Patent Application
20050128885
The present invention relates to a recording medium adopted for use in magnetic optical recording systems and particularly to a high-density thermal recording and magnetic reading recording medium that combines near-field optical recording and the reading technique of a sensitive magneto-resistive head.
How to increase the recording density of the recording media has always been an important issue in the field of recording media. The recording media, depending on different storing principles, may be divided into optical recording media and magnetic recording media. The optical recording media is restricted by optical diffraction limitation, while the magnetic recording media is restricted by super paramagnetic limitation, thus the recording density is difficult to increase as desired.
In recent years near-field optical and super resolution optical techniques have been adopted on optical disks to overcome the diffraction limitation of optical disk recording media. In the near-field optical techniques, a solid immersion lens (SIL) may be used to obtain an optical spot smaller than the diffraction limit, thereby a smaller recording bit may be formed to increase the recording density of the optical disk. However, the sliding distance between the objective lens and the disk has to be smaller than the wavelength of the laser light to generate a near-field effect. It makes design of the optical disk drive system more difficult. For instance, U.S. Pat. No. 6,614,742 discloses a technique that uses a solid immersion lens (SIL) for near-field recording. The SIL optical head requires a complex slider. Moreover, the distance between the optical head and the disk has to be maintained about 100 nm. This is very difficult in practical applications.
Guerra et al proposes an Integral Near-field Optical (INFO) technique, which directly uses a sub-micro cylindrical SIL on the substrate of the conventional DVD disk. It greatly shrinks the dimension of the optical spot and can increase the recording density of the optical disk. And the distance between the optical head and the optical disk does not need to be shrunk smaller than the wavelength of the laser light. It can resolve the hitting and scraping problem between the optical head and the optical disk during rotation of the optical disk caused by a too short distance there between in the near-field optical system. The recording density of the DVD disk may increase from 4.7 GB to 9.4 GB. (J. Guerra, D. Vezenov, P. Sullivan, W. Haimberger, and L. Thulin, “Near-field optical recording without low flying: integral near-field optical media”, Jpn. J. Appl. Phys. Vol. 41, pp.1866-1875, 2002). However, when this technique is adopted on the conventional magnetic optical disk, although the recording bit may be greatly shrunk, the operation of reading signals of the magnetic optical records is accomplished by detecting the Kerr angle of the reflection light. The Kerr effect diminishes with the shrinking of the detection area. Hence, when the magnetic area of the disk record is very small, namely the recording density is very high, the reflection light becomes weak and the signals might become not readable. It is not convenient in applications.
On the other hand, on the magnetic recording media, in order to increase the recording density, Hideki et al proposed a new thermal-magnetic recording and flux detection method in 1998 that combines the advantages of the magnetic optical disk which may form a clear vertical magnetic zone and the highly sensitive giant magneto-resistive head (GMR head) (H. Saga, H. Nemoto, H. Sukeda, and M. Takahashi, “New recording method combining thermo-magnetic recording and flux dection”, Jpn. J. Appl. Phys. Vol. 38, pp.1839-1840, 1999). The recording film is a conventional magnetic optical material. It uses the conventional thermal-magnetic recording method to record signals. It uses the GMR head to measure the magnetic flux to read signals. But the conventional magnetic optical materials are not suitable recording media for thermal recording and magnetic reading. This because the saturation magnetization (Ms) at room temperature is too small and cannot provide a sufficient magnetic flux for the GMR head to read signals.
In order to resolve the problems set forth above, the invention provides a high density thermal recording and magnetic reading recording medium and system that reduces the weight of the slider of the pickup head and simplifies the design thereof, and can greatly increase the recording density of the disk.
The high density thermal recording and magnetic reading recording medium and system according to the invention combines INFO recording and the sensitive reading technique of magneto-resistance head to overcome the limitation of optical diffraction to increase the density of recording media. The system includes a near-field optical laser, magneto-resistive head and a recording medium. The recording medium has a sub-micro cylindrical SIL so that when the near-field optical laser writes, an optical effect is generated to shrink the optical spot, and the recording medium can have a smaller recording bit to increase the recording density. Thereby the near-field optical laser can achieve the near-field optical recording effect without being close to the recording medium. As a result, the hitting and scraping problem that might otherwise occur, because to the laser is too close to the recording medium, may be avoided. Coupled with the magneto-resistive head to read data, the weight of the slider can be reduced and the design of the slider can be simplified.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.
Referring to
On the other hand, a magneto-resistive head 40 is used to read the data on the recording layer 11. It does not require a specially designed slider 21 to perform reading. Thus the weight of the slider (not shown in the drawings) can be reduced. The magneto-resistive head 40 can be a GMR head or Tunneling Magneto-resistance head (TMR head). A TMR head is preferred. The recording layer 11 is a magnetic recording film, which has a high saturation magnetization (Ms) and high vertical film surface coercive force (Hc) at room temperature. When the temperature rises, the vertical film surface coercive force drops rapidly to facilitate thermal-magnetic recording.
For recording data, the laser head 31 emits the laser light 311 which passes through a converging lens 32 and the substrate 12 to generate a near-field optical effect through the sub-micro cylindrical lenses 13, so that the recording layer 11 is magnetized. The magnetized direction is preferably normal to the surface (indicated by arrows in the drawing). Thereby, the recording density may increase. For reading, the magneto-resistive head 20 reads from one side of the recording layer 11. Thus the weight of the slider can be reduced and the design of the slider 21 can be simplified.
Refer to
While the preferred embodiments of the invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments, which do not depart from the spirit and scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 92135604 | Dec 2003 | TW | national |
