1. Field of the Invention
The present invention relates to a recording/reproducing head and a recording/reproducing apparatus incorporating the recording/reproducing head. More particularly, the present invention relates to a recording/reproducing head, a recording/reproducing apparatus, and a fabrication method thereof which are capable of higher-density recording than conventional hard disks and magneto-optical disk apparatuses.
2. Description of the Related Art
A hard disk drive (HDD) 1000 represented in FIG. 11 or a magneto-optical disk (MO) apparatus 2000 represented in FIG. 12 can record information signal in high density. These apparatuses include a magnetic head 1019 and a magneto-optical head 2020, respectively, as a recording/reproducing head.
When the magnetic head 1019 as shown in FIG. 11 is used to attempt to obtain high-density recording/reproducing which exceeds about 40 Gb/inch2, reproducing is feasible if a giant magnetoresistive (GMR) device 1014 is provided between shields 1015. In a structure of the magnetic head 1019 in which a surface of the GMR device 1014 is exposed, friction or noise occurs due to the GMR device 1014. When a tunnel type GMR (TMR) device is used instead of the GMR device 1014, a short circuit is likely to occur. Such a problem may be avoided by means of a so-called yoke-type head (not shown). In a conventional yoke-type head, however, a gap needs to be provided between the GMR device 1014 (or the TMR device) and the yoke, e.g., an insulating film or the like is provided in the gap. Such a gap, however, leads to a reduction in reproduced output. As to the recording, the width of a track needs to be on the order of less than a micron (<0.3 μm) while the film thickness of the magnetic head 1019 is held on the order of microns. This leads to an extraordinarily large aspect ratio and thus difficulty in processing. In the future, the length of a recorded bit in a recording medium is expected to be about 50 nm or less. In a recording medium having such a small bit size, thermal fluctuation must be taken into consideration. When an in-plane recording medium is used as a recording medium 1016, the coercive force of the recording medium 1016 needs to be significantly large. A recording magnet 1017 of the magnetic head 1019 is required to include a magnetic film having a saturated magnetization of about 2.5 T (tesla) or more so as to magnetize such a recording medium. At the present time, there exists substantially no such magnetic film.
On the other hand, in the magneto-optical head 2020 shown in FIG. 12, a recording medium 2016 is heated by laser light condensed by a condenser 2018 up to a temperature such that reversal of magnetization is likely to occur. In addition, a magnetization modulation technique using a magnetic head 2019 is utilized to record information into a bit which is smaller than the wavelength of laser light.
The magneto-optical head 2020 having the above-described structure shown in FIG. 12 can provide the same level of high-density recording as that of the HDD. Upon reproducing, however, the recorded bit needs to be enlarged up to as much as the wavelength of laser light. To this end, various methods have been proposed, but there still remains challenges insofar as practical use.
In such situations, a new recording/reproducing apparatus 3000 as shown in FIG. 13 has been proposed. The recording/reproducing apparatus 3000 includes a magneto-optical head 2020 and a GMR head 3019. Recording is performed using the magneto-optical head 2020. Reproducing is performed using the GMR head 3019. That is, two different heads are used for recording and reproducing, respectively. A recording medium 2016 for a magneto-optical disk is used as a recording medium.
On the other hand, in a recording/reproducing apparatus 4000 shown in FIG. 14, a magnetic head 1019 for HDD is used. A recording medium 4016 is irradiated by laser light at a side thereof opposite to the magnetic head 1019. This allows facilitation of reversal of magnetization in recording and facilitation of reading in reproducing.
However, the recording/reproducing apparatus 3000 shown in FIG. 13 requires two heads for recording and reproducing. There is a problem in that recording and reproducing are performed by the separate heads. Moreover, the recording/reproducing apparatus 4000 shown in FIG. 14 requires a servo technique to bring laser light to a region recorded on a recording medium. There is a problem in that the higher the density of recording, the greater the technical difficulty. In this case, there is also a significant problem with the processing of the small-width track in the HDD recording head as described above. In both the recording/reproducing apparatuses 3000 and 4000, the magnetic head and the laser irradiating section need to be provided on the upper and lower sides of the recording medium, respectively. For that reason, it is impossible to provide heads on the upper and lower sides of a disk and utilize both sides of the disk as recording surfaces. In terms of space-saving, such a structure is disadvantageous to the recording/reproducing apparatus.
Further, the magnetic head needs to be moved to a target position on a recording medium for recording or reproducing. In addition to the above-described problems, the higher the density of recording, the greater the difficulty in servo tracking when only one magnetic head driving section is provided in a conventional recording/reproducing apparatus.