Dynamic magnetic information storage or retrieval – General recording or reproducing – Thermomagnetic recording or transducers
Patent
1985-05-06
1986-12-30
Canney, Vincent P.
Dynamic magnetic information storage or retrieval
General recording or reproducing
Thermomagnetic recording or transducers
360114, 369100, G11B 502, G11B 5127, G11B 700
Patent
active
046333380
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to a magneto-optical recording and reproducing apparatus having a magnetization direction detecting apparatus of a magnetic recording medium for detecting a magnetization direction of a magnetic recording medium, particularly a magnetic recording medium having a perpendicular magnetization layer on which a recording is carried out in a perpendicular magnetic recording mode or magneto-optical recording mode.
2. Background Art
The recording on a magneto-optical recording medium having a perpendicular magnetization layer, for example, magneto-optical disc is carried out by irradiating the perpendicular magnetization layer with a laser light beam which is modulated in intensity by a recording information signal. In the magneto-optical disc, during the non-recording mode, as shown in FIGS. 1A and 1B, a perpendicular magnetization layer 2 formed on a base plate 1 such as glass plate, acrylic plate and so on is thoroughly magnetized in the direction normal to the layer surface, or in the upward direction shown by arrows in FIG. 1A or in the downward direction shown by arrows in FIG. 1B. As shown in FIG. 2 the beam spot of a laser light L.B is incident on, for example, the magneto-optical disc magnetized upward shown in FIG. 1A to thereby form a cylindrical magnetic domain or a magnetic bubble domain with inverted magnetization in the portion irradiated with the beam spot and, thus the information is recorded. In this case, in order to positively form a magnetic bubble with inverted magnetization, the magneto-optical recording medium has applied to it an auxiliary bias magnetic field H.sub.W of about 500 Oe in the direction opposite to the magnetization direction in the non-recording mode. On the other hand, when an information is rewritten in the magnetization layer 2 on which the recording is carried out as described above and hence a magnetic bubble 3 is formed, if the magnetic bubble 3 shown in FIG. 2 is erased, an erasing magnetic field H.sub.E of about 700 Oe to 1000 Oe in the same direction as the magnetization direction during the non-recording mode is applied to the magnetization layer 2 and the laser light L.B is irradiated thereon so as to return the inverted magnetization direction of the magnetic bubble 3 to the original layer direction, and thus the magnetic bubble is erased.
As described above, when the information is recorded on and erased from the magneto-optical recording medium, for example, a magneto-optical disc, the directions of the external magnetic field H.sub.W and H.sub.E must correlate with the magnetization direction of the magnetic layer 2 so that it is preferable to detect the magnetization direction of the magnetization layer 2 prior to recording.
The magnetic recording medium of this kind is often formed such that the recording layer, i.e., the perpendicular magnetization layer is formed on both surfaces thereof so as to double the recording density. In this case, as shown in FIG. 4, since the perpendicular magnetization layers of both surfaces are magnetized in the same direction at the same time in a common magnetic field, it is preferable to determine the direction of the auxiliary biasing magnetic field H.sub.W or the erasing magnetic field H.sub.E in accordance with the recording on the front or back surfaces. In other words, it is preferable to select the direction of the magnetic fields H.sub.W and H.sub.E by detecting the front and back surfaces of the perpendicular magnetization layer.
This invention provides a magneto-optical recording and reproducing apparatus having a magnetization direction detecting apparatus of the magnetic recording medium capable of easily and positively detecting the magnetization direction of the perpendicular magnetization layer on the front and back surfaces of the magnetic recording medium having the above-described magnetization layer.
DISCLOSURE OF INVENTION
In this invention, as shown in FIG. 5, on the perpendicular magnetized layer of the magnetic recording medium such as a magneto-
REFERENCES:
patent: 4472748 (1984-09-01), Karo et al.
patent: 4495530 (1985-01-01), Yanagida
patent: 4558440 (1985-12-01), Tomitz
Sato Noboru
Watanabe Kenjirou
Canney Vincent P.
Sony Corporation
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