G - Physics – 11 – B
Patent
G - Physics
11
B
G11B 7/24 (2006.01)
Patent
CA 2173631
A magneto-optical recording apparatus records information on a magneto-optical recording medium composed of memory layer, writing layer and initializing layer which are disposed on a substrate, each comprising a magnetic thin film of amorphous-rare-earth transition-metal alloy. The layers are magnetically coupled directly, or through an intermediate layer therebetween, to each other under an exchange force. The magnetization of the initializing and writing layers is aligned in a single direction. The initializing layer has its compensation temperature, Tcomp3, and its magnetization of the TM subnetwork, Mtm3, is antiparallel to that of the RE subnetwork, Mre3. The netmagnetic moment of the initializing layer, Ms3, exhibited by the material is the vector sum of the two antiparallel subnetwork magnetizations, Ms3 = Mre3 + (-Mtm3). The Curie temperature of the three layers ( Tc1, Tc2, Tc3 ), and the temperature T31 at which the RE-rich antiparallel RE-TM magnetization of the initializing layer is copied to writing layer, and the temperature T32 at which the TM-rich antiparallel RE-TM magnetization of the initializing layer is copied to writing layer are ordered as follows: T31 < Tc1 < Tc2 < T32 < Tc3 In order to write a "1", the film temperature raised to the Curie temperature of the writing layer, Tc2, which is above the Curie temperature of the memory layer, Tc1, and above the compensation temperature of initializing layer, Tcomp3, so the direction of the net moment of initializing layer, Ms3, is changed from RE-rich magnetization to the opposite directed TM-rich magnetization, when the temperature falls below Tc2, at the temperature T32, which is above Tcomp3, the sublattice TM-rich magnetization of the initializing layer is copied to the writing layer, and at the temperature dropped below Tc1 the exchange coupling causes the sublattice magnetization of the writing layer to be copied to the memory layer - that is, a "1" is written. At the further dropped temperature T31, which is below Tcomp3, the RE-rich sublattice magnetizaion of initializing layer is copied to the writing layer, however, this magnetization is not copied to the memory layer. The sublattice magnetization of the writing layer and the net magnetization of the initializing layer are in the same (Mre3) direction, regardless of their past states. In order to write "0", the film temperature is raised to the vicinity of Tc1, then, when the temperature falls, the sublattice magnetization of the writing layer is copied to the memory layer - that is, a "0" is written.
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