Direct overwrite method by light intensity modulation using only an external magnet is described. The film consists of exchange-coupled RE-TM alloy quadrilayer. Good recording characteristics were obtained, such as C/N ratio>47 dB on a bit length= 0.76μm without a residual signal. The initializing process of the 2nd layer is one of the most important ones. It was found through M-H loops that the 2nd layer has two different coercivities for the magnetization states of other layers and coercivity of the 2nd layer is smaller than that of the single layer in the case where the sub-lattice magnetization of the 1st layer is anti-parallel to the 4th layer. Therefore, these phenomena assist the 2nd layer to be initialized.
