The heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The volume of information processing in the information age is increasing rapidly. In particular, HDDs have been desired to store more information in its limited area and volume. A technical approach to this desire is to increase the capacity by increasing the recording density of the HDD. To achieve higher recording density, further miniaturization of recording bits is effective, which in turn typically requires the design of smaller and smaller components.
The further miniaturization of the various components, however, presents its own set of challenges and obstacles.
As described above, a magnetic disk drive uses a magnetic head to record and play back the information on a magnetic disk (magnetic recording medium). As the magnetic spacing becomes smaller, the magnetic head and the magnetic disk can be closer, and information can be recorded in microscopic regions, and the minute magnetic signals on the magnetic disk can be played back. When the head-disk spacing narrows, the film thicknesses of the overcoats of the magnetic disk and the magnetic head must be reduced.
However, in order to prevent corrosion of the metals used in the recording layer of the magnetic disk and the recording and playback element of the magnetic head, the overcoat must be chemically stable, dense, and uniform. In addition, when the magnetic head is extremely close to the magnetic disk, sufficiently high resistance to abrasion must be present because of the relative rotational motions. Moreover, generally, as conventional overcoats of the magnetic disk and the magnetic head become thinner, the corrosion resistance degrades because the coverage decreases; the effective hardness decreases; and the abrasion resistance degrades. Therefore, in order to achieve thinner overcoats for the magnetic disk and the magnetic head while maintaining corrosion resistance and abrasion resistance, the density and hardness of the overcoats of the magnetic disk and the magnetic head must be improved, and the degradation caused by the thinner film thickness must be corrected.
In order to improve the recording density, suppression of thermal demagnetization of the recording medium and maintenance of the write characteristics should be simultaneously satisfied. The bit diameter of the recording medium should also be on the order of nanobits in order to achieve a high recording density. However, the problem of thermal demagnetization arises as the bit diameter decreases.
Information recorded on the recording medium is lost as time elapses because of fluctuations in the thermal magnetization, which cause thermal demagnetization. To solve the problem of thermal demagnetization, the thermal stability of the magnetization may be improved by using a material having high magnetic anisotropy. However, when the magnetic anisotropy becomes too high, the magnetization of the recording medium cannot be reversed by the recording magnetic field from the magnetic head recording element, and consequently, the magnetic medium is no longer able to be written to.
Specifically, to improve the surface recording density, new technologies are indispensable to simultaneously achieve the suppression of thermal demagnetization and the maintenance of the writing characteristics to the recording medium. One proposed method for solving this problem is thermally assisted recording (TAR). In this technology, magnetic recording is conducted while the coercive force is decreased by temporarily and locally heating the recording medium. By using this technology, writing is possible even for a recording medium having high magnetic anisotropy. As a result, the suppression of thermal demagnetization and the maintenance of the characteristics of writing to the recording medium are satisfied simultaneously, and a dramatic increase in the surface recording density can be realized. Consequently, thermal resistance becomes necessary for the overcoats of the magnetic disk and the magnetic head.
In particular, the development of technologies for improving the thermal resistance of the head-disk interface (HDI) is essential in producing a practical TAR method. A conventional HDI is composed of a magnetic head overcoat, a magnetic disk overcoat, and a lubricant film, each of which plays a role in preventing corrosion and abrasion of the head and disk, and maintaining high reliability of the magnetic disk drive. However, the structural elements of the HDI have carbon as the primary component and are believed to be susceptible to heat compared to metals or ceramics. Therefore, in the high temperature environment of TAR, the HDI structural elements are typically deformed and/or degraded by heat. As a result, degradation and deformation are concerns in the reliability of the magnetic recording system.
Conventional diamond-like carbon (DLC) films have been used as the disk overcoats of the HDI structural elements. However, in a high temperature environment considering the application to TAR, the mechanical resistance and chemical resistance required as the distance between the head and disk narrows must also be thermally stable for desirable results. Therefore, a property of the desired DLC film is an overcoat having high film density, that is, enhanced sp3 bonding (e.g., a diamond structure).
However, DLC films produced by a conventional sputtering method have a structure close to that of graphite, thereby having few sp3 bonds. Moreover, a DLC film formed by chemical vapor deposition (CVD) includes hydrogen in the film because a hydrocarbon gas is used as a raw material, but it is difficult to achieve a high sp3 bonding ratio via this method.
As described above, in order to achieve a higher recording density in magnetic disk drives, the demands for the overcoats of the magnetic disk and the magnetic head are a thinner shape and higher thermal resistance. To ensure higher reliability as a magnetic disk drive, higher density, hardness, and higher thermal resistance are desirable.
Thus it would be beneficial to develop a system with high recording density by improving the corrosion resistance and abrasion resistance in order to produce thinner films. Moreover it may be beneficial to improve the heat resistance in order to improve the practicality of implementing TAR.