Improvement in recording power sensitivity for overwritable MO media by RE-rich GdNdFeCo control layer

For improvement in recording power sensitivity in overwritable magnetooptic media with exchange coupled trilayer (ECTL), it has been found necessary to decrease the saturation magnetization (M_s) value for the control layer, as well as to reduce the Curie temperature (T_c) value for the writing layer. Highly rare-earth (RE) rich GdNdFeCo film has been used to decrease the M_s value for the control layer, instead of ferromagnetic NdFeCo film. The media consists of a PC substrate, a SiN underlayer, a transition-metal-rich TbFe memory layer, a NdFeCo or highly RE-rich GdNdFeCo control layer, an RE-rich GdNdFeCo writing layer whose compensation temperature is 180°C, and an SiN protective layer. By using the RE-rich GdNdFeCo control layer and the lower T_c writing layer, the recording power sensitivity was improved 1.5 times compared to the media with NdFeCo control layer without decreasing the carrier-to-noise ratio