Method for reproducing information data from magneto-optical recording medium using linear polarized beam

A method for reproducing write-once information from an optical disk (a) comprising a disk substrate, and a recording layer on the disk substrate, the recording layer including a magnetic film with a magnetic anisotropy in a direction perpendicular to a surface of the magnetic film;

• and (b) capable of storing write-once information formed by first recording areas and second recording areas in a pre-determined portion of said recording layer, the first and second recording areas having different magnetic anisotropies in a direction perpendicular to a surface of the magnetic film;
• the method comprising:
• irradiating linearly polarized laser light onto said pre-determined portion;
• and
• detecting a rotational change in a polarization orientation of light reflected from the optical disk or light transmitted through the optical disk, the rotational change being caused depending on which of the first recording area and the second recording area is irradiated with the linearly polarized laser light, the rotational change occurring between +θk and approximately 0.