Dynamic magnetic information storage or retrieval – General recording or reproducing – Thermomagnetic recording or transducers
Patent
1992-03-17
1994-01-25
Nguyen, Hoa
Dynamic magnetic information storage or retrieval
General recording or reproducing
Thermomagnetic recording or transducers
369 13, 360114, 365122, G11B 1304, G11B 1112, G11B 1110
Patent
active
052820955
ABSTRACT:
A magneto-optical recording medium on which new information can be directly over-written over pre-existing recorded information. Such medium comprises two magneto-optical recording layers which have a difference in Curie temperature in the range of 0.degree. C. -25.degree. C. and which are separated from each other by a metal layer for the transfer of heat, such as aluminum. Recording is effected by scanning the medium with a write spot produced by a pulsed laser beam concurrently with application of an external magnetic field which is modulated in accordance with the information to be recorded. The layers may have equal Curie temperatures if they behave thermally asymmetrically. At any scanning position of the write spot the scanned superposed local areas of the two recording layers are heated thereby above the Curie temperature of at least one of such layers and then permitted to cool while being subjected to the external magnetic field. This produces a frozen-in net magnetization in the scanned local area of one of the recording layers, which aids the external magnetic field in producing a similar frozen-in net magnetization of the superposed local area in the other recording layer. This allows use of a relatively weak external magnetic field, which is more economical and capable of operation at higher frequencies. Any pre-existing magnetization of the latter superposed local area is erased in consequence of magnetization thereof in accordance with the external magnetic field.
REFERENCES:
patent: 4878132 (1989-10-01), Aratani
patent: 4922454 (1990-05-01), Taki
patent: 5069984 (1991-12-01), Hatwar et al.
patent: 5105400 (1992-04-01), Kikitsu
Jacobs Bernardus A. J.
Spruit Johannes H. M.
Eason Leroy
Nguyen Hoa
U.S. Philips Corporation
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