, a method of making c axis orient crystallographically parallel to the film surface is proposed (JP-A-NO.63-197018, JP-A-No.62-257618) by improving lattice matching between magnetic layer and under layer, using Cr-alloy whose lattice space is increased by adding Ti (JP-A-No.63-197018) or V (JP-A-NO.62-257618) to Cr. As for under layer materials other than these, it is disclosed by JP-A-No.63-187416 that a wide variety of materials including Mo, W, Hf, and so on are usable. And as disclosed by JP-B-No.10-143865, it is shown that media noise can be stably decreased by forming amorphous alloy layer containing Cr or Zr of highly oxidization tendency, in addition to Co as the main component, between Cr-alloy under layer as described above and a substrate, and by slightly oxidizing the surface by exposing the surface in oxygen atmosphere.
The following is proposed as a technology to improve reliability against contact of magnetic head and magnetic recording media. That is, preferable surface structure of magnetic recording media is proposed by JP-B-No.5-114127 and JP-B-No.8-297834 concerning wear reliability, which is suitable to preventing head crash and media damage mainly occurred by CSS (Contact Start Stop) at starting or stopping of an apparatus. And the media surface is proposed by JP-B-No.11-232638 to prevent contact of head and media. JP-B-No.7-95369 proposes a method applying projection on the media surface in order to improve wear reliability of a flexible disk using a contact type head.
In addition, a method to retract a magnetic head out of the media at stopping of the media rotation is disclosed by JP-B-No.11-110933 in order to reduce the media surface roughness accompanied by narrower flying height of the head and prevent adhesive problem of a magnetic head at stopping at the same time.
It became possible by the above prior art to prevent from adhesive problem of a head on the magnetic media and to decrease media noise caused by higher playback sensitivity of the magnetic head. However, the spacing is getting narrower rapidly in these days to achieve higher recording density, so that the head and media interface is becoming difficult to prevent a head from contact with the media even during recording or reproducing operation. Therefore, it is required for media surface to minimize the spacing loss and besides realize high wear reliability.
SUMMARY OF THE INVENTION
The first purpose of the present invention is to present a high wear reliable magnetic media with low friction even under such a condition of low glide height as described above in conjunction with low noise characteristics which is important to achieve high recording density. The second purpose is to present a highly reliable and large capacity magnetic storage apparatus.
In order to solve the problem described above, various kinds of magnetic recording media were prepared, which were formed of a magnetic alloy layer containing Co as the major component on an under layer on a substrate, a protective layer containing C as the major component and a lubricant layer stacked in the order, by changing the structure of the under layer and the surface shape of the media and their characteristics were evaluated. As the result it was found that a good result was obtained and the first purpose described above was achieved when the under layer was formed of plural under layers including first layer of substantial amorphous and second layer of crystalloid laid in that order, and &Dgr;BH[0.01, 50] defined by |BH[0.01%]−BH[50%]|, which is the difference of the height of BH[0.01%] (i.e., Bearing ratio is 0.01%) and the height of BH[50%] (i.e., Bearing ratio is 50%), was not smaller than 3 nm and not larger than 6 nm in the Bearing Curve given by a surface roughness curve of the magnetic recording media.
By forming substantial amorphous layer as the first under layer, the second under layer of crystalloid formed on the first layer can be of fine crystalloid, and the crystalloid of the magnetic layer formed on it becomes also fine, so that the media noise is decreased. In addition, the growth of abnormally large particles of crystalloid, which are observed during the crystal growth in case of crystalline film, is suppressed by making the first layer be substantial amorphous. Thus, the probability of contact of the slider and the media is decreased when the glide height of a magnetic head slider is reduced, so that both of less media noise and higher reliability are achieved at the same time. The wording of ‘substantial amorphous’ herein defines the structure which diffraction pattern is observed as halo by a photograph of selected area electron diffraction image by a transmission electron microscope. The microscopic structure of layers constructing this kind of magnetic recording media can be evaluated by observing with a transmission electron microscope with high magnifying power, or by observing the diffraction ring pattern of selected area electron diffraction image, a sample piece thinly sliced in perpendicular direction to the surface
Endo Naoto
Goda Noriyoshi
Hosoe Yuzuru
Kato Akira
Shoda Mitsuhiro
Kenyon & Kenyon
Rickman Holly
LandOfFree
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