Abstract: This invention relates to a magnetooptical recording medium that is capable of direct overwriting by light intensity modulation without using a separate source for generating an external magnetic field and that has four magnetic layers superposed on a substrate, wherein said magnetic layers has vertical magnetic anisotropy and any two adjacent layers being bound by exchange force. The medium is characterized in that a fifth magnetic layer not bound by exchange force is provided over the fourth magnetic layer or that a layer made of a rare earth element/transition metal alloy in which the magnetization of rare earth elements is dominant is provided between the first and second magnetic layers which are bound together by exchange force.

Abstract: Information on a spinning magneto-optic disk is overwritten by illuminating a spot on a track on the disk with an erasing beam in the presence of a biasing magnetic field, and illuminating another spot on the same track with a writing beam during the same revolution of the disk. The erasing beam and writing beam can be focused through the same lens. The erasing beam erases all bits to the same known value, so it is not necessary to control the writing beam according to the old values of the bits. Benefits include simpler control logic and less stringent positioning requirements than in the past.