PURPOSE: To allow overwriting even if there are no magnets for initialization by forming an auxiliary layer as a layer which does not make magnetization inversion even at the time of recording, providing a magnetic field gradient in the magnetic field to be impressed and utilizing the difference in temp. drop between the high power and low power of a laser power at the time of the recording.
CONSTITUTION: An electromagnet 3 for generating a bias magnetic field is placed at x4 with respect to a condensing position x0. The magnetic field generated at this time forms the magnetic field intensity distribution having the magnetic field gradient which has the max. value at x4. The temp. distribution of the medium is the case of the temp. TH after the irradiation with the high power and the case of the temp. TL after the irradiation with the low power. The film temp. attains TH at x0 and thereafter, the temp. falls at the time of the irradiation with the high power. Since the Curie temp. Tc1 of the 1st layer 13 is lower than TH, the direction of the magnetization tends to be directed to the direction determined by the 2nd layer 14 but the direction of the magnetization is determined by the bias magnetic field. On the other hand, the magnetization of the 1st layer 13 is determined at the magnetization direction of the 2nd layer 14 at the time of the irradiation with the low power. There is no need for subsequent initialization of the 2nd layer 14 as mentioned above and the overwriting is possible.
NIIHARA TOSHIO
MIYAMOTO JIICHI
MIYAMOTO MAKOTO
OTA NORIO
HITACHI MAXELL