The present invention relates to a magnetic head slider and a magnetic disk device using the same, and more particularly, it relates to a magnetic head slider which is suitable for use in combination with a continuous medium type disk and a magnetic disk device using the same.
In the field of magnetic disk devices using a floating type magnetic head, it is required to record and reproduce data on and from a disk with a high density and at a high speed in response to recent requirements for increases in the amount of data processing. For this reason, the floating height of the magnetic head is increasingly reduced and it is expected in the future that magnetic reading and writing of data on a disk will be performed without a gap, while the magnetic head is sliding on the disk. Depending on these objectives, development of materials for both the magnetic disk and the magnetic slider which exhibit a small wear amount is highly demanded, and many materials for both the magnetic disk and the magnetic slider which exhibit a small wear amount already have been proposed.
For example, with a view toward reducing mechanical shaving off or abrasive wear during solid-solid contact between a magnetic head slider and magnetic disk, JP-A-1-258219(1989) proposes matching the hardness between a surface protective film of the magnetic disk and the magnetic head slider within .+-.10%, and from a view point of reducing the friction coefficient, JP-A-63-269384(1988) and JP-A-1-137483(1989) propose formation of several kinds of lubricants in solid and liquid form on the floating surface of the magnetic head slider and adhering methods thereof.
In addition to the above requirement of improving the slidability of the magnetic head slider, the magnetic head slider has to fulfill many required characteristics as a structural material. For example, in a composite type magnetic head, materials such as barium titanate (BaTiO.sub.3) and calcium titanate (CaTiO.sub.3), which show comparatively large thermal expansion coefficients, are among ceramics materials that are used because of the necessity for matching the thermal expansion coefficient with the magnetic head element. Many proposals for improving the sintering property of these sinter bodies have been proposed, such as in JP-B-52-30162(1977), JP-B-51-42606(1976), JP-B-51-15528 (1976), JP-A-2-88458 (1990), JP-A-2-80365(1990), JP-A-2-124762(1990).
Further, for the purpose of improving the slidability in the conventionally and generally used material Al.sub.2 O.sub.3 --TiC, an addition of TiO.sub.2 into Al.sub.2 O.sub.3 is suggested in JP-A-57-198578(1982).
However, even with the above indicated conventional measures, it was still difficult to reduce the wear amount over a long time span.
With regard to the above proposal of matching the hardness of the surface protective film for the magnetic disk and the magnetic head slider, such a measure is effective for reducing shaving off abrasive wear; however, the wear is also caused by third bodies, such as by wear powders of the slider itself, produced during the initial wear stage, and therefore the wear can not necessarily be controlled by hardness matching alone. Further, for magnetic disks having a carbon protective film on the surface thereof, it is noted that the carbon protective film produces oxidized wear powders due to the heat of friction, and for this mere reason, it is impossible to propose low wear materials simply based on hardness matching.
With regard to the above proposal of forming a lubricant on the floating face of the magnetic head slider, the friction coefficient is indeed reduced by this technique; however, the process of forming the lubricant layer is added step, and further, it is sometimes difficult to maintain the lubricity for a long time span, so that there is a tendency to solve the problem of the friction coefficient on the basis of the property of the material itself.
Materials combined with such materials as barium titanate (BaTiO.sub.3) and calcium titanate (CaTiO.sub.3) developed for a composite type magnetic head slider are primarily considered from the view point of their thermal expansion coefficients.
The present invention also uses TiO.sub.2 as its major component and includes somewhat similar compositions as the conventional ones; however, as a result of experiments on the sliding property of materials, it was found out that no improvement of the sliding property could be achieved with the addition of Ca and Ba. Further, although the slidability of the material is greatly affected by the amount of additives, the slidability can not be improved unless the amount of the TiO.sub.2 component exceeds 50 atm %; therefore, if the TiO.sub.2 component of less than 50 atm % is added to Al.sub.2 O.sub.3, the advantages achieved by the present invention can not be obtained.
USPTO Backgrounds
USPTO Backgrounds