| 摘要 |
PURPOSE:To improve the utilizing efficiency of energy by providing plural number of bias magnetic field generating means, irradiating light beam while applying a bias magnetic field to a recording medium so as to record and erase the information. CONSTITUTION:A recording disc medium 1 having a vertical magnetization film is rotated around the rotational shaft in the vertical direction by a spindle motor 1. A laser beam source 3 and an objective lens 4 are mounted in an optical head 5 movable reciprocatingly along the radial direction of the medium 1. Electromagnets 6a-6c being bias magnetic field generating means are arranged along the reciprocating path of the head 5 at the opposite side to the head 5 with respect to the medium 1. A laser beam 7 from the beam source 3 forms a spot on the magnetization film of the medium 1. Further, the electromagnets 6a-6c are directed upward or downward with a magnetic field of a prescribed strength in the vicinity of the optical beam spot irradiating position of the medium 1 at recording or erasure. Thus, the utilization efficiency of energy is improved.
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