Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
1998-12-08
2001-04-24
Pianalto, Bernard (Department: 1762)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C427S131000, C427S132000, C428S336000, C428S639000, C428S640000, C428S641000, C428S662000, C428S663000, C428S669000, C428S680000, C428S693100, C428S690000, C428S690000, C428S690000, C428S900000, C428S928000
Reexamination Certificate
active
06221508
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to magnetic storage apparatus and, more particularly, to high-density magnetic storage devices having the recording density of more than 4 gigabits per square inch (Gbit/in
2
). The invention also relates to magnetic recording media of low noise and high reliability with reduced reproduction output attenuation occurring due to thermomagnetic relaxation to attain high-density recordabilities required.
In recent years, as magnetic storage apparatus rapidly increases in recording density, it is demanded to attain high-sensitivity magnetic heads along with advanced magnetic storage media high in magnetic coercive force and yet low in noise. While currently available magnetic head assemblies typically employ a magnetic head of the magnetoresistance effect type, also known as magnetoresistive (MR) heads, an endless demand for increased data storage density calls for accelerated development of further advanced magnetic heads of the giant magnetoresistance (GMR) type which are two or three times greater in sensitivity than standard MR heads.
In addition, as portable or handheld personal computers (PCs) such as “notebook” PCs are sharing larger part in the digital computer market, prior known storage media with an Al—Mg alloy substrate metallized or plated with NiP (referred to as “Al substrate” hereinafter) are being replaced with glass-substrate media having enhanced physical durability or robustness against attendant shocks during hand-carrying or “on-the-fly” usage outside the users' offices, which media are under accelerated development today. Unfortunately, advantages of such glass-substrate media do not come without accompanying a penalty: these tend to decrease in magnetic properties more significantly than conventional Al-substrate media due to defective adherence, immersion or “invasion” of impurity gasses from a substrate into its associative films, degradation of in-plane orientation of magnetization easy axis, increased particle or grain sizes, and others. An approach to avoiding such problem associated with the prior art is to newly form between the substrate and an undercoat layer or underlayer more than one additive layer including an intermediate layer, seed layer, barrier layer and the like. One typical scheme incorporating this principle has been disclosed in, for example, JP-A-1-134913 (laid open on May 26, 1989). A similar scheme is set forth in JP-A-1-134984 (laid open on May 26, 1989). These Japanese documents teach and suggest that the adhesiveness might increase by formation of an intermediate layer which is made of oxide of a chosen metal containing therein at least one element as selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and Mn, which leads to achievability of good contact-start-stop (CSS) characteristics. In addition, referring to JP-A-4-153910 (laid open on May 27, 1992), it is disclosed therein that formation of an amorphous or micro-crystalline film may enable miniaturization of particle or grain dimensions to thereby reduce the risk of attendant noises, which film is comprised of Y as well as one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. JP-A-5-135343 (laid open on Jun. 1, 1993) demonstrates the fact that forming on a glass substrate an oxygen isolator layer allows resultant magnetic coercive force to increase, which layer contains therein a chosen rare earth element in addition to one kind of element selected from the group consisting of Ta, Y, Nb and Hf. Reference is further made to JP-A-7-73441 (laid open on Mar. 17, 1995), which indicates obtainability of higher coercive force by forming on a substrate either an amorphous Cr alloy or V alloy because such formation permits a Cr under-layer formed thereon to exhibit the (211) orientation causing a Co-alloy magnetic layer to have the (10.0) orientation with its magnetization easy axis facing the inside of a film surface, i.e. lying parallel to the film surface.
SUMMARY OF THE INVENTION
A layer as directly formed on a substrate for purposes of grain size control and impurity invasion elimination and so on will consistently be referred to as the first underlayer, whereas another underlayer with the body-centered cubic (“bcc”) structure made of a Cr alloy or any equivalents thereto for orientation control of a magnetic epitaxial-growth layer will be as the second underlayer in the description below.
Also note that while medium noise reduction calls for miniaturization or microfabrication of magnetic particle or grain diameters along with reduction of interaction between grains for interchanging, resultant recording magnetization can decrease or attenuate with time due to the fact that miniaturized or “shrank” magnetic crystals would be affectable from thermal disturbance more significantly. This is called the “thermomagnetic relaxation,” which will become significant with an increase in recording density. In light of the foregoing, in order to achieve ultrahigh recording density, it should be required to suppress or minimize any possible thermomagnetic relaxation while at the same time letting noise reduction be obtainable.
It is therefore an object of the present invention to provide an improved magnetic storage apparatus and a magnetic recording medium adaptable for use therewith.
It is another object of the invention to provide a high-density magnetic recording medium of low noise with enhanced stability against thermomagnetic relaxation as achievable through appropriate control of the crystal orientation and average grain dimension as well as grain size distribution in more than one magnetic layer used therein.
It is a further object of the invention to provide a magnetic storage apparatus high in reliability having an increased recording density of more than 4 gigabits per square inch as attainable by use of a high-sensitivity magnetic head in combination with the magnetic recording medium.
In accordance with one aspect of the instant invention, a magnetic storage apparatus is provided which includes: a magnetic recording medium having a magnetic layer formed on a substrate with a single or multiple underlayers laid between them and featured in that at least one of the underlayers is made of an amorphous or microcrystalline material which contains therein Ni as its main component and also contains at least one kind of element selected from the group consisting of Nb and Ta; a drive unit for driving the record medium in the recording direction; a magnetic head assembly consisting essentially of a recorder section and reproduction section; means for forcing the magnetic head assembly to relatively move with respect to the magnetic record medium; and, record/playback signal processor means for handling signal inputting toward the magnetic head and for performing reproduction of an output signal from the magnetic head, wherein the reproduction section of said magnetic head is configured from a magnetoresistive (MR) head.
In accordance with another aspect of the invention, a magnetic storage apparatus is provided including: a magnetic recording medium having a magnetic layer formed on a substrate with a single or multiple underlayers sandwiched therebetween, at least one of which layers is comprised of an amorphous or micro-crystalline material containing as its principal component at least one kind of element selected from the group consisting of Nb, Zr, Ta, and Mo and also containing Si therein; a drive unit for driving the record medium in the recording direction; a magnetic head assembly formed from a recorder section and reproduction section; means for forcing the magnetic head assembly to move relative to the magnetic record medium; and record/playback signal processor means for handling signal inputting to the magnetic head and for performing reproduction of an output signal from the magnetic head, wherein the reproduction section of said magnetic head is structured from an MR head.
Use of an amorphous or microcrystalline material containing Si mentioned a
Hosoe Yuzuru
Kanbe Tetsuya
Kirino Fumiyoshi
Koiso Nagatugu
Matsunuma Satoshi
Hitachi , Ltd.
Kenyon & Kenyon
Pianalto Bernard
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